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+The Project Gutenberg EBook of Natural History of Cottonmouth Moccasin,
+Agkistrodon piscovorus (Reptilia), by Ray D. Burkett
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Natural History of Cottonmouth Moccasin, Agkistrodon piscovorus (Reptilia)
+
+Author: Ray D. Burkett
+
+Release Date: December 15, 2011 [EBook #38308]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK NATURAL HISTORY OF ***
+
+
+
+
+Produced by Chris Curnow, Joseph Cooper and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+
+Transcriber's Note.
+
+[=X] in Table 12 represents "x bar" or "x overbar" (the mean value).
+
+Hyphenation has been standardised save for the contents of 'Literature
+Cited' and the 'List of Publications.'
+
+
+
+
+  =================================
+
+  UNIVERSITY OF KANSAS PUBLICATIONS
+  MUSEUM OF NATURAL HISTORY
+
+  Vol. 17, No. 9, pp. 435-491, 7 figures in text
+  ------------ October 27, 1966 ----------------
+
+  Natural History of Cottonmouth Moccasin,
+  Agkistrodon piscivorus (Reptilia)
+
+  BY
+
+  RAY D. BURKETT
+
+  UNIVERSITY OF KANSAS
+  LAWRENCE
+  1966
+
+
+
+
+  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
+
+
+  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
+  Frank B. Cross
+
+  Volume 17, No. 9, pp. 435-491, 7 figures in text
+  Published October 27, 1966
+
+  UNIVERSITY OF KANSAS
+  Lawrence, Kansas
+
+  PRINTED BY
+  ROBERT R. (BOB) SANDERS, STATE PRINTER
+  TOPEKA, KANSAS
+  1966
+
+[Illustration: Printer's Logo]
+
+  31-4629
+
+
+
+
+  Natural History of Cottonmouth Moccasin,
+     Agkistrodon piscivorus (Reptilia)
+
+  BY RAY D. BURKETT
+
+
+
+
+CONTENTS
+
+
+                                                                PAGE
+     INTRODUCTION                                                439
+     ACKNOWLEDGMENTS                                             440
+     SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION                   441
+     DESCRIPTION                                                 444
+       Color and Pattern                                         444
+       Scutellation                                              444
+       Dentition                                                 449
+     HABITAT AND LIMITING FACTORS                                450
+     REPRODUCTION                                                452
+       Courtship and Mating                                      452
+       Reproductive Cycles                                       452
+       Embryonic Development                                     454
+       Birth of Young                                            454
+       Number of Young per Litter                                454
+       Population Composition                                    455
+       Reproductive Potential                                    455
+     GROWTH AND DEVELOPMENT                                      456
+       Size at Birth and Early Growth                            456
+       The Umbilical Scar                                        457
+       Later Growth and Bodily Proportions                       457
+     SHEDDING                                                    459
+       The Shedding Operation                                    459
+       Frequency of Shedding                                     460
+     FOOD HABITS                                                 461
+       Methods of Obtaining Prey                                 461
+       Food and Food Preferences                                 462
+     MORTALITY FACTORS                                           465
+       Natural Enemies and Predators                             465
+       Parasites and Diseases                                    465
+       Miscellaneous Causes of Death                             466
+     BEHAVIOR                                                    466
+       Annual and Diel Cycles of Activity                        466
+       Basking                                                   469
+       Coiling                                                   469
+       Locomotion                                                470
+       Disposition                                               470
+       Defense and Escape                                        471
+       "Head Bobbing"                                            471
+       Combat Dance                                              472
+     THE VENOM                                                   473
+       Properties of the Venom                                   473
+       Venom Yield and Toxicity                                  473
+       Susceptibility of Snakes                                  475
+     THE BITE                                                    476
+       Effects of the Bite                                       476
+       Treatment                                                 477
+       Case History of a Bite                                    479
+       Snakebite in the United States                            480
+     SUMMARY                                                     480
+     LITERATURE CITED                                            485
+
+
+
+
+INTRODUCTION
+
+
+Objectives of the study here reported on were to: (1) learn as much as
+possible concerning the natural history and economic importance of the
+cottonmouth; (2) determine what factors limit its geographic
+distribution; (3) determine the role of the cottonmouth in its
+ecological community; and (4) compare the cottonmouth's life history
+with that of other crotalid snakes, especially the kinds that are most
+closely related to it.
+
+Twenty-five live cottonmouths were kept in the laboratory for the
+purpose of studying behavior and fang shedding and for comparison of
+measurements with those of preserved specimens. Live snakes were
+obtained in Brazoria and Nacogdoches counties, Texas, from Hermann Park
+Zoo, Houston, Texas, and from the late Paul Anderson of Independence,
+Missouri. Preserved western cottonmouths were examined for the purpose
+of determining variation, distribution, food habits, body proportions,
+embryonic development, and reproductive cycles. The cottonmouths
+examined include: 221 from Texas; 33 from Arkansas; 22 from Louisiana; 2
+from Illinois; and 1 each from Kansas, Mississippi, and Oklahoma.
+
+In the preparation of this report I have examined all available
+literature pertaining to the cottonmouth and have drawn from these
+sources for comparative or additional material. Some of the more
+noteworthy contributions to knowledge of the cottonmouth are the general
+accounts of the life history by Allen and Swindell (1948), Barbour
+(1956), and Wright and Wright (1957); the publications by Gloyd and
+Conant (1943) concerning taxonomy; Klimstra (1959) concerning food
+habits; and Allen (1937), Parrish and Pollard (1959), Swanson (1946),
+and Wolff and Githens (1939b) concerning the venom. Numerous other
+publications, although brief, contain worthwhile contributions. Also of
+special interest as a source of material for comparison of cottonmouths
+with other crotalids are the works of Fitch (1960) on the copperhead and
+of Klauber (1956) on the rattlesnakes.
+
+The cottonmouth has been well known for nearly 200 years. Wright and
+Wright (1957) listed the following vernacular names that are applied to
+the cottonmouth: black moccasin, black snake, blunt-tail moccasin,
+congo, copperhead, cottonmouth water moccasin, cotton-mouthed snake,
+gapper, highland moccasin, lowland moccasin, mangrove rattler, moccasin,
+North American cottonmouth snake, North American water moccasin, North
+American water viper, pilot, rusty moccasin, salt-water rattler,
+stubtail, stump (-tail) moccasin, stump-tail viper, swamp lion, Texas
+Moccasin, trapjaw, Troost's moccasin, true horn snake, true water
+moccasin, viper, water mokeson, water pilot, water rattlesnake, and
+water viper.
+
+Some of the names listed above are based upon superstition and folklore
+prevailing in pioneer times, and others are based upon the behavior or
+appearance of the snake at various ages. Names like "stump-tail
+moccasin" are derived from the appearance of females which have short
+tails or snakes that have lost part of the tail. Names like "gapper" and
+"trapjaw" came to be applied because of the habit of the snake's lying
+with its mouth open when approached. The name "cottonmouth" also was
+derived from this behavior, although the lining of the mouth is whitish
+in most other snakes. The term "rattlesnake" may have come from the fact
+that the cottonmouth vibrates its tail vigorously when nervous as do
+many other snakes, or it may have been confused with rattlesnakes.
+Because of the general public's fear of snakes and their reluctance to
+learn to discriminate between the poisonous and harmless species,
+numerous kinds of snakes seen in or near water have been called
+moccasins. The general appearance, pugnacious behavior, and whitish
+mouth of water-snakes (_Natrix_) have earned them a bad reputation. In
+fact, a great majority of the "cottonmouths" reported in many areas are
+found to be water-snakes.
+
+The cottonmouth is economically important mainly because of the
+injurious or fatal effects of its bite and the psychological effect that
+its actual or suspected presence has upon many persons. The species eats
+a wide variety of prey items and helps to prevent overabundance of
+certain kinds of organisms. The venom has been used in the therapeutic
+treatment of blood clots owing to its anticoagulant properties
+(Didisheim and Lewis, 1956). It also is employed in the treatment of
+haemorrhagic conditions and rheumatoid arthritis, as well as in the
+production of antivenin (Allen and Swindell, _op cit._:13). None of
+these uses of venom has become widely accepted, and its value is
+questionable.
+
+
+
+
+ACKNOWLEDGMENTS
+
+
+For guidance in the course of my study, I am especially indebted to
+Professor Henry S. Fitch. For suggestions concerning the preparation of
+the manuscript, I thank Professor E. Raymond Hall. I am grateful to my
+wife, Janis, for her invaluable assistance and for typing the
+manuscript.
+
+For use of specimens in their care, I thank Professors William E.
+Duellman, University of Kansas; Robert L. Packard, formerly of Stephen
+F. Austin State College; W. Frank Blair, University of Texas; and
+William B. Davis and Richard J. Baldauf, Texas Agricultural and
+Mechanical College. Mr. John E. Werler of the Hermann Park Zoo, Houston,
+Texas, contributed live individuals; Mr. Richard S. Funk contributed
+information on the birth of a brood of cottonmouths; and Dr. Henry M.
+Parrish contributed information on the incidence of snakebite. To
+numerous other persons at leading museums throughout the United States
+for information on the cottonmouths in their collections, to all who
+helped with the field work in various ways, and to others at the
+University of Kansas for their help and suggestions I am grateful.
+
+
+
+
+SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION
+
+
+Snakes of the genus _Agkistrodon_ are relatively primitive members of
+the Crotalidae, which is one of the most specialized families of snakes.
+A majority of the pit-vipers are found in the Americas, but close
+relatives are found from extreme southeastern Europe through temperate
+Asia to Japan (_A. halys_) and southeastern Asia including Indonesia
+(_Agkistrodon_ and _Trimeresurus_). Familial characters include:
+vertical pupil of the eye; facial pit present between the preoculars and
+loreal; scales usually keeled; short, rotatable maxilla bearing a large
+hollow fang; toothless premaxilla; chiefly hematoxic venom; and
+undivided anal plate.
+
+The genus _Agkistrodon_ includes about nine species in the Old World and
+three in North and Central America. Some of the primitive characters of
+the genus are: head covered with nine enlarged shields or having the
+internasals and prefrontals broken up into small scales; subcaudals on
+proximal part of tail undivided; fangs relatively short; tail lacking
+rattles. In one species, _A. rhodostoma_, the scales are smooth; and the
+female is oviparous and guards her eggs until they hatch. Other species
+have keeled scales and are ovo-viviparous.
+
+There is little paleontological evidence illustrating evolution of the
+cottonmouth or for that matter of crotalids in general. Brattstrom
+(1954) summarized the current knowledge of fossil pit-vipers in North
+America. The few fossils found of the cottonmouth are from Alacha,
+Brevard, Citrus, Levy, Pasco, and Pinellas counties, Florida
+(Brattstrom, _op. cit._:35; Auffenberg, 1963:202). All are of late
+Pleistocene Age and well within the present geographic range of the
+cottonmouth.
+
+Of crotalid genera only _Agkistrodon_ occurs in both the Old World and
+the New World, suggesting that this genus is relatively old. Schmidt
+(1946: 149-150) mentioned several other closely related groups of
+animals found in both eastern Asia and eastern North America, including
+the reptilian genera: _Natrix_, _Opheodrys_, _Elaphe_, _Ophisaurus_,
+_Leiolopisma_ (= _Lygosoma_), _Eumeces_, _Clemmys_, _Emmys_, and
+_Alligator_. Of the groups of animals now confined to these two regions
+the most important are the cryptobranchid salamanders, the genus
+_Alligator_, and the spoon-bills (_Psephurus_ in China and _Polyodon_ in
+the Mississippi drainage). Fossil evidence for these groups indicates
+that existing forms common to eastern Asia and eastern North America are
+remnants of a late Cretaceous or early Tertiary Holarctic fauna which
+was forced southward as the climate became gradually cooler to the
+north. "Other clues suggest that both _Agkistrodon_ and _Trimeresurus_
+(_Bothrops_) moved from Asia to America, one of these presumably giving
+rise to the rattlesnakes." (Darlington, 1957:228).
+
+The named, American kinds of _Agkistrodon_ currently are arranged as
+three species: the copperhead, the cantil and the cottonmouth. The
+copperhead (_A. contortrix_) is divided into four subspecies, all of
+which are terrestrial. This species occurs from southern New England to
+eastern Kansas and along the Atlantic and Gulf Coastal plains, exclusive
+of peninsular Florida and the delta of the Mississippi River in
+Louisiana. It extends southwest from Kansas through the Edwards Plateau
+of west-central Texas. Isolated populations occur in the Chisos and
+Davis mountains of Trans-Pecos Texas. The cantil or Mexican moccasin
+(_A. bilineatus_), probably the nearest relative of the cottonmouth (_A.
+piscivorus_), is divisible into two subspecies and occupies a nearly
+complementary range from Mexico south to Nicaragua. The cottonmouth
+occurs throughout the coastal plains of the southeastern United States,
+usually at altitudes of 500 feet or less. Two subspecies are recognized,
+the eastern _A. p. piscivorus_ and the western _A. p. leucostoma_. A
+revision of the genus is underway by Professor Howard K. Gloyd.
+
+The basic pattern and various behavioral traits are common to all three
+species. The young are more nearly alike in appearance than adults, the
+copperhead and the cottonmouth being easily confused. Adults differ in
+color, size, body proportions, habitat, and habits. In range and habitat
+preference the cottonmouth more closely resembles the southern
+subspecies of the copperhead, _A. c. contortrix_, which is usually found
+in lowlands, near swamps and streams, but seldom in water.
+
+[Illustration: FIG. 1.]
+
+FIG. 1. Geographic range of the cottonmouth, showing marginal and
+near-marginal records, based largely upon maps by Gloyd and Conant
+(1943:165) and Conant (1958:336) but including additional records. The
+more important of these records (from east to west) are discussed in the
+following paragraphs. Crosshatching indicates the area of intergradation
+between the eastern and western subspecies. Old records, indicated by
+dates, and their sources are as follows: 1850's and 1891--U. S. National
+Museum numbers 4263 and 32753 respectively; 1897--Hurter (1897); and
+1895--Stejneger (1895:408).
+
+The northernmost record for the eastern subspecies is in the Petersburg
+area, Prince George County, Virginia (Anon., 1953:24). A sight record
+(Hickman, 1922:39) near Bristol, West Virginia, probably was based on a
+water-snake (_Natrix_ sp.), since the stream in which the snake was seen
+flows north into the Ohio River rather than southeast through Virginia.
+In North Carolina the most inland record is from the Neuse River, six to
+eight miles east of Raleigh (Stejneger, 1895:408). Neill (1947:205)
+reported a population in the vicinity of Dry Fork Creek on the boundary
+line of Wilkes and Oglethorpe counties, Georgia. Distribution of
+cottonmouths in Florida is statewide, including the Keys and other
+offshore islands.
+
+The ranges of the two subspecies, _piscivorus_ and _leucostoma_, meet
+near the eastern border of Mississippi. _A. p. piscivorus_ has been
+reported from Tishomingo County to the Gulf and east of the Loess Bluff
+area in central Mississippi, and _A. p. leucostoma_ has been reported
+from this area westward. A few specimens from along the Coast indicate
+intergradation (Cook, 1962:33) between the two subspecies.
+
+Barbour (1956:33) reported one specimen from Cypress Creek, in the Green
+River drainage, Muhlenberg County, Kentucky, and stated that suitable
+habitat can be found in several areas east of Kentucky Lake. Hence,
+cottonmouths may have entered this area via the Ohio River. Stejneger
+(_loc. cit._) reported the species in the Wabash River at Mount Carmel,
+Wabash County, Illinois, and mentioned a former occurrence at Vincennes,
+Knox County, Indiana; but there are no recent records at these
+localities. Hurter (1897) reported having seen cottonmouths in Illinois,
+opposite St. Louis; Smith (1961:265) believes that this and a population
+in Monroe County, Illinois, are isolated relicts, since no specimens
+have been found within 50 miles to the south of Monroe County. The
+specimens reported by Anderson (1941:178; 1945:274) near Chillicothe
+(three miles southwest and seven miles northwest, respectively),
+Livingston County, Missouri, also are thought to represent a relict
+population. Hall and Smith (1947:453) reported one specimen from Jasper
+County, Missouri, in the Spring River which flows through extreme
+southeastern Kansas and into Oklahoma and another in the Neosho River at
+Chetopa, Kansas. Both of these specimens were taken after a flood, and
+no additional specimens have been taken in this region. Nevertheless,
+sufficient habitat is probably available along the Neosho and Verdigris
+rivers in the southeastern part of Kansas.
+
+In Texas the cottonmouth has penetrated marginal habitat perhaps farther
+than anywhere else in its range. Formerly it was thought to be limited
+to the country east of the Balcones Escarpment (Smith and Buechner,
+1947:8), but semiarid areas of the state have been invaded primarily via
+the Colorado and Brazos River systems up to altitudes of 2300 feet. Two
+additional specimens are said to have been collected along the Rio
+Grande. Dr. Howard K. Gloyd (_in litt._) stated that the specimen
+reported from Eagle Pass, Maverick County, is believed to have been
+taken in the 1850's; and the one said to have come from the mouth of the
+Devil's River is actually marked "near Santa Rosa, Cameron County,
+September 30, 1891." No additional specimens have been taken in that
+area; and the range now probably extends no farther south than Corpus
+Christi, Texas. Brown's (1903:554) knowledge of the extension of the
+range of the cottonmouth west of longitude 98° is probably based upon
+the records along the Rio Grande reported in the nineteenth century.
+
+Three extensions of the known range in Texas are reported herein. One
+specimen was captured by Mr. Harry Green (HWG 346) along the San Saba
+River, 8.1 miles west of Menard, Menard County. The other two specimens
+(KU 84375 and 84376) were taken by the late Paul Anderson one and
+one-half miles north of Pecan Crossing, South Concho River, Tom Green
+County, and one mile west of Mertzon, Irion County.
+
+In the hypsithermal period following Pleistocene glaciation,
+cottonmouths gradually moved northward occupying areas beyond their
+present range. The distributional records since the 1850's and the
+apparent relict populations now in existence indicate that the range
+of this species has since receded.
+
+
+
+
+DESCRIPTION
+
+Color and Pattern
+
+
+Color predominantly brown, ranging through pale reddish-brown or dark
+reddish-brown, brownish-green, to almost black; 10 to 17 irregular dark
+brown bands on paler brown ground color; young paler (some nearly salmon
+pink), retaining a vivid pattern throughout first year; pattern of most
+individuals nearly obliterated by third year; brilliance and dullness of
+predominant color correlated with molting cycle (skin especially bright
+and shiny immediately following shedding); tip of tail yellowish in
+juveniles; posterior part of venter and tail uniformly black in some
+adult individuals, especially females; secondary sexual differences in
+dorsal coloration, such as found in copperhead by Fitch (1960:102), not
+noted.
+
+The eastern subspecies, _A. p. piscivorus_, has the more brilliant
+pattern in which the centers of the dark cross-bands are invaded by the
+ground color. The cross-bands are slightly constricted in the mid-line
+and may or may not be bilaterally symmetrical. One-half of the
+cross-band may be displaced anteriorly or posteriorly to a slight degree
+or may even be completely absent. From one to several dark spots may be
+present within the cross-bands.
+
+The western subspecies, _A. p. leucostoma_, has a comparatively dull
+pattern in which the ground color does not invade the center of the
+cross-bands. In many instances the bands are outlined by white scales,
+as in the Mexican moccasin (this character is not so prominent in _A. p.
+piscivorus_ because of the paler ground color). A large, dark blotch
+usually occurs at the base of the cross-band and may completely cross
+the ventral scales. The characteristic variations found in _piscivorus_
+are also present in _leucostoma_.
+
+The number of bands is often difficult to count because of the dark
+color of some specimens. Gloyd and Conant (1943:168) reported averages
+of 12.5 (11 to 16) and 12.2 (10 to 16) in males and females,
+respectively, of _leucostoma_ and ranges of 10 to 17 for males and 10 to
+16 for females with averages of 13 in both sexes of _piscivorus_. On 20
+specimens of _leucostoma_ from Texas the average number of bands was
+12.7 (11 to 15). If the number of bands differed on the two sides of an
+animal, the total number of the two sides was divided by two.
+
+
+Scutellation
+
+The scutellation of the cottonmouth closely resembles that of the other
+species of _Agkistrodon_. For example, the nine cephalic shields are
+characteristic of most species of _Agkistrodon_, as well as most other
+primitive crotalids and viperids, and most colubrids. Most individuals
+have an additional pair of large scales behind the parietals.
+
+The numbers of postoculars, supralabials, and infralabials are variable.
+On either side the postoculars (three in most specimens) are reduced to
+two in some specimens. The supralabials (eight in most specimens)
+frequently vary (usually on one side only) from seven to nine. The
+number of infralabials is somewhat more variable than the number of
+supralabials, the usual number being 11, but 10 is also common; 8, 9,
+and 12 are more rare (Table 1). In 102 snakes in which these characters
+were examined, four different combinations of supralabials and seven
+combinations of infralabials were found. Both characters together
+yielded 16 combinations, considering only the actual number of scales
+and not taking into account the side of the head on which they occurred
+(Table 2). The combinations found in a brood of seven young from
+Houston, Texas, are shown in Table 3 to illustrate the variability of
+this character. Gloyd and Conant (1943:168) found a variation of 6 to 11
+(8) and 7 to 9 (8) supralabials and 8 to 13 (11) and 8 to 12 (10.4)
+infralabials in samples of 301 _leucostoma_ and 119 _piscivorus_,
+respectively (numbers in parentheses represent average). Also of
+interest is the variability of the scales themselves. In one instance a
+scale was found that had not completely divided. In another specimen the
+last supralabial and last infralabial were one scale that completely
+lined the angle of the jaw. Instances of one scale almost crowding out
+another were common. In still other instances one or two supralabials
+were divided horizontally into two scales. Individual variation rather
+than geographical variation occurs in these characters.
+
+     TABLE 1.--Frequency of Occurrence of Various Numbers of
+     Supralabial and Infralabial Scales in 102 Cottonmouths.
+
+      ====================================================
+     |          |Specimens  |Specimens |      |           |
+     |Number    |having     |having    |Total |Percentage |
+     |of scales |number on  |number on |      |           |
+     |          |both sides |one side  |      |           |
+     |----------------------------------------------------|
+     |                     Supralabials                   |
+     |----------------------------------------------------|
+     |    7     |    11     |    24    |  35   |   25.2   |
+     |    8     |    64     |    27    |  91   |   65.5   |
+     |    9     |     0     |    3     |   3   |    2.2   |
+     |----------------------------------------------------|
+     |                      Infralabials                  |
+     |----------------------------------------------------|
+     |    8     |     0     |    2     |   2   |    1.5   |
+     |    9     |     3     |    10    |  13   |    9.6   |
+     |    10    |    12     |    32    |  44   |   32.4   |
+     |    11    |    53     |    22    |  75   |   55.1   |
+     |    12    |     0     |    2     |   2   |    1.5   |
+      ----------------------------------------------------
+
+     TABLE 2.--Numbers of Supralabials and Infralabials of 102
+     Cottonmouths.
+
+      ===========================================
+     |  Number of  |  Number of   |  Number of   |
+     | individuals | supralabials | infralabials |
+     |     37      |      8       |      11      |
+     |     15      |      8       |    10-11     |
+     |     12      |     7-8      |      11      |
+     |      6      |     7-8      |    10-11     |
+     |      5      |      8       |      10      |
+     |      5      |      8       |     9-10     |
+     |      4      |      7       |      11      |
+     |      3      |      7       |     9-10     |
+     |      3      |     7-8      |      10      |
+     |      2      |      7       |      9       |
+     |      2      |      7       |      10      |
+     |      2      |      8       |    10-12     |
+     |      2      |     8-9      |      10      |
+     |      2      |     7-8      |     8-9      |
+     |      1      |     7-8      |      9       |
+     |      1      |     8-9      |    10-11     |
+      -------------------------------------------
+
+The dorsal scales of cottonmouths are strongly keeled except that those
+of the two lower scale-rows on each side are weakly keeled. Also they
+are slightly larger than the others. Two apical pits are present on each
+dorsal scale. The shape of the scales and number of scale rows vary
+depending upon the position on the body. Scales on the neck are
+considerably smaller than those elsewhere on the body and are arranged
+in two or three more rows than those at mid-body. The skin in the region
+of the throat, neck, and fore-body is especially elastic and allows the
+swallowing of large prey. Posteriorly from the mid-body the scales
+decrease in size and become more angular, those on the tail tending to
+be rhomboidal and wider than long. In the region of the anus the number
+of scale rows diminishes rapidly, leaving only 12 to 14 rows at the base
+of the tail and only three rows immediately ahead of the tail tip. The
+tail ends in a spine composed of two scales: one scale covers the
+bottom, lower parts of the sides, and tip of the spine; and a shorter
+dorsal scale covers the top and upper parts of the sides of the basal
+two-thirds of the spine. The spine of embryos and young cottonmouths is
+blunt, but is pointed in most adults.
+
+     TABLE 3.--Variation in Numbers of Supralabials and Infralabials
+     in a Brood of Seven Cottonmouths.
+
+     ===========================================
+    |  Number of  |  Number of   |  Number of   |
+    | individuals | supralabials | infralabials |
+    |      1      |      7       |      9       |
+    |      1      |      7       |     9-10     |
+    |      2      |     7-8      |     8-9      |
+    |      1      |     7-8      |      9       |
+    |      1      |      8       |     9-10     |
+    |      1      |     8-9      |      10      |
+     -------------------------------------------
+
+     TABLE 4.--Analysis of Number of Scale Rows at Three Parts of
+     the Body in 81 Cottonmouths.
+
+   ==============================================================
+  |        |       Neck      |     Mid-body    | Anterior to anus|
+  |        |--------+--------+--------+--------+--------+--------|
+  | Number | Number |  Per-  | Number |  Per-  | Number |  Per-  |
+  |   of   |   of   |centage |   of   |centage |   of   |centage |
+  | scales |indivi- |        |indivi- |        |indivi- |        |
+  |per row | duals  |        | duals  |        | duals  |        |
+  |--------+--------+--------+--------+--------+--------+--------|
+  |   29   |    1   |   1.2  |  ...   |  ...   |  ...   |  ...   |
+  |   28   |    3   |   3.7  |  ...   |  ...   |  ...   |  ...   |
+  |   27   |   52   |  64.2  |  ...   |  ...   |  ...   |  ...   |
+  |   26   |   16   |  18.0  |    2   |   2.5  |  ...   |  ...   |
+  |   25   |    8   |   9.9  |   67   |  82.7  |  ...   |  ...   |
+  |   24   |    1   |   1.2  |    4   |   4.9  |  ...   |  ...   |
+  |   23   |  ...   |  ...   |    8   |   9.9  |    4   |   4.9  |
+  |   22   |  ...   |  ...   |  ...   |  ...   |    4   |   4.9  |
+  |   21   |  ...   |  ...   |  ...   |  ...   |   68   |  84.0  |
+  |   20   |  ...   |  ...   |  ...   |  ...   |    5   |   6.2  |
+   --------------------------------------------------------------
+
+The number of scale rows on the neck, at mid-body, and just anterior to
+the anus is relatively constant at 27-25-21, respectively; but some
+individual variation is evident (Table 4). Since the rows are diagonally
+arranged, it is necessary in counting scales to proceed either
+anteriorly or posteriorly across the back; or the row may be counted in
+either direction up to the center of the back and then reversed on the
+other side of the snake. In order to count the scale rows in a position
+where no scale reduction or addition was occurring and to avoid as much
+error as possible, I counted from anterior to center and back on the
+neck, in any direction at mid-body, and from posterior to center and
+back near the anus. Because females generally are the larger in
+circumference posteriorly, they could have more scale rows than males
+just anterior to the anus. The few snakes having more than 21 scale rows
+in the posterior region offer no conclusive evidence as to tendencies,
+but in both instances in which this occurred the females outnumbered the
+males three to one. An odd, rather than an even, number of scale rows
+occurs on most of the length of the snakes examined, because there is a
+mid-dorsal row and scale rows tend to be lost on both sides at about the
+same level. An example of scale reduction of one snake was as follows:
+
+      6+7 (13)                  6+7 (96)
+   27 --------  25 --------  24 --------   23 ---------  22 ---------
+      5+6 (13)     5+6 (90)                   7+8 (111)     7+8 (114)
+
+                                6+7 (122)                  +7, -5 (125)
+   23 --------  22 --------  23 ---------  21 --------  22 ------------
+      -6 (118)     +6 (119)     6+7 (121)     +6 (123)
+
+      -6 (126)
+   22 --------  21 (130).
+
+This scale reduction follows the method proposed by Dowling (1951b: 133)
+in which the numbers on the mid-line represent the number of scale rows,
+upper figures refer to the right side of the snake, and figures in
+parentheses indicate the number of the ventral scale (counted from the
+anterior end of the series), thus marking the position of the addition
+or reduction. Addition of a row is shown by a plus sign and the number
+of the row, whereas reductions are shown by a minus sign and the number
+of the row that is lost or by a plus sign between the number of two rows
+that join. According to Dowling, variation in number of dorsal scales
+characterizes the few genera and species of snakes in which it has been
+studied. The time and difficulty involved in ascertaining the number of
+scales explain why it has not been widely used in classification.
+
+[Illustration: FIG. 2. Number of ventral scales in 48 female and 34
+male _A. p. leucostoma_.]
+
+Ventral scales on 34 males averaged 134.4 (128 to 139), and on 48
+females 133.5 (128 to 137) (Fig. 2.). Barbour (1956:34) found an average
+of 135.3 ventral scales on 64 males and 44 females, and Gloyd and Conant
+(_loc. cit._) found an average of 134 for both males and females. The
+average for the eastern cottonmouth obtained by Gloyd and Conant,
+however, was 137 ventrals in both sexes. Some of my counts were made
+before I knew of the standard system of counting ventrals proposed by
+Dowling (1951a:97-99), in which the first ventral plate is defined as
+the most anterior one bordered on both sides by the first row of
+dorsals. Therefore, some inconsistencies may exist in my counts. Where
+differences occur, Dowling's method probably will indicate the presence
+of an additional scale, since it appears to begin farther anteriorly on
+the average, than I began counting.
+
+[Illustration: FIG. 3. Number of caudal scales in 44 female and 34
+male _A. p. leucostoma_.]
+
+     TABLE 5.--Caudal Scale Combinations in 95 Cottonmouths.
+     U = Undivided; D = Divided.
+
+   =====================================================================
+          |                         Number of scales
+          |-------------------------------------------------------------
+   Number |   |     |     |   |    |   |    |   |     | |  | |  | | | |
+   of     |   |     |     |   |    |   |    |   |     | |  | |  | | | |
+   samples| D |  U  |  D  | U | D  | U |  D | U |  D  |U| D|U| D|U|D|U|D
+   -------+---+-----+-----+---+----+---+----+---+-----+-+--+-+--+-+-+-+-
+     25   |   |13-35|10-32|   |    |   |    |   |     | |  | |  | | | |
+     11   |1-2|12-33|14-28|   |    |   |    |   |     | |  | |  | | | |
+     20   |   |16-39| 1-9 |1-3|3-24|   |    |   |     | |  | |  | | | |
+     20   |1-4| 3-37| 1-21|1-5|1-29|   |    |   |     | |  | |  | | | |
+      4   |   |14-30| 1-8 |1-7|1-8 |1-4|2-10|   |     | |  | |  | | | |
+      3   | 1 |18-23| 1-2 |1-2|6-11|1-3|6-9 |   |     | |  | |  | | | |
+      4   |   | 1-17|   1 |1-3|1-8 |1-4|1-3 |1-4|13-22| |  | |  | | | |
+      2   |1-2| 4-16|   1 |1-4| 2  | 1 |1-4 | 1 |18-21| |  | |  | | | |
+      1   |   |  20 |   1 | 1 | 1  | 1 | 6  | 1 |  3  |1|11| |  | | | |
+      1   |   |  10 |   2 | 3 | 2  |10 | 1  | 2 |  2  |1| 4|4|  | | | |
+      1   |   |  20 |   1 | 1 | 2  | 1 | 1  | 4 |  4  |2| 4|1| 3| | | |
+      1   | 1 |  13 |   1 | 1 | 1  | 3 | 1  | 1 |  1  |4| 2|4|13| | | |
+      1   |   |  17 |   1 | 1 | 2  | 1 | 1  | 6 |  2  |1| 2|3| 2|7| | |
+      1   |   |   9 |   1 | 1 | 8  | 1 | 3  | 1 |  1  |3| 1|1| 2|1|1|1|6
+   ---------------------------------------------------------------------
+
+Analysis of caudal scales revealed sexual dimorphism. In the six
+specimens from Tennessee, Blanchard (1922:16) found the same thing.
+Caudals averaged 45.4 (41 to 50) on 34 males and 42.6 (39 to 49) on 44
+females (Fig. 3). Barbour (_loc. cit._) found an average of 45.7 (30 to
+54) caudals in males and 43 (17 to 56) in females. Caudal scale counts
+by Gloyd and Conant (_loc. cit._) averaged 44 (38 to 49) in males and 42
+(37 to 48) in females of _leucostoma_; in _piscivorus_ they averaged 48
+(42 to 53) in males and 44 (41 to 49) in females. Another
+seldom-mentioned, unusual characteristic of the caudal scales of
+copperheads and cottonmouths is that some are single (usually those at
+the base of the tail) and others divided (Table 5). To my knowledge, all
+other species have either single or divided scales the entire length of
+the tail. See Klauber (1941:73) and Fox (1948:252) concerning
+correlation of few scales with warm environment.
+
+
+Dentition
+
+Cottonmouths, like other pit-vipers, have their teeth reduced in number
+and have enlarged, highly specialized fangs. Small teeth occur on the
+palatine and the pterygoid in the upper jaw and on the dentary in the
+lower jaw. The dentary bone bears 17 curved teeth that decrease in size
+posteriorly. The palatine bears five small, strongly curved teeth, and
+the pterygoid bears 16 to 18 strongly curved teeth decreasing in size
+posteriorly. The numbers of teeth mentioned above in each instance refer
+to the number of sockets rather than the actual number of teeth, because
+teeth are frequently shed, leaving some of the sockets empty at any one
+time.
+
+The maxillary bone has two sockets side by side which bear the poison
+fangs, usually one at a time. During the period shortly before a fang is
+to be shed, however, its replacement becomes attached in the alternate
+socket; and both fangs may be functional for a short time. The old fang
+then becomes weakened at its base, eventually breaks off, and is
+swallowed. At any one time four or five replacement fangs in various
+stages of development are found in the gum behind the functional fang.
+These replacement fangs, which are arranged in alternate rows, gradually
+enlarge as they move forward in their development and, in juveniles, are
+generally slightly longer than the fangs that they replace.
+
+In 1963 I examined the fangs of 14 cottonmouths at four- to seven-day
+intervals for a period of six weeks. The fang-shedding cycle was found
+to be highly irregular, with a double condition (on one or both sides)
+occurring one-third of the time. Approximately the same proportion of
+double fangs was found in preserved individuals. A replacement period of
+at least five days was observed in one snake. One-half the cycle (from
+replacement on one side to replacement on the other) varied from five to
+twenty days, indicating that the cycles for each fang are independent of
+one another. Bogert (1943:324) found that young rattlesnakes are born
+with functional fangs in the two inner sockets. Nonsynchronous use of
+the sockets on opposite sides of the head in rattlesnakes is a later
+development which results from accidents or other conditions leading to
+a longer retention of the fang on one side than on the other (Klauber,
+1956:723). I found a double set of fangs in cottonmouths only twice in
+the six-week period. A complete cycle was recorded in ten instances in a
+period of 19 to 23 days and in two instances in 32 days. One cottonmouth
+was examined periodically over a 34-day period by Allen and Swindell
+(1948:12), but a complete fang-shedding cycle was not observed. Fitch
+(1960:110) reported a 33-day cycle in copperheads; Klauber (1956:726)
+estimated the normal active life of each fang of an adult rattlesnake to
+be from six to ten weeks, but he made no observations to confirm his
+estimation.
+
+Fangs measured from the tip of the notch of the basal lumen to the end
+of the fang vary from about 1.3 per cent of the snout-vent length in
+juveniles to about 1.0 per cent in large adults (Table 6). The fangs are
+longer than those of copperheads (Fitch, 1960:111). Klauber's (1956:736)
+figures on fang-lengths in all species of rattlesnakes are percentages
+of total length rather than of the snout-vent length. The fangs of
+various species of rattlesnakes range from nearly the same proportionate
+length as those of cottonmouths to some much longer.
+
+From patterns of bites of venomous snakes, Pope and Perkins
+(1944:333-335) attempted to correlate number, size, and patterns of
+tooth marks with size and generic identity of the snake responsible for
+the bite. Distance between fangs is relatively constant for snakes of a
+particular size (Table 6) regardless of genus, but the fangs of a
+cottonmouth are directed outward to variable degrees, and puncture
+wounds could easily resemble those of a much larger snake (Table 7).
+Also there is no direct relationship between size of snake and toxicity
+or amount of venom injected. Consequently information of this kind is of
+little or no value from a medical standpoint.
+
+     TABLE 6.--Correlation of Relative Fang-length and Distance
+     Between Fangs at Base with Snout-vent Length of Cottonmouths.
+
+   =======================================================
+  |Snout-vent    |Number |Average     |Number |Average    |
+  |length        |in     |ratio of    |in     |ratio of   |
+  |(millimeters) |sample |fang-length |sample |distance   |
+  |              |       |to          |       |between    |
+  |              |       |snout-vent  |       |fangs to   |
+  |              |       |length      |       |snout-vent |
+  |              |       |(percent)   |       |length     |
+  |              |       |            |       |(percent)  |
+  |--------------+-------+------------+-------+-----------|
+  |   200-299    |   3   |    1.33    |   3   |   2.57    |
+  |   300-399    |   7   |    1.30    |   5   |   2.48    |
+  |   400-499    |  13   |    1.21    |   9   |   2.21    |
+  |   500-599    |  12   |    1.22    |   8   |   2.19    |
+  |   600-699    |   7   |    1.17    |   1   |   2.10    |
+  |   700-799    |   5   |    1.07    |   4   |   1.65    |
+  |   800-899    |   1   |    1.00    |   1   |   2.00    |
+   -------------------------------------------------------
+
+     TABLE 7.--Contrast in Measurements Between the Base of the
+     Fangs and Between Fang Punctures of Nine Cottonmouths (in
+     millimeters).
+
+   ==================================================
+  | Distance between | Distance between | Snout-vent |
+  |  base of fangs   |  fang punctures  |   length   |
+  |------------------+------------------+------------|
+  |       7.7        |       13.0       |    400     |
+  |       8.7        |       14.0       |    575     |
+  |      10.0        |       22.5       |    526     |
+  |      11.0        |    18.0-19.0     |    590     |
+  |      12.0        |       18.0       |    793     |
+  |      13.0        |    17.0, 20.0    |  558, 612  |
+  |      15.5        |       23.5       |    800     |
+  |      16.0        |       24.0       |    800     |
+   --------------------------------------------------
+
+
+
+
+HABITAT AND LIMITING FACTORS
+
+
+Although usually associated with swamps and lowlands along river
+bottoms, the cottonmouth lives in a variety of habitats ranging from
+salt marshes to cool, clear streams and from sea level to an altitude of
+2300 feet. Shaded, moist areas either in or beside shallow waters are
+preferred, but cottonmouths occasionally wander as far as a mile from
+water.
+
+In the pine-oak forests of Nacogdoches County in eastern Texas
+cottonmouths and copperheads are probably the most abundant species of
+snakes. Specimens have been collected near Nacogdoches in ponds, swamps,
+clear and fast-running streams with rock bottoms, and sluggish muddy
+streams. On the Stephen F. Austin Experimental Forest numerous
+cottonmouths live in a swamp until around mid-July, when it becomes dry.
+A small stream west of the swamp seems to be used as a migration route
+to and from the swamp. Slightly more than a mile downstream cottonmouths
+are common in a bottomland area. The ground is always moist and no
+undergrowth occurs; a few small clear springs produce shallow trickles
+that run into a swamp. Cottonmouths can often be found here, lying in or
+beside the small trickles.
+
+I have seen cottonmouths in various types of aquatic habitats in
+Brazoria County. In most places in this area, cottonmouths are found in
+association with one or more species of water-snakes (including _Natrix
+cyclopion_, _N. erythrogaster_, _N. rhombifera_, and _N. confluens_),
+which greatly outnumber the cottonmouth. Interspecific competition may
+be reduced somewhat by cottonmouths sometimes feeding on water-snakes.
+
+The numerous statements in the literature concerning the habitat of the
+cottonmouth can be summarized most easily by the following short
+quotations:
+
+     _Agkistrodon piscivorus piscivorus_--"Marshes and lakes; ponds
+     and streams with wooded shores; low country near water;
+     roadside ponds; drainage ditches; coastal 'banks'; keys; some
+     Gulf coast islands; mangrove swamps." (Wright and Wright,
+     1957:919.)
+
+     _Agkistrodon piscivorus leucostoma_--"Cypress, gum, river
+     swamps; alluvial swamps wooded or not wooded; water courses of
+     the south such as rivers, bayous, backwaters of small branches;
+     hill streams in the north; ... marshy places in prairies ...
+     rice fields, bottomland pools; margins of above habitats,
+     pools, shallow lakes, swampy places, temporary flood lands....
+     In, under, or on fallen timber, in holes in banks, rocky
+     bluffs, crayfish burrows. In short it is very aquatic." (Wright
+     and Wright, _op. cit._:923.)
+
+Geographically cottonmouths differ somewhat in their ecological
+requirements, but are basically much alike in most respects. The areas
+of greatest abundance are those having 40 inches or more of annual
+rainfall. The northern edge of the range has a mean temperature of
+approximately 38° F. in January in Virginia and 30° F. in Missouri,
+although the lowest temperature reached in these areas is more important
+as a limiting factor. The annual rainfall in both Virginia and Missouri
+amounts to approximately 40 inches. Moisture, as well as temperature,
+may play an important role in the northward distribution of the species.
+The eastern cottonmouth seems to be less tolerant of low temperatures
+than the western subspecies. Mean January temperatures equal to those
+along the northern limits of the western cottonmouth's distribution are
+reached in the vicinity of Connecticut, which is north of the geographic
+range of the eastern subspecies.
+
+The depths to which cottonmouths penetrate into their dens may have a
+limiting influence upon the geographic range, especially in the northern
+extremes. Bailey (1948:215) discussed the possibility that populations
+of snakes may be significantly depressed because of winter kill of
+individuals that "hibernate" at shallow depths. He speculated also that
+the short growing season does not allow enough time for the essentials
+of existence to be carried out, and the prolonged period of inactivity
+overtaxes the energy reserve of the species.
+
+Available food does not seem to be of much importance as a limiting
+factor, for the cottonmouth is remarkably indiscriminate in its choice
+of prey, feeding upon almost any vertebrate animal that happens to come
+within reach. Competition for food, however, may play an important role.
+
+
+
+
+REPRODUCTION
+
+Courtship and Mating
+
+
+A review of available literature indicates no records of courtship of
+the cottonmouth other than statements that breeding occurs in early
+spring. In a close relative, the copperhead (see Fitch, 1960:159-160),
+mating occurs almost any time in the season of activity but is mainly
+concentrated in the few weeks after spring emergence, at about the time
+when females are ovulating. Klauber (1956:692) concluded that along the
+southern border of the United States rattlesnakes normally mate in
+spring soon after coming out of their winter retreats; but farther north
+where broods are produced biennially, the mating times may be more
+widely dispersed, and summer and fall matings may even predominate.
+
+The only record of copulation in the cottonmouth was reported by Allen
+and Swindell (1948:11), who observed a pair copulating for three hours
+on October 19, 1946, at the Ross Allen Reptile Institute. Davis
+(1936:267-268) stated that courtship in cottonmouths is violent and
+prolonged but did not note any nervous, jerky motions or nudging of the
+female along her back and sides as had been observed in other genera of
+snakes. Carr (1936:90) saw a male cottonmouth seize a female in his
+mouth and hold her, but no courtship followed.
+
+
+Reproductive Cycles
+
+Many persons have assumed that gestation periods in snakes are the
+intervals between mating and parturition, and that mating and ovulation
+occur at approximately the same time. However, retention of spermatozoa
+and delayed fertilization indicate that copulation is not a stimulus for
+ovulation.
+
+A biennial reproductive cycle was found for the copperhead in Kansas
+(Fitch, 1960:162), the prairie rattler in Wyoming (Rahn, 1942:239) and
+in South Dakota (Klauber, 1956:688), the great basin rattler in Utah
+(Glissmeyer, 1951:24), and the western diamondback rattler in
+northwestern Texas (Tinkle, 1962:309). Klauber's (1956:687) belief that
+the reproductive cycle of rattlesnakes varies with climate, being
+biennial in the north and annual in the south, is supported by similar
+climatic variation in the reproductive cycle of the European viper which
+was discussed by Volsøe (1944:18, 149).
+
+If data for a large number of females were arranged as are those in
+Table 8, they might reveal whether the breeding cycle is annual or
+biennial. The figures presented in Table 8 are misleading if viewed
+separately because of the small number of individuals included in some
+of the size classes.
+
+The smallest reproductive female found measured 455 millimeters in
+snout-vent length. Conant (1933:43) reported that a female raised in
+captivity gave birth to two young at an age of two years and ten months.
+The size classes represented by gravid females found by Barbour
+(1956:38) in Kentucky indicate that breeding occurs at least by the
+third year.
+
+The ovaries of female cottonmouths examined revealed ova in various
+stages of development. In individuals less than 300 millimeters in
+snout-vent length the ovaries are almost completely undeveloped; in
+immature individuals from 300 to 450 millimeters in length the follicles
+are from one to two millimeters in length; in post-post females
+follicles vary in size, the largest being about seven millimeters.
+Reproductive females also contain follicles of various sizes. One or two
+sets are less than three millimeters in length, and large ova that soon
+are to be ovulated are present. Ovarian ova found in April ranged in
+length from 23 to 35 millimeters. No embryonic development was observed
+in most individuals until June or later.
+
+     TABLE 8.--Percentage of Gravid Females of _A. p. leucostoma_ in
+     50 Millimeter Size Classes.
+
+   =====================================
+  |Snout-vent |Number |Total |Percentage|
+  |           |  of   |number|          |
+  |  length   |gravid |  in  |  gravid  |
+  |           |females| size |          |
+  |           |       |class |          |
+  |-----------+-------+------+----------|
+  | 450-499   |   3   |  14  |   21.4   |
+  | 500-549   |   7   |  17  |   41.2   |
+  | 550-599   |   8   |  17  |   47.1   |
+  | 600-649   |   5   |  7   |   71.4   |
+  | 650-699   |   2   |  9   |   22.2   |
+  | 700-749   |   2   |  3   |   66.7   |
+  | 750-799   |   1   |  1   |  100.0   |
+  | 850-899   |   1   |  1   |  100.0   |
+  |  Totals   |  29   |  69  |   42.0   |
+   -------------------------------------
+
+Increase in length of testes appears to be correlated with length of the
+individual rather than cyclic reproductive periods (Fig. 4).
+
+The reproductive cycle in cottonmouths resembles that illustrated by
+Rahn (_op. cit._:237), in which the ovarian follicles of post-partum
+females begin to enlarge in late summer and autumn, with ovulation
+occurring the following spring. By means of retaining sperm successive
+broods possibly are produced after only one mating. In captivity, at
+least, some females may not follow this biennial cycle; Stanley Roth
+(M.S.), biology teacher in high school at Lawrence, Kansas, had a female
+of _A. p. piscivorus_, from Florida, that produced broods of 14 and 12
+young in two consecutive years.
+
+[Illustration: FIG. 4. Length of testes in cottonmouths of various
+sizes (·--left; º--right). The right testis is always longer than
+the left.]
+
+
+Embryonic Development
+
+After ova are fertilized a three and one-half to four-month period of
+development begins which varies somewhat depending on the temperature.
+In almost every instance the ova in the right uterus outnumber those in
+the left. Embryos usually assume the serpentine form in the latter part
+of June and are coiled in a counterclockwise spiral with the head on the
+outside of the coil. At this time the head is relatively large and
+birdlike in appearance with conspicuous protruding eyes. Sex is easily
+noted because the hemipenes of males are everted. By late July scales
+are well developed and the embryo is more snakelike in appearance, but
+pigmentation is still absent. By mid-August the color and pattern are
+well developed, the egg tooth is present, the snake shows a considerable
+increase in size over that of the previous month, and much of the yolk
+has been consumed. Some females that contain well developed embryos also
+contain eggs that fail to develop. Sizes of ova vary irrespective of
+size of female and stage of embryonic development. Lengths of ova ranged
+from 22 to 51 millimeters in May to 35 to 49 millimeters in July and
+August. A two-yolked egg was found in one female.
+
+
+Birth of Young
+
+Accounts in the literature of 15 litters of cottonmouths fix the time of
+birth as August and September. Conant (1933:43) reported the birth of a
+litter in mid-July by a female that had been raised in captivity, and
+one female that I had kept in captivity for two months gave birth to a
+litter between October 19 and October 25. The conditions of captivity
+undoubtedly affected the time of birth in both instances.
+
+Wharton (1960:125-126) reported the birth and behavior of a brood of
+seven cottonmouths in Florida. I was given notes of a similar nature by
+Richard S. Funk of Junction City, Kansas, on a brood of five
+cottonmouths. The mother of the brood was caught in June, 1962, in
+Tarrant County, Texas, by Richard E. Smith, and was 705 millimeters in
+snout-vent length. The first young was found dead in an extended
+position a few inches from the fetal membranes at 11:05 p.m. on August
+22. The second young was born at 11:07 p.m. The intervals between the
+successive births were three, seven, and four minutes; and time until
+the sac was ruptured in each instance was six, five, eight, and 11
+minutes. The time interval between the rupture of the sac and emergence
+of each individual was 41, 92, 154, and 34 minutes. The mother's actions
+in giving birth to the last four young were essentially as described by
+Wharton (_loc. cit._), except that the intervals between successive
+births did not increase. Within one minute after rupturing the sac and
+while its head was protruding, each of the four living young opened its
+mouth widely from three to seven times, then took its first breath.
+Breaths for the first three hours were steady at three or four per
+minute but then decreased to two or three per minute. Pulse rate for the
+four averaged 38 per minute while at rest but increased to 44 per minute
+after voluntarily crawling.
+
+
+Number of Young per Litter
+
+Records of from one to 16 young per litter have been reported (Ditmars,
+1945:330; Clark, 1949:259), but the average is probably between six or
+seven. Most accounts in the literature present information on number of
+ova or embryos per female rather than the number of young. Size and age
+of the mother (Table 9) influence the number of ova produced. Allen and
+Swindell (1948:11) recorded three to 12 embryos in 31 cottonmouths
+varying in total length from 26 to 44 inches. An average of 6.5 embryos
+per female was found.
+
+     TABLE 9.--Number of Ova Produced by Fecund Cottonmouths.
+
+  ====================+============+======================
+    Snout-vent length |  Number    |    Number of ova,
+     in millimeters   | in sample  | average and extremes
+  --------------------+------------+----------------------
+         450-549      |     10     |     4.1 (2 to 7)
+         550-649      |     11     |     4.9 (1 to 8)
+         650-749      |      4     |     6.3 (4 to 8)
+         750-849      |      1     |          5
+         850-949      |      1     |         14
+  --------------------------------------------------------
+
+Mortality at birth has been recorded for almost every litter born in
+captivity (see Allen and Swindell, _loc. cit._; Conant, 1933:43;
+Wharton, 1960:125). A female that I kept in captivity gave birth to
+seven young. Three never ruptured their sacs, and another died soon
+after leaving the sac. The effects of captivity on females may result in
+higher rates of deformity and mortality in young than is common in
+nature. Klauber (1956:699-700) estimated that the defects brought about
+by conditions of captivity on rattlesnakes eliminate about three young
+per litter.
+
+
+Population Composition
+
+No investigator has yet analyzed the composition of a population of
+cottonmouths according to age, sex and snout-vent length. Barbour
+(1956:35) did sort 167 snakes into size classes, but did not determine
+sex ratio, size at sexual maturity, reproductive cycles, or snout-vent
+length. He recorded total lengths from which snout-vent lengths cannot
+be computed because of differential growth rates and different bodily
+proportions of the two sexes. I judge from my findings that he included
+immature individuals in his three smallest size classes (45.5 per cent
+of the population). I found at least 32.5 per cent immature individuals
+(Fig. 5) in my material, but it was not a natural population.
+
+The sex ratios of several small collections from natural populations
+varied, and no conclusions could be drawn. Females comprised 53 per cent
+of the specimens included in Fig. 5 and in a group of 48 embryos which
+represented eight broods. That percentage may not be the percentage in a
+natural population but is used in making assumptions because I lack
+better information.
+
+
+Reproductive Potential
+
+If data in Fig. 5 are representative of a natural population and if 61
+per cent of the females are sexually mature, the reproductive potential
+can be estimated as follows: assuming a cohort of 1000 cottonmouths
+contains 530 females, 61 per cent of the females (323 individuals)
+probably are adults. If 42 per cent of these females produce 6.5 young
+per female in any season (Tables 8 and 9), 136 females will produce 884
+young. But if 50 per cent of the adult females are reproductive (as
+would be assumed if reproduction is biennial), 1050 young will be
+produced. Actually the number of young required per year to sustain a
+population is unknown, because mortality rates at any age are unknown.
+
+[Illustration: FIG. 5. Composition of a group of cottonmouths examined
+in this study. Individuals less than 450 millimeters in snout-vent
+length are considered as immature. Specimens from 200 to 249 millimeters
+in length are included in the 200-millimeter class, _etc._]
+
+
+
+
+GROWTH AND DEVELOPMENT
+
+Size at Birth and Early Growth
+
+
+Size at birth depends on the health of the mother. According to Fitch
+(1960:182), many litters of copperheads born in captivity are stunted.
+Seven young cottonmouths (two males and five females) born in captivity
+were each 185 millimeters in snout-vent length and 40 millimeters in
+tail length. Weights of the three living young were 10.0, 10.1, and 11.1
+grams. Another litter of five young measured by Richard S. Funk were
+larger, and differences in the proportions of the tail length and
+snout-vent length suggest the sexual dimorphism found in larger
+individuals. However, sex of these young snakes was not recorded.
+Snout-vent length and tail length in millimeters were 232, 41; 243, 47;
+229, 40; 240, 48; and 225, 40 in the order of their birth. These snakes
+are considerably smaller than the nine young of _A. p. piscivorus_
+reported by Wharton (1960:127) that averaged 338 millimeters total
+length and 28.7 grams. The yolk of one young _piscivorus_ was 11.7 per
+cent of the total weight. Yolk is used up in about two weeks if its rate
+of utilization resembles that of the copperhead as reported by Gloyd
+(1934:600).
+
+Early rates of growth of three living young are shown in Table 10. On
+the 56th day after birth, each was fed one minnow less than two inches
+long. Between the 80th and 120th days three additional small minnows
+were fed to each snake. Young cottonmouths increase nearly 50
+millimeters in length by the first spring if they inhabit warm areas and
+feed in autumn or winter.
+
+Variation in size of newborn cottonmouths may be less in nature than in
+captivity. Average size at birth can be determined accurately by the
+size of young captured in early spring, at least in northern parts of
+the range where winter feeding and growth do not occur at all or are
+negligible. Total lengths of 19 juveniles thought by Barbour (1956:38)
+to be seven to eight months old do not differ markedly from lengths of
+the five newly-born young measured by Funk.
+
+     TABLE 10.--Rate of Growth of Three Young Cottonmouths.
+
+      ========+=================================================
+     |        |  Snout-vent length/tail length--weight in grams  |
+     |  Age   +----------------+----------------+----------------|
+     |in days |  Female No. 1  |  Female No. 2  |      Male      |
+     |--------+----------------+----------------+----------------|
+     |    2   | 185/40--11.1   | 185/40--10.1   |  185/40--10.0  |
+     |    7   | 192/40--       | 190/40--       |  189/40--      |
+     |   22   | 195/40--10.3   | 200/41.5--10.6 |  197/40--      |
+     |   80   | 204/40--11.7   | 203/42--10.4   |  218/48--14.3  |
+     |   88   |      ....      | 204/44--       |      ....      |
+     |  143   | 215/40.5--13.3 |      ....      |  225/48--15.1  |
+      --------+----------------+----------------+----------------
+
+
+The Umbilical Scar
+
+The umbilical cord is broken at birth and the navel closes within a few
+days; but the scar, involving from two to four ventral scales, remains
+throughout life. Position of the scar was found by Edgren (1951:1) to be
+sexually dimorphic in the eastern hog-nose snake (_Heterodon
+platyrhinos_), but nothing has been published on this matter concerning
+the cottonmouth. Consequently, I counted the scales of several
+individuals from the anal plate, and there was no marked difference in
+the position of the scar in males and females; it varied in position
+from the 10th to the 18th scale. When counted from the anterior end, the
+scar ranged from ventral number 115 to 122 (average, 119) in 28 females
+and from number 117 to 126 (average, 121) in 14 males. The difference
+between male and female cottonmouths is not nearly so great as in
+_Heterodon_.
+
+
+Later Growth and Bodily Proportions
+
+The only records of growth increments in a natural population of
+cottonmouths are those in Table 11. The period of growth is mostly the
+period of activity, and differences are expected between northern and
+southern populations. As size increases, determination of growth rate
+becomes more difficult because age classes overlap in size. Growth of
+any individual depends not only on climate and food but also on disease
+and parasitism and the innate size potential. Stabler (1951:91) showed
+weight and length relationships in two cottonmouths for a period of six
+and one-half years.
+
+     TABLE 11.--Growth Increments in Cottonmouths (Barbour,
+     1956:38-39).
+
+   =============================================
+  | Number of |   Total   |Estimated| Estimated |
+  |           |  length   |   age   |  growth   |
+  |           |           |         |   from    |
+  |           |           |         | preceding |
+  |           |           |         |   year    |
+  |individuals|    in     |in months|    in     |
+  |           |millimeters|         |millimeters|
+  |-----------+-----------+---------+-----------|
+  |    19     |  260-298  |   7-8   |    25     |
+  |    11     |  312-337  |  19-20  |    45     |
+  |    40     |  355-485  |  31-32  |    95±    |
+  |    83     |  500-1000 |  43-44+ |     ?     |
+   ---------------------------------------------
+
+My study failed to reveal any secondary sexual difference in growth rate
+and maximum size. Of the 306 cottonmouths measured by me, 16 males and
+five females exceeded 700 millimeters in snout-vent length. Two males
+were more than 850 millimeters long. One cottonmouth lived in captivity
+for 18 years and 11 months (Perkins, 1955:262). The maximum total
+lengths were reported by Conant (1958:186-187) to be 74 inches (1876
+mm.) in _A. p. piscivorus_ and 54 inches (1370 mm.) in _A. p.
+leucostoma_.
+
+[Illustration: FIG. 6. Head length (º) and head width (·) expressed as a
+percentage of snout-vent length of living and preserved cottonmouths.
+Head length was measured from the tip of the snout to the posterior end
+of the mandible. Head width was measured across the supraocular scales,
+since accuracy was greater than if measured at the posterior edge of the
+jaw. No sexual dimorphism or geographical variation occurs in these
+characters.]
+
+Proportions of various parts of the body vary considerably depending on
+age, size and, in some instances, sex. Heads are proportionately larger
+in young than in adults (Fig. 6), as is true of vertebrates in general.
+This larger head has survival value for the cottonmouth in permitting
+more venom to be produced and in permitting it to be injected deeper
+than would be the case if the proportions were the same as in adults.
+Relative to the remainder of the snake the head is considerably larger
+than in the copperhead (Fitch, 1960:108) and slightly larger than in the
+rattlesnake, _Crotalus ruber_ (Klauber, 1956:152).
+
+[Illustration: FIG. 7. Tail length expressed as a percentage of
+snout-vent length of living and preserved cottonmouths (·--males;
+º--females).]
+
+In general, tails are relatively longer in males than in females of the
+same size (Fig. 7), except that there is little or no difference at
+birth. Growth of the tail in males proceeds at a more rapid rate. In
+certain individuals sex cannot be recognized from length of the tail
+relative to snout-vent length because overlapping occurs, especially in
+medium-sized individuals. Similar changes of proportions with increase
+in age occur in copperheads (Fitch, 1960:106) and rattlesnakes (Klauber,
+1956:158-159), but the tail of the cottonmouth is relatively much
+longer.
+
+
+
+
+SHEDDING
+
+The Shedding Operation
+
+
+Shedding of the skin is necessary to provide for growth and wear in
+snakes. The milkiness or bluing of the eyes, which causes partial
+blindness, marks the initial stage of shedding and is caused by a
+discharge of the exuvial glands that loosens the old _stratum corneum_
+from the layer below. In four to seven days the opaqueness disappears,
+and the snake sheds after an additional three to six days (Table 12).
+Young snakes first shed within a few days after birth and generally shed
+more frequently than adults, but the interval is variable. The eyes of
+three young cottonmouths observed by Wharton (1960:126) became milky on
+the fourth day but cleared on the seventh day, and the skin was shed on
+the eighth day. The eyes of three young kept by me became milky two to
+three days after birth, cleared on the seventh to tenth days, and the
+skin was shed on the thirteenth day. Possibly the relatively long
+interval in this instance resulted from low relative humidity in the
+room where the snakes were kept. According to Fitch (1960:134), litters
+of young copperheads usually shed within three to ten days after birth;
+but under unusually dry conditions shedding did not occur for several
+weeks.
+
+     TABLE 12.--Duration of Preparatory Period (in days) to Shedding
+     in 11 Cottonmouths.
+
+   ==============================
+  |Duration  |  Time  |Time from |
+  |   of     |between |beginning |
+  |cloudiness|clearing|    of    |
+  |          |  and   |cloudiness|
+  |of eyes   |shedding|  until   |
+  |          |        | shedding |
+  |----------+--------+----------|
+  |    5     |   6    |    11    |
+  |    7     |   3    |    10    |
+  |    -     |   -    |     6    |
+  |    -     |   -    |     6    |
+  |    5     |   3    |     8    |
+  |    4     |   6    |    10    |
+  |    7     |   3    |    10    |
+  |    5     |   6    |    11    |
+  |    5     |   3    |     8    |
+  |    7     |   -    |    -     |
+  |    7     |   3    |    10    |
+  |   ----   |    ----|     ---- |
+  |[=X] 5.4  |[=X] 3.8| [=X] 9.0 |
+   ------------------------------
+
+Cottonmouths as well as other snakes usually do not feed until after the
+skin is shed and are generally quiescent during the period preceding
+shedding, except that immediately before shedding they become active and
+rub their snouts on some rough object and may yawn several times
+seemingly in an attempt to loosen the skin along the edges of the lips.
+After the skin is loosened from the head, more rubbing against rough
+surfaces and writhing serves to pull the old skin off, turning it inside
+out. Once the old skin has passed over the thick mid-body, the snake
+often crawls forward using rectilinear locomotion until the skin is
+completely shed. It normally comes off in one piece; but, if the snake
+is unhealthy or has not had sufficient food or water, the skin may come
+off in patches. Frequently one or both of the lens coverings are not
+shed immediately and impair the sight. Bathing or swimming ordinarily
+causes dried skin to peel off; and, because of the cottonmouth's aquatic
+habits, its chances of shedding successfully are much greater than those
+of less aquatic snakes. Cottonmouths that have recently shed have bright
+and glossy patterns, in contrast to the dull and dark appearance of
+those that are preparing to shed.
+
+
+Frequency of Shedding
+
+Most of our knowledge concerning the frequency of shedding is based upon
+observations of captives. It is known that the intervals between
+exuviations are largely dependent upon the amount of food taken and the
+rate of growth. Unless laboratory conditions closely resemble those in
+the field, shedding frequencies in captives probably differ much from
+those of free-living snakes.
+
+Only two of my captives shed twice. The intervals between exuviations in
+the two snakes were eight and five months, lasting from August to April
+and from December to May, respectively. Ten other snakes shed once in
+the period from January through July. Stabler (1951:91) presented data
+concerning shedding of two cottonmouths kept 12 and 14 years in
+captivity. One shed 25 times in 12 years and the other shed 37 times in
+14 years, giving an average of 2.1 and 2.6 per year, respectively.
+Neither of the snakes shed from December through March, but the period
+of shedding corresponded to the period of greatest activity and growth.
+In Florida, cottonmouths shed four to six times a year, according to
+rate of growth (Allen and Swindell, 1948:7).
+
+
+
+
+FOOD HABITS
+
+Methods of Obtaining Prey
+
+
+Food is obtained by a variety of methods depending on the type of food,
+age of the cottonmouth, and possibly other factors. Some captives lie in
+ambush and others crawl slowly in active search. At the first cue of
+possible prey, either by sight, scent, or differential temperature
+detection by the pit, the snake appears to become alert and flicks its
+tongue out at fairly rapid intervals.
+
+By means of the facial or loreal pit found in all crotalids, the snake
+is able to detect objects having temperatures different from that of the
+surroundings of the objects. In detecting prey the tongue acts to
+sharpen the sense of "smell" by conveying particles to Jacobson's organs
+in the roof of the mouth. On many occasions cottonmouths appeared to
+rely solely on sight; they passed within a few inches of prey,
+apparently unaware of its presence until it moved. When pools of water
+begin to dry up toward the end of summer, cottonmouths often congregate
+and feed on dying fish. In these instances the fish are usually taken as
+they come to the surface. In laboratory observations moccasins seize
+live fish and some moccasins carry the fish until they have received
+lethal doses of venom; afterward the fish are swallowed. But grasping
+and manipulation of the prey occurs without the fangs' being employed,
+especially in the case of dead fish. On one occasion a cottonmouth was
+observed to grasp the edge of a glass dish that had contained fish and
+apparently retained the odor. On another occasion I placed several fish
+in a bowl, rubbed a stick on the fish, and then touched each snake
+lightly on the nose with the stick. The snakes crawled directly to the
+bowl and began feeding. At other times these same snakes crawled around
+the cage in an apparent attempt to locate the food but paid little
+attention to fish held in front of them. If the catching of prey under
+natural conditions were as uncoordinated as it sometimes is in
+captivity, the snakes probably would not be able to survive.
+
+Wharton (1960:127-129) described tail-luring in one individual of a
+76-day-old brood of cottonmouths. The snake lay loosely coiled with the
+tail held about six centimeters from the ground; a constant waving
+motion passed posteriorly through the terminal inch of the tail. These
+movements ceased at 7:20 p.m. but were resumed at 7:40 a.m. the
+following day. All observations were under artificial light. The "caudal
+lure" as a means of obtaining prey has been described in other species
+and related genera by Neill (1960:194) and Ditmars (1915:424).
+
+Various authors have suggested that the method of capture differs
+according to the kind of prey. Allen and Swindell (1948:5) stated that
+cottonmouths retain their hold after striking fish or frogs but will
+release a mouse after delivering a bite and are timid in striking at
+larger rodents. Neill (1947:203) noted that a cottonmouth always waited
+several minutes after biting a large rat before approaching its prey.
+This same type of behavior has been reported for copperheads (Fitch,
+1960:194) and rattlesnakes (Klauber, 1956:618). Cottonmouths observed by
+me retained a strong hold on fish, frogs, and sometimes mice, but almost
+always released large mice and baby chicks, which were not eaten until
+after death.
+
+Different behavior according to type of prey is correlated with ability
+of prey to retaliate, although some animals may not be released because
+they could easily escape. For instance, a frog could hop far enough to
+escape in a matter of seconds if released. A 73-millimeter _Rana
+pipiens_ that I observed was bitten twice within one and a quarter hours
+and died 45 minutes after the last bite. Its movement was uncoordinated
+by the time of the second bite, but it could have escaped had the frog
+not been confined. Although it is doubtful that normal, healthy fish are
+frequently captured by cottonmouths, Allen (1932:17) reported that a
+cottonmouth was seen pushing a small, dead pike about on the surface of
+a stream. A wound on the belly of the fish indicated that it had been
+bitten. A 17-gram creek chub (_Semotilus_) and a 13.7-gram bass
+(_Micropterus_) were injected by me with one-fourth cubic centimeter of
+fresh venom near the base of the tail in order to determine whether the
+fish could escape after being bitten and released. The creek chub
+flipped onto its back after a minute and 45 seconds and gill movements
+stopped in eight minutes and 35 seconds; the bass flipped over after 50
+seconds and died in two minutes and 10 seconds. The venom immediately
+affected both fish, and it is unlikely that either could have swum more
+than a few feet.
+
+After its prey has been killed, a cottonmouth examines the body from end
+to end by touching it with the tongue. Then the animal is grasped in the
+mouth without the use of the fangs and is slowly manipulated until one
+end (usually the head) is held in the mouth. The lengthy process of
+swallowing then takes place, the fangs and lower jaws alternately
+pushing the prey down the throat.
+
+
+Food and Food Preferences
+
+The cottonmouth seems to be an opportunistic omni-carnivore, because it
+eats almost any type of flesh that is available, including carrion. It
+feeds primarily upon vertebrates found in or near water; but
+invertebrates and eggs have also been found in the diet. The only
+potential prey items that seem not to be normally eaten are bufonid
+toads and tadpoles. I have occasionally offered tadpoles and frogs to
+cottonmouths, but only the frogs were accepted. But, Stanley Roth kept a
+cottonmouth in captivity that ate both toads and tadpoles. If tadpoles
+are commonly eaten, their probable rapid digestion would make
+identification almost impossible.
+
+Following is a list of known foods of the cottonmouth:
+
+     Captivity: "... rattlesnake.... The same moccasin also killed
+     and ate a smaller snake of its own species...." (Conant,
+     1934:382.)
+
+     Florida: "3 heron feathers, bird bone, _Eumeces inexpectatus_,
+     3 fish all under one inch in length, 1 heron egg shell" (Carr,
+     1936:89). According to Allen and Swindell (1948:5), "the food
+     included other moccasins, prairie rattlesnakes, king-snakes,
+     black snakes, water snakes, garter snakes, ribbon snakes, and
+     horn snakes ... most of the species of frogs, baby alligators,
+     mice, rats, guinea pigs, young rabbits, birds, bats, squirrels,
+     and lizards ... a mud turtle ... a case of a four footer eating
+     ten to twelve chicken eggs. The most common food appears to be
+     fish and frogs. Catfish are included on this list...." Yerger
+     (1953:115) mentions "an adult yellow bullhead, _Ameiurus
+     natalis_ ... 306 mm. in standard length [from a 63-inch
+     cottonmouth]."
+
+     Georgia: "... full grown _Rana catesbeiana_, several foot-long
+     pickerel ... dead fish if placed in a pan of water.... _Natrix
+     sipedon fasciata_ and _Masticophis flagellum_ ... rats....
+     Toads and large _Eumeces laticeps_ were always ignored."
+     (Neill, 1947:203.) "_Natrix_, _Heterodon_, _Kinosternon_,
+     _Rana_, _Hyla cinerea_, _Microhyla_, Microtine [_Pitymys
+     pinetorum_]." (Hamilton and Pollack, 1955:3.)
+
+     Mississippi: "... _Hyla gratiosa_.... In captivity specimens
+     have eaten frogs, mice, birds, dead fish, pigmy rattlers and
+     copperheads. Toads ... were refused" (Allen, 1932:17). One
+     moccasin "disgorged a smaller decapitated moccasin ... killed
+     the day before by boys" (Smith and List, 1955:123).
+
+     Tennessee: "Beetles in one stomach; lizard (_Eumeces_) in
+     another stomach; small snake (_Natrix_) in one intestine, and
+     hair in another intestine. One stomach contained numerous bits
+     of wood, up to four inches in length...." (Goodman, 1958:149.)
+
+     Kentucky: "_Siren intermedia_ was the most abundant food item
+     in both volume and occurrence. Frogs of the genus _Rana_ ranked
+     second. Together, these two items comprised almost 2/3 of the
+     food of the snakes. The other food items were distributed among
+     the fishes, reptiles, and other amphibians [one _Rana_ tadpole
+     included]." (Based on 42 samples--Barbour, 1956:37.)
+
+     Illinois: (Based on 84 samples--Klimstra, 1959:5.)
+
+                          _Per cent Frequency_    _Per cent_
+     _Food Item_            _of Occurrence_        _Volume_
+
+     Pisces                      39.3                31.9
+     Amphibia                    36.9                26.0
+     Reptilia                    25.0                18.2
+     Mammalia                    30.9                17.9
+     Gastropoda                  17.8                 1.0
+     Miscellaneous               25.0                 5.0
+       (Algae, Arachnida,
+       Aves, Insecta)
+
+     Louisiana: Penn (1943:59) mentions that a "female had just
+     eaten two young cottonmouths...." Clark (1949:259) mentions
+     "100 specimens--34 fish; 25 _Rana pipiens_; 16 _Rana
+     clamitans_; 7 _Acris_; 4 _Natrix sipedon confluens_; 8 birds; 5
+     squirrels ... catfish thirteen and one-half inches in length
+     ... small-mouth black bass [eleven inches]."
+
+     Oklahoma: Force (1930:37) remarks that the moccasin "eats
+     bullfrogs ... but refuses leopard frogs." Trowbridge (1937:299)
+     writes: "several sun perch.... Another had eaten six catfish
+     six to ten inches long ... a water snake (_Natrix s.
+     transversa_) about 18 inches long ... frogs, mostly _Rana
+     sphenocephala_." Carpenter (1958:115) mentions "a juvenile
+     woodthrush.... Seven last instar cicadas ... a young
+     cottontail." According to Laughlin (1959:84), one moccasin
+     "contained the following items: 18 contour feathers of a duck,
+     probably a teal; one juvenile cooter turtle, _Pseudemys
+     floridana_; and a large mass of odd-looking unidentifiable
+     material. The other cottonmouth contained one juvenile pond
+     turtle, _Pseudemys scripta_...."
+
+     Texas: "... several ... feeding on frogs.... One ... found DOR
+     was found to contain a large catfish." (Guidry, 1953:54.)
+
+Of 246 cottonmouths that I examined for food items, only 46 contained
+prey in their digestive tracts. Almost all of the snakes examined were
+museum specimens that had been collected at many places over a period of
+about 40 years. It was not known how long each had been kept alive
+before being preserved. Therefore it was impossible to determine what
+proportion of any population of cottonmouths could be expected to
+contain food. The food items were not analyzed numerically because the
+scales and hair, by means of which many food items in the intestine were
+identified, yielded no clue as to the number of individuals actually
+present unless several distinct kinds were found. Each occurrence of
+scales or hair was thus recorded as a single individual, although some
+such occurrences may have represented more than one animal. The contents
+of some stomachs were so well digested that it was difficult to
+determine the number of items present. As a rule only one food item was
+present in a digestive tract, but a few tracts contained several items
+of the same or different species. Three frogs (_Acris crepitans_) were
+in one snake and three hylas (_Hyla versicolor_) in another. Still
+another individual captured beside a drying pond contained six
+individuals of _Lepomis_ each about three inches long and two pikes
+(_Esox_) about six inches long.
+
+    TABLE 13.--Analysis of Food Items of 46 Cottonmouths Collected
+    in Arkansas, Louisiana, and Texas (1922-1962).
+
+   ===========================+========+==========+=========+==========
+  |                           | Number | Percent  |Estimated|Estimated |
+  |                           |   of   |          |         |          |
+  |                           |samples |frequency | weight  |percentage|
+  |                           |   in   |          |         |          |
+  |        FOOD ITEMS         | which  |    of    |   in    |    by    |
+  |                           |  item  |          |         |          |
+  |                           |occurred|occurrence|  grams  |   bulk   |
+  |---------------------------+--------+----------+---------+----------|
+  |Fish                       |  (7)   |   13.2   |   20    |   18.4   |
+  |  _Esox_ sp.               |   1    |          |         |          |
+  |  _Lepomis_ sp.            |   2    |          |   15    |          |
+  |  Unidentified             |   4    |          |         |          |
+  |Amphibians                 |  (12)  |   23.0   |         |   20.4   |
+  |  _Scaphiopus hurteri_     |   1    |          |   13    |          |
+  |  _Acris crepitans_        |   2    |          |    4    |          |
+  |  _Hyla cinerea_           |   2    |          |   12    |          |
+  |  _Hyla versicolor_        |   1    |          |   12    |          |
+  |  _Rana catesbeiana_       |   1    |          |   20    |          |
+  |  _Rana pipiens_           |   3    |          |   15    |          |
+  |  Unidentified             |   2    |          |         |          |
+  |Reptiles                   |  (15)  |   28.4   |         |   29.9   |
+  |  _Pseudemys scripta_      |   2    |          |   15    |          |
+  |  _Anolis carolinensis_    |   1    |          |    6    |          |
+  |  _Eumeces fasciatus_      |   1    |          |    7    |          |
+  |  _Lygosoma laterale_      |   2    |          |    5    |          |
+  |  _Natrix_ sp.             |   1    |          |   10    |          |
+  |  _Natrix erythrogaster_   |   2    |          |   10    |          |
+  |  _Agkistrodon piscivorus_ |   2    |          |   20    |          |
+  |  _Crotalus_ sp.           |   1    |          |   30    |          |
+  |  Unidentified snakes      |   3    |          |         |          |
+  |Birds                      |  (4)   |   7.6    |         |   18.6   |
+  |  _Anhinga anhinga_ (juv.) |   1    |          |   60    |          |
+  |  Egret (head and neck)    |   1    |          |   20    |          |
+  |  Passeriformes            |   2    |          |   20    |          |
+  |Mammals                    |  (6)   |   11.3   |         |   12.7   |
+  |  _Blarina brevicauda_     |   1    |          |   12    |          |
+  |  Cricetinae               |   5    |          |   18    |          |
+  |Unidentified               |  (9)   |   17.0   |         |          |
+   ---------------------------+--------+----------+---------+-----------
+
+The "unidentified" category (Table 13) refers to jellylike masses in the
+stomach or material in the intestine in which no scales, feathers, hair,
+or bones could be found. Most of the unidentifiable matter could be
+assumed to consist of remains of amphibians, since they leave no hard
+parts. If this assumption is correct, amphibians comprise about 40 per
+cent of the diet. Since intestinal contents were included, a volumetric
+analysis was not feasible. Therefore, the weight of each type of food
+item was estimated and the percentage by bulk calculated from it (Table
+13).
+
+Pieces of dead leaves and small sticks constituted most of the plant
+material found and presumably were ingested secondarily because they
+adhered to the moist skin of the prey, especially to fish and
+amphibians. However, some plant materials probably are eaten because
+they have acquired the odor of the prey. One cottonmouth contained a
+_Hyla cinerea_, several leaves, and five sticks from 37 to 95
+millimeters long and from 12 to 14 millimeters in diameter.
+
+Most reports in the literature state that gravid females do not feed,
+but four gravid females examined by me containing large, well-developed
+embryos also contained evidences of having recently fed. Two of them had
+scales of snakes in the stomach or intestine, one contained a six-inch
+_Lepomis_, and the other had hair in the intestine and the head and neck
+of an adult egret in the stomach.
+
+
+
+
+MORTALITY FACTORS
+
+Natural Enemies and Predators
+
+
+Published records of other animals preying on cottonmouths or killing
+them are few. Reptiles more often than other classes of vertebrates prey
+on the cottonmouth. McIlhenny (1935:44) reported on the scarcity of
+snakes in areas where alligators were present. Predation on cottonmouths
+by indigo snakes (_Drymarchon corais_) was reported by Conant (1958:153)
+and Lee (1964:32). Allen and Swindell (1948:6) obtained a photograph of
+a king-snake (_Lampropeltis getulus_) killing a cottonmouth but thought
+that moccasins are not eaten by _L. getulus_. However, one occasion
+reported herein shows that cottonmouths are eaten by king-snakes; and
+Clark (1949:252) reported finding 13 cottonmouths, along with other
+prey, in the stomach contents of 301 king-snakes (_L. g. holbrooki_)
+from northwestern Louisiana. Cannibalism is also common among
+cottonmouths. Klauber (1956:1058;1079) cited predation on cottonmouths
+by a blue heron (_Ardea herodias_) and a largemouth bass (_Micropterus
+salmoides_). Man is probably the greatest enemy of the cottonmouth.
+Intentional killing, capturing, road kills, and alteration of the
+environment destroy large numbers.
+
+
+Parasites and Diseases
+
+Allen and Swindell (1948:12) listed several diseases and parasites of
+snakes and stated that "some moccasins captured in the woods are so poor
+and weak from parasitic infection that they can barely crawl." The only
+kind of ectoparasite found on captive cottonmouths in the course of my
+study was a snake mite, _Ophionyssus natricus_. An infestation of that
+mite was thought to be partly responsible for the death of one captive
+moccasin. Other moccasins spent increasing amounts of time in their
+water dish after they became infected with mites. Under natural
+conditions frequent swimming probably keeps cottonmouths nearly free of
+mites.
+
+Endoparasites found included lung flukes, stomach nematodes, and
+tapeworms. Lung flukes (_Ochetosoma_ sp.) were found in 16 of 20 captive
+cottonmouths. Snails and frogs serve as intermediate hosts for various
+stages in the life cycle of these flukes. The high percentage of
+cottonmouths infested with flukes is indicative of the use of frogs as a
+major source of food. Less than ten flukes were usually observed in the
+snakes' mouths but occasionally more were seen. One snake was observed
+thrashing about in its cage for nearly an hour, after which time it
+died. Upon examination of the mouth, 32 flukes were found, most of which
+were located in the Jacobson's organs. Whether or not flukes caused the
+death is not known. Nematodes (_Kalicephalus_ sp.) were found in the
+stomach of each of several preserved specimens; most of these snakes had
+no food in their digestive tracts. In a high percentage of the
+moccasins, tapeworms (_Ophiotaenia_ sp.) were in the duodenum, in many
+instances so tightly packed as seemingly to prevent passage of food. The
+importance of fish in the diet is reflected by the high percentage of
+snakes containing tapeworms. An unidentified cyst (?) about an inch long
+and containing two hooks on one end was found attached to the outer wall
+of the stomach of a cottonmouth. Yamaguti (1958) listed all the kinds of
+helminths known from cottonmouths.
+
+
+Miscellaneous Causes of Death
+
+Munro (1949:71-72) reported on the lethal effect of 10 per cent DDT
+powder on two young cottonmouths which were dusted with it to kill
+mites. Herald (1949:117) reported an equal effect caused by spraying a
+five per cent DDT solution in a room with several snakes. All but three
+large cottonmouths, which were under shelter at the time of spraying,
+were killed.
+
+One individual that refused to eat was dissected soon after death, and a
+short piece of a branch on which two large thorns were located at 90°
+angles was found blocking the intestine at the posterior end of the
+stomach.
+
+An unexpected and probably unusual circumstance caused the death of two
+captives. After cleaning a cage containing five cottonmouths and placing
+several mice in the cage for food, I noticed two of the snakes lying
+stretched out, partially on one side, and almost unable to move. At
+first I thought they had been bitten by other snakes which were in
+pursuit of the mice. The two died after two days. When a similar
+incident occurred in another cage, I removed the "bitten" snake and it
+fully recovered after 11 days. When the same symptoms were observed in a
+garter snake in another cage, I realized that in each instance the cage
+had been cleaned and fresh cedar chips placed in it immediately prior to
+observation of these symptoms. Fine cedar dust on the chips had
+evidently poisoned the snakes.
+
+
+
+
+BEHAVIOR
+
+Annual and Diel Cycles of Activity
+
+
+In the days following emergence in spring, cottonmouths often endure
+uncomfortable and even dangerous temperatures in order to obtain food
+and mates. They are more sluggish at this time and more vulnerable to
+predation than later in the season when temperatures are optimal. Fitch
+(1956:463) found that copperheads in northeastern Kansas begin their
+annual cycle of activity in the latter part of April, when the daily
+maximum temperature is about 22° C. and the minimum is about 4° C., and
+become dormant in late October or early November, at which time the
+daily maximum temperature is about 15° and the minimum is about 0°.
+Indications are that in the northern part of its range the annual
+activity cycle of the cottonmouth resembles that of the copperhead in
+northeastern Kansas. Klimstra (1959:2) captured cottonmouths from April
+to October in southern Illinois. Barbour (1956:36) collected large
+numbers of them in early April in Kentucky and stated that they migrate
+from swamps to wooded hillsides in late August and early September.
+Spring migrations begin after a few consecutive warm days in March. In
+northern Oklahoma cottonmouths have been found along the Verdigris River
+as early as March, suggesting that a few winter in crayfish holes and
+mammal burrows. The majority of individuals found in this area were at
+denning sites along cliffs above the river and emerged later than those
+near the river (Dundee and Burger, 1948:1-2). In Virginia cottonmouths
+have been seen as early as March 5 (Martin and Wood, 1955:237) and as
+late as December 4. They have been observed in migration from the swamps
+of the barrier beach to the mainland in late October and early November
+in southeastern Virginia (Wood, 1954a:159). According to Neill
+(1947:204), the cottonmouth tolerates lower temperatures than do most
+snakes in Georgia and is one of the last to go into hibernation. Allen
+and Swindell (1948:4) stated that cottonmouths usually bask during the
+mornings of the cooler months in Florida, but they mentioned nothing of
+denning such as occurs farther north. Although winter aggregations occur
+in the northern parts of the range, I have never seen such aggregations
+in the South. However, in one instance related to me by a reliable
+observer, seven cottonmouths were found together on a creek bank near
+the Gulf Coast in early spring.
+
+During late summer and early autumn, fat is deposited in lobes in the
+lower abdomen in preparation for the period of winter quiescence. Gravid
+females usually do not feed so frequently or so much as other snakes,
+because they tend to become inactive as the ova develop. Whether or not
+females feed heavily after parturition and previous to denning is not
+known. Peaks of activity in autumn may be caused by final attempts to
+feed before denning and by the appearance of large numbers of newborn
+young. The young usually have from one to two months in which to feed
+before the advent of cold weather. According to Barbour's (_op.
+cit._:38) findings, the young probably feed before hibernation because
+they grow substantially in winter. For those that do not feed, the rate
+of survival is perhaps much lower.
+
+In preparation for winter, cottonmouths migrate inland, usually to dry
+forested hillsides where they den, commonly among rocks at the tops of
+bluffs, along with several other species of snakes. In such aggregations
+there is no hostility and each individual may derive benefit from
+contact with others by which favorable conditions of temperature and
+humidity are maintained.
+
+Neill (1947:204) has found many specimens in winter by tearing bark from
+rotting pine stumps on hillsides overlooking lakes or streams. On cold
+days they evidently retreat below the surface, while on warm days they
+lie just below the bark or emerge and bask. Neill believes that the use
+of stumps by cottonmouths is an innate pattern of behavior, because of
+the large number of young-of-the-year found in such surroundings.
+Cottonmouths were observed in winter also under logs and stumps by Allen
+(1932:17). I have twice observed cottonmouths crawling into crayfish
+burrows along the Gulf Coast of Texas, and suppose they are used as
+denning sites to some extent.
+
+The diel cycle of activity of cottonmouths is of necessity closely
+related to the seasonal cycle. Since optimal temperatures determine
+activity, the diel cycle varies greatly from time to time. It has been
+well established that cottonmouths, like most other crotalids and many
+snakes of other families, prefer nocturnal to diurnal activity, even
+though the temperature may be less favorable at night. This preference
+is correlated with increased nocturnal activity of frogs and reptiles
+that constitute the principal food supply.
+
+During spring and autumn, activity is more restricted to the day and
+long periods of basking occur. However, as hot weather approaches,
+basking occurs mainly in the morning and evening and activity becomes
+primarily nocturnal. But, in well shaded, moist forests, cottonmouths
+feed actively in the daytime.
+
+Availability of food also has an important influence upon activity.
+Allen and Swindell (_op. cit._:5) stated that moccasins congregate
+around drying ponds and feed on dying fish until the moccasins can hold
+no more. They then usually stay nearby as long as food remains. In an
+area of the Stephen F. Austin Experimental Forest near Nacogdoches,
+Texas, many cottonmouths journey daily to and from a swamp and a dry
+field, evidently to feed on rodents inhabiting the area. Ten individuals
+captured along a snake-proof fence that was built 30 yards from the
+swamp were found lying coiled along the fence after 4:30 p.m., at which
+time the area was shaded. On another occasion, I captured a large
+cottonmouth that was feeding upon dying fish in a drying pool about
+10:30 a.m. on August 19, 1962.
+
+Because of the aquatic habits of the cottonmouth, relative humidity
+probably has little influence on the snake's activity. However,
+cottonmouths are more restricted to the vicinity of water in dry weather
+than during rains or muggy weather when many of their natural prey
+species also move about more freely. Increased activity on cloudy days
+may result from protection from long exposure to sunshine. Torrential
+rains and floods, such as those following hurricanes along the Gulf and
+Atlantic coasts of the southeastern United States, bring out quantities
+of snakes of all species. Rattlesnakes and cottonmouths in particular
+are killed by the thousands at these times because they seek shelter in
+human habitations. However, these are unusual circumstances and do not
+reflect voluntary activity as a result of preferences.
+
+Thermal reactions of reptiles were classified by Cowles and Bogert
+(1944) into several categories. For each species there is a basking and
+normal activity range limited by the voluntary minimum and voluntary
+maximum at which the animal seeks shelter. Beyond this normal range are
+the critical thermal minimum and critical thermal maximum (C. T. M.) at
+which effective locomotion is prevented. The lethal minimum and maximum
+are those temperatures at which short exposure produces irreparable
+damage, and death inevitably results. These classifications are modified
+somewhat by seasonal or laboratory acclimation or by the physiological
+state of the animal. The C. T. M. of five cottonmouths was determined by
+placing each individual in an enclosed area and heating it with an
+infrared lamp. Cloacal temperatures were taken with a Schultheis
+quick-recording thermometer as soon as the snake could no longer right
+itself when placed on its back. All temperatures were in degrees
+Celcius. The C. T. M. averaged 39.2° (38.0° to 40.0°). A temperature of
+38.0° was lethal to one individual. These cottonmouths had been in
+captivity for nine months. The behavior of the snakes during heating
+resembled those instances described by Klauber (1956:382-387) for
+rattlesnakes. As the body temperature of the snakes rose past the
+optimum, each individual became disturbed and tried to escape from the
+enclosure. The snakes soon became frantic in their efforts to escape.
+After about five minutes the mouth was opened and heavy, slow breathing
+was begun, accompanied by a loss of coordination and a slowing down of
+movements. The snakes writhed spasmodically for a few seconds and then
+lay still, usually with the mouth open. Recovery was begun by rolling on
+the belly and flicking the tongue, followed by movements of the head and
+then the body. Cottonmouths are rarely exposed to dangerously high
+temperatures owing to their semi-aquatic habits, but there are probably
+occasions when individuals reach the C. T. M. for the species.
+
+
+Basking
+
+Since activity, digestion, and gestation depend upon adequate internal
+temperatures, there must be a process by which these temperatures are
+attained and for an appropriate time maintained. Basking is important in
+this respect. The cottonmouths prefer to lie in a coiled position and,
+during basking, can usually be found beside bodies of water or on
+branches of dead trees overhanging the water. They are good climbers and
+have a prehensile tail that is frequently employed in descending from
+small branches. Since cottonmouths are semi-aquatic and are often
+exposed to temperatures that are lower than those of the air, they
+either must bask more often than terrestrial snakes or tolerate lower
+temperatures. Length of the period of basking is determined not only by
+amounts of insolation and temperature but also by the size of the snake.
+A smaller snake can reach its optimum temperature more rapidly because
+of a higher surface-to-volume ratio. Another factor that may play a
+minor role in the rate of temperature change is the color of the snake.
+The wide variation in color of cottonmouths probably affects rates of
+heat increase and loss due to direct radiation. Slight hormonal control
+of melanophores described in snakes by Neill and Allen (1955) also may
+exert some influence on the length of time spent basking. No rates of
+temperature increase or decrease are available for cottonmouths.
+
+
+Coiling
+
+While inactive the cottonmouth spends most of its time lying in a coiled
+position with the tail outermost, with the body usually wound into about
+one and one-half cycles, and the head and neck in a reversed direction
+forming a U- or S-shaped loop. From this position the snake is able to
+make a short strike or a hasty getaway if necessary. In my opinion this
+position is used primarily for basking or resting and only secondarily
+for feeding. Most individuals appear to pursue their prey actively, not
+lying in ambush for the approaching prey to the extent that most other
+crotalids do.
+
+Many of the cottonmouths that I kept in captivity were observed in a
+coiled position for periods up to three or four days. Under natural
+conditions, however, they are more active. Young cottonmouths are
+inclined to remain in a coiled position for longer periods than older
+individuals.
+
+
+Locomotion
+
+Four distinct types of locomotion have been described in snakes:
+horizontal undulatory, rectilinear, sidewinding, and concertina
+(Klauber, 1956: 331-350). Most snakes are capable of employing two or
+more of these types of progression, at least to a certain degree; but
+horizontal undulatory locomotion is the most common method used by the
+majority of snakes, including the cottonmouth. In this method the
+snake's body is thrown into lateral undulations that conform with
+irregularities in the substrate. Pressure is exerted on the outside and
+posterior surface of each curve, thus forcing the body forward.
+
+Rectilinear locomotion is more useful to large, thick-bodied snakes
+which use this method of progression, chiefly when they are prowling and
+unhurried. This method depends upon the movement of alternate sections
+of the venter forward and drawing the body over the ventral scales
+resting on the substratum by means of muscular action. This mode of
+locomotion was most frequently observed in captive cottonmouths when
+they were crawling along the edge of their cages, especially when they
+were first introduced to the cages and toward the end of the shedding
+process. The other two types of locomotion, sidewinding and concertina,
+have not, to my knowledge, been observed in the cottonmouth.
+
+Both the cottonmouth and the cantil have definite affinities for water
+and are as likely to be found in water as out of it. Copperheads and
+rattlesnakes, although not aquatic, are good swimmers. When swimming, a
+motion resembling horizontal undulatory progression is used.
+
+
+Disposition
+
+The number of different opinions expressed in the literature concerning
+the cottonmouth's disposition is not at all surprising. As with any
+species there is a wide range of individual temperament, which is
+affected by many factors. The cottonmouth is considered by some writers
+to be docile while others consider it to be highly dangerous. Allen and
+Swindell (1948:7) described the variability in temperament, even among
+individuals. They wrote: "On rare occasions, moccasins are found which
+will attack. A perfectly docile snake will turn and bite viciously
+without any apparent reason." They also recounted a case in which a
+cottonmouth was kept as a pet for six years, being allowed the freedom
+of the house. Smith and List (1955:123) found them "... surprisingly
+docile in the gulf region [Mississippi], displaying none of the
+pugnacity of more northern cottonmouths." Smith (1956:310) stated:
+"Unlike the copperhead, cottonmouths are pugnacious; their powerful
+jaws, long fangs, vicious disposition and potent venom make them a very
+dangerous animal."
+
+My own observations are in general agreement with the statements of
+Allen and Swindell (_loc. cit._). In my encounters with cottonmouths, I
+have never found any aggressive individuals except for three juveniles
+that were born in captivity. In their first three days in the laboratory
+these juveniles were observed to strike repeatedly whenever anyone
+entered the room. After this short period of aggressiveness, however,
+they slowly became more docile. The disposition shown by the newborn
+young is clearly an innate behavioral pattern that undoubtedly has a
+direct relationship to survival. The majority of cottonmouths that I
+have approached in the field have moved swiftly to seek refuge in nearby
+water; a few have remained motionless as I approached, and one showed
+the typical threat display. Upon capture and handling, they react
+similarly to other pit-vipers by opening and closing the mouth and
+erecting the fangs in an attempt to bite. They often bite through the
+lower jaw and eject venom at this time as well as when the mouth is
+open. Of more than a dozen individuals kept in captivity, four were
+particularly difficult to handle whereas another was extremely docile.
+It was almost never found in aggregations with the other snakes and did
+not struggle or attempt to bite when handled. The majority remained
+unpredictable in disposition, usually appearing docile and lazy but
+capable of extremely rapid movements when disturbed.
+
+
+Defense and Escape
+
+The typical threatening posture of rattlesnakes is all but lacking in
+the cottonmouth, which relies primarily on concealing coloration or
+nearness to water for escape. When approached, it usually plunges into
+nearby water or remains motionless with the head held up at a 45° angle
+and the mouth opened widely exposing the white interior. The tail is
+sometimes vibrated rapidly and musk is expelled. This threat display is
+unique to cottonmouths; although it does not attract as much attention
+as the display of rattlesnakes, it is probably an effective warning to
+most intruders at close range.
+
+Neill (1947:205) reported one case in which a cottonmouth used the "body
+blow" defense, described for _Crotalus_ by Cowles (1938:13), when
+approached by a king-snake, _Lampropeltis getulus_. In this unusual
+posture the anterior and posterior portions of the body are held against
+the ground and the middle one-fourth to one-third of the body is lifted
+up and used in striking the intruder. This same defense posture also was
+observed in rattlesnakes when presented with the odor of the spotted
+skunk, _Spilogale phenax_. However, the "king-snake defense posture" is
+probably not a well-established behavioral pattern in the cottonmouth,
+for it sometimes feeds upon king-snakes. I observed the killing and
+devouring of a cottonmouth by a speckled king-snake, _L. g. holbrooki_;
+the only attempts to escape were by rapid crawling and biting.
+
+Cottonmouths often squirt musk as a defensive action. The tail is
+switched back and forth, and musk is emitted from glands on each side of
+the base of the tail. The fine jets of musk are sprayed upward at about
+45° angles for a distance of nearly five feet. How often this defense
+mechanism is used against other animals is not known, but the musky odor
+can frequently be detected in areas where cottonmouths are common. The
+odor is repulsive and, if concentrated, can cause nausea in some
+individuals. To me, the scent is indistinguishable from that of the
+copperhead.
+
+
+"Head Bobbing"
+
+"Head bobbing" in snakes has been described frequently in the
+literature, and many interpretations have been advanced to explain its
+occurrence. One of the earlier accounts was that of Corrington (1929:72)
+describing behavior of the corn snake, _Elaphe guttata_. Characteristic
+bobbing occurred when the snake was cornered, and seemingly the purpose
+was to warn or frighten foes. Neill (1949:114-115) mentioned the jerking
+or bobbing of the head in several species of snakes including the
+cottonmouth, and remarked that "it is apparently connected with
+courtship and with the recognition of individuals." According to Munro
+(1950:88), "head bobbing" appears to be a sign of annoyance in some
+instances but is usually concerned with reproduction and individual
+recognition. Richmond (1952:38) thought that many types of head
+movements among not only reptiles but also birds and some mammals are a
+result of poor vision and serve "to delimit and orient an object that
+for lack of motion is otherwise invisible." Head movements undoubtedly
+occur in animals to facilitate accommodation, but it is obvious from
+Richmond's conclusions that he has never observed "head bobbing" in
+snakes. The term itself is grossly misleading and should be discarded.
+Mansueti (1946:98) correctly described the movements as spastic
+contractions of the body. I have observed numerous instances of these
+movements in cottonmouths, copperheads, and rat snakes (_Elaphe
+obsoleta_); and in no case has the movement resembled a head bob as is
+described in lizards and other animals. The movement appears to be a
+result of a nervous or sexually excited state and consists of highly
+spastic contractions confined to the anterior part of the snake most of
+the time but affecting the entire body on some occasions.
+
+I found the response to be most common among cottonmouths in confinement
+when food was introduced to a cage containing several individuals
+(increasing the tendency to strike at a moving object) and when an
+individual was placed back in the cage after being handled. At these
+times the snakes that were inactive began to jerk for a few seconds.
+When the snake is in this seemingly nervous state, the same response is
+elicited by another snake crawling over it. At other times the movement
+of one individual causes no such response. The jerking movements appear
+to be released by the recognition of a nervous state in another
+individual and may serve to protect the jerking individual from
+aggressive advances of the former.
+
+Where courtship is involved, the jerking motions are made in conjunction
+with writhing of the male and do not result from the same type of
+releaser described above.
+
+
+Combat Dance
+
+The so-called combat dance between male snakes has long been known, but
+its significance is still poorly understood. It was for many years
+believed to be courtship behavior until the participants were examined
+and found to be males. Carr and Carr (1942:1-6) described one such
+instance in two cottonmouths as courtship. In their observations, as
+well as those of others, copulation was never observed following the
+"dance" but was assumed to be the ultimate goal. After the discovery
+that only males participated, it was suggested that combat involved
+competition for mates, but the "dance" has been observed at times other
+than the breeding season (Ramsey, 1948:228).
+
+Shaw (1948:137-145) discussed the combat of crotalids in some detail but
+drew no conclusions as to the cause of the behavior. Lowe (1948:134)
+concluded with little actual evidence that combat among male snakes is
+solely for territorial purposes. Shaw (1951:167) stated that combat may
+occur as a possible defense against homosexuality. One case of
+homosexual mating among cottonmouths was reported (Lederer,
+1931:651-653), but the incomplete description seems to be of normal
+courtship procedure except that the "female" tried to avoid the male.
+Two instances of combat observed between timber rattlesnakes (_C. h.
+horridus_) by Sutherland (1958:23-24) were definitely initiated because
+of competition for food. More observations are needed before the
+significance of the combat can be fully understood.
+
+
+
+
+THE VENOM
+
+Properties of the Venom
+
+
+The venom and poison apparatus have developed primarily as a means of
+causing rapid death in small animals that are the usual prey. As a
+protective device against larger enemies, including man, the venom may
+have some value; but this was probably unimportant in the evolution of
+the poison mechanism. A secondary function of the venom is to begin
+digestion of tissues of the prey. Since food is swallowed whole,
+injection of digestive enzymes into the body cavity enhances digestion
+of the prey.
+
+Kellogg (1925:5) described venom as a somewhat viscid fluid of a
+yellowish color and composed of 50 to 70 per cent proteins, the chief
+remaining components being water and carbohydrates, with occasional
+admixtures of abraded epithelial cells or saprophytic microorganisms.
+Salts, such as chlorides, phosphates of calcium, magnesium, and
+ammonium, occur in small quantities. Each of the components of snake
+venom has a different effect on the body of the victim. It was at first
+believed that there were two types of venoms: neurotoxic, which acts
+upon nervous tissue; and haemotoxic, which acts on blood and other
+tissues. It has since been found that venoms are composed of varying
+mixtures of both types. Fairley (1929:301) described the constituents of
+venom as: (1) neurotoxic elements that act on the bulbar and spinal
+ganglion cells of the central nervous system; (2) hemorrhagins that
+destroy the lining of the walls of blood vessels; (3) thrombose,
+producing clots within blood vessels; (4) hemolysins, destroying red
+blood corpuscles; (5) cytolysins that act on leucocytes and on cells of
+other tissues; (6) elements that retard coagulation of the blood; (7)
+antibactericidal substances; and (8) ferments that prepare food for
+pancreatic digestion. Elapid snakes tend to have more of elements 1, 4,
+and 6 in their venoms, while viperids and crotalids, of which the
+cottonmouth is one, have higher quantities of elements 2, 3, and 5.
+Kellogg (_loc. cit._) stated that venom of cottonmouths contains more
+neurotoxin than that of rattlesnakes and not only breaks down the nuclei
+of ganglion cells but also produces granular disintegration of the
+myelin sheath and fragmentation of the conducting portions of nerve
+fibers.
+
+Thus, venoms contain both toxic elements and non-toxic substances that
+promote rapid spreading of the venom through the body of the victim.
+Jacques (1956:291) attributed this rapid spreading to the hyaluronidase
+content of venoms.
+
+
+Venom Yield and Toxicity
+
+One of the most important yet undeterminable factors of the gravity of
+snakebite is the amount of venom injected into the victim. Since this
+volume varies considerably in every bite, attempts have been made to
+determine the amount and toxicity of venom produced by each species of
+poisonous snake. Individual yield is so variable that a large number of
+snakes must be milked in order to determine the average yield. Even then
+there remains an uncertainty as to how this amount may compare with that
+injected by a biting snake.
+
+Wolff and Githens (1939b:234) made 16 venom extractions from a group of
+cottonmouths in a two-year period. The average yield per snake
+fluctuated between 80 and 237 milligrams (actual weight), and toxicity
+measured as the minimum lethal dose for pigeons varied from 0.05 to 0.16
+milligrams (dry weight). No decrease in yield or toxicity was evident
+during this period. Another group of cottonmouths from which venom was
+extracted over a period of five years also showed no decrease in yield
+or toxicity. Of 315 individual extractions the average amount obtained
+from each individual was 0.55 cubic centimeters of liquid or 0.158 grams
+of dried venom (28.0 per cent solids). The minimum lethal dosage (M. L.
+D.) which was determined by injecting intravenously into 350-gram
+pigeons was found to be 0.09 milligrams (dry weight). Each snake carried
+approximately 1755 M. L. D.'s of venom.
+
+The record venom extraction for the cottonmouth was 4.0 cubic
+centimeters (1.094 grams dried venom) taken from a five-foot snake which
+had been in captivity for 11 weeks and milked five weeks earlier (Wolff
+and Githens, 1939a:52). The average yield of venom of cottonmouths is
+about three times the average yield reported for copperheads by Fitch
+(1960:256), a difference correlated with the greater bulk and relatively
+large head of the cottonmouth.
+
+Allen and Swindell (1948:13) stated that cottonmouth venom rates third
+in potency, compared drop for drop to that of _Micrurus fulvius_ and
+_Crotalus adamanteus_. Freshly dried cottonmouth venom tested on young
+white rats showed the lethal dose to be from 23 to 29 milligrams per
+kilogram of body weight. The venom of 11 one-week-old cottonmouths was
+found to be more potent than that of adult males. Githens (1935:171)
+rated _C. adamanteus_ venom as being weaker than that of the copperhead
+(_A. contortrix_), which he rated only slightly lower than cottonmouth
+venom. The crotalids which he ranked more toxic than cottonmouths are:
+the Pacific rattlesnake (_C. viridis oreganus_) and the massasauga (_S.
+catenatus_). He found _A. bilineatus_, _C. durissus_, and _C. v.
+lutosus_ to have the same toxicity as cottonmouths. Minton (1953:214)
+found that the intraperitoneal "lethal dose 50" (the dose capable of
+killing half the experimental mice receiving injections of it) was 6.36
+milligrams per kilogram for copperheads. However, in later publications
+Minton (1954:1079; 1956:146) reported that the "lethal dose 50" for
+copperheads was 25.65 milligrams. Approximately the same potency was
+determined for cottonmouths. Several rattlesnakes that he tested showed
+a higher toxicity than copperheads or cottonmouths.
+
+Criley (1956:378) found the venom of copperheads to be 6.95, nearer
+Minton's earlier estimate, and rated cottonmouth venom as being twice as
+toxic as that of copperheads. The relative toxicities of other crotalids
+tested, considering the cottonmouth to be one unit, were: _C.
+basiliscus_, 0.3; _A. contortrix_, 0.5; _C. viridis oreganus_, 1.4; _A.
+bilineatus_, 2.2; _C. adamanteus_, 2.3; _C. v. viridis_, 3.2; _C.
+durissus terrificus_, 27.5.
+
+It can be seen from the above examples that toxicity of venoms and the
+resistance of the animal receiving an injection of venom is highly
+variable. Possibly the venom of each species of snake has greatest
+effect on animals of the particular group relied on for food by the
+snake. If that is so, the venom of cottonmouths would be expected to be
+more toxic when tested on fish, reptiles, and amphibians than on birds
+and mammals. Likewise, the venom of most species of rattlesnakes would
+be expected to be more virulent when injected into mammals than when
+injected into lower vertebrates. But, according to Netting (1929:108),
+species of rattlesnakes that prey on cold-blooded animals, which are
+less susceptible to venoms than warm-blooded animals, are thought to
+have highly toxic venoms. This explanation accounts for the powerful
+venom of _Sistrurus catenatus_; and, in this respect, venom of
+cottonmouths should be highly toxic also. However, no clear-cut trends
+have been shown in most cases. Allen (1937) injected 250-gram guinea
+pigs with 4 milligrams of venom of various poisonous snakes. Survival
+time was recorded in order to indicate the relative potency of the
+venoms. Of 16 such tests _C. adamanteus_ held places 1, 2, 3, 12, and
+16; _Bothrops atrox_ held places 4, 9, 10, and 13; and _A. piscivorus_
+held places 5, 7, 8, and 15. Places 6, 11, and 14 were held by three
+individuals of different species. No relationship to size or sex was
+indicated by the results of this experiment.
+
+
+Susceptibility of Snakes
+
+Numerous experiments have been conducted to determine the susceptibility
+of various snakes to venom. The majority of these experiments were
+performed to learn whether or not venomous snakes were immune to their
+own poison. Conant (1934:382) reported on a 30-inch cottonmouth that
+killed two Pacific rattlesnakes and another cottonmouth. One rattlesnake
+was bitten on the tail and the other on or near the head and partially
+swallowed. Gloyd (1933:13-14) recorded fatal effects to a rattlesnake
+from the bite of a cottonmouth. He also reported on the observations of
+three other crotalids bitten by themselves or other snakes, from which
+no harmful effects were observed. Allen (1937) injected several snakes
+with dried cottonmouth venom which was diluted with distilled water just
+before each injection. Four cottonmouths receiving 9, 18, 19, and 20
+milligrams of venom per ounce of body weight survived, while another
+receiving 18.7 milligrams per ounce died after three hours. A specimen
+of _S. miliarius_ receiving 8.3 milligrams per ounce died in about ten
+hours, while a _C. durissus_ receiving 12.5 milligrams per ounce
+succumbed in 45 minutes. An alligator receiving 6 milligrams per ounce
+died in 14 hours. Even the snakes that survived showed some degree of
+swelling.
+
+The studies of Keegan and Andrews (1942:252) show that king-snakes are
+sometimes killed by poisonous snakes. A _Lampropeltis calligaster_
+injected with _A. contortrix_ venom (0.767 milligrams per gram) died
+five days following the injection. This amount was more than twice the
+amount of _A. piscivorus_ venom injected into a _L. getulus_ by Allen
+(1937) in which the snake showed no ill effects. Keegan and Andrews
+(_loc. cit._) stated that success in overpowering and eating poisonous
+snakes by _Lampropeltis_ and _Drymarchon_ may be due to the ability to
+avoid bites rather than to immunity to the venom. However, Rosenfeld and
+Glass (1940) demonstrated that the plasma of _L. g. getulus_ had an
+inhibiting effect on the hemorrhagic action on mice of the venoms of
+several vipers.
+
+One of the more extensive studies on effects of venoms on snakes is that
+by Swanson (1946:242-249). In his studies freshly extracted liquid venom
+was used. His studies indicated that snakes are not immune to venom of
+their own kind or to closely related species. Copperhead venom killed
+copperheads faster than did other venoms but took more time to kill
+massasaugas, cottonmouths, and timber rattlers. However, most of the
+snakes were able to survive normal or average doses of venom although
+they are not necessarily immune to it.
+
+One of the major problems in comparing the data on toxicity of venom in
+studies of this type is that no standard method of estimating toxicity
+has been used. Swanson's (_loc. cit._) amount of venom equalling one
+minim (M.L.D.?) ranged from 0.058 to 0.065 cubic centimeters. There were
+no different values given for each species, but the time that elapsed
+from injection of the venom to death represented the toxicity. There
+also was no attempt in his study to convert the amount of venom used
+into a ratio of the volume of venom per weight of snake, making the
+results somewhat difficult to interpret. Additional work in this field
+should provide for many injections into many individuals of several size
+classes. The studies to date have been on far too few individuals to
+allow statistical analyses to be accurate.
+
+
+
+
+THE BITE
+
+Effects of the Bite
+
+
+Factors determining the outcome of snakebite are: size, health, and
+species of snake; individual variation of venom toxicity of the species;
+age and size of the victim; allergic or immune responses; location of
+the bite; and the amount of venom injected and the depth to which it is
+injected. The last factor is one of the most variable, owing to (1)
+character and thickness of clothing between the snake and the victim's
+skin, (2) accuracy of the snake's strike, and (3) size of the snake,
+since a large snake can deliver more venom and at a greater depth than
+can a small snake.
+
+Pope and Perkins (1944) demonstrated that pit-vipers of the United
+States bite as effectively as most innocuous snakes and that a careful
+study of the bite may reveal the location of the pocket of venom, size
+of the snake, and possibly its generic identity (see Dentition). The
+bite pattern of the cottonmouth as well as the other crotalids showed
+the typical fang punctures plus punctures of teeth on both the pterygoid
+and mandible. Even so, a varying picture may be presented because from
+one to four fang marks may be present. At times in the fang-shedding
+cycle three and even four fangs can be in operation simultaneously.
+
+Various authors have attributed death of the prey to the following
+causes: paralysis of the central nervous system, paralysis of the
+respiratory center, asphyxiation from clotting of the blood, stoppage of
+the heart, urine suppression due to crystallized hemoglobin in the
+kidney tubules, dehydration of the body following edema in the area of
+the bite, or tissue damage. Mouths of snakes are reservoirs for
+infectious bacteria, which are especially prolific in damaged tissue.
+Bacterial growth is aided by the venom which blocks the bactericidal
+power of the blood.
+
+Three grades in the severity of snakebite (I, minimal; II, moderate; and
+III, severe) were described by Wood, Hoback, and Green (1955). Parrish
+(1959:396) added a zero classification to describe the bite of a
+poisonous snake in which no envenomation occurred. Grade IV (very
+severe) was added by McCollough and Gennaro (1963:961) to account for
+many bites of the eastern and western diamondback rattlesnakes.
+
+The first symptom of poisonous snakebite is an immediate burning
+sensation at the site of the bite. Within a few minutes the loss of
+blood into the tissues causes discoloration. Swelling proceeds rapidly
+and can become so great as to rupture the skin. Pain is soon felt in the
+lymph ducts and glands. Weakness, nausea, and vomiting may ensue at a
+relatively early stage. Loss of blood into tissues may spread to the
+internal organs. In conjunction with a rapid pulse, the blood pressure
+and body temperature can drop. Some difficulty in breathing can occur,
+especially if large amounts of neurotoxin are present in the venom. In
+severe cases the tension due to edema obstructs venous and even arterial
+flow, in which case bacteria may multiply rapidly in the necrotic tissue
+and gangrene can occur. Blindness due to retinal hemorrhages may occur.
+Symptoms of shock may be present after any bite.
+
+
+Treatment
+
+Perhaps one of the most important factors in the outcome of snakebite is
+the treatment. Because of the variable reactions to snakebite, treatment
+should vary accordingly. Many methods have been proposed for treating
+snakebite, and there is disagreement as to which is the best. The list
+of remedies that have been used in cases of snakebite includes many that
+add additional injury or that possibly increase the action of the venom.
+The use of poultices made by splitting open living chickens and the use
+of alcohol, potassium permanganate, strychnine, caffeine, or injection
+of ammonia have no known therapeutic value, and may cause serious
+complications. The most important steps in the treatment of snakebite
+are to prevent the spread of lethal doses of venom, to remove as much
+venom as possible, and to neutralize the venom as quickly as possible.
+
+It is generally agreed that the first step in snakebite treatment should
+be to place a ligature above the bite to restrict the flow of venom, and
+also to immobilize the patient as much as possible. The ligature should
+be loosened at least every fifteen minutes. The next steps are
+sterilization of the skin and the making of an incision through the fang
+punctures. As pointed out by Stahnke (1954:8), the incision should be
+made in line with the snake's body at the time of the bite, so as to
+account for the rearward curvature of the fangs and possibly to reach
+the deposition of venom. Many instruction booklets and first-aid guides
+have specified the length and depth of incision to be made, but the
+actual size and depth of the cut should depend upon the location of the
+bite. An "X" cut or connection of the fang punctures is likely to
+facilitate the spread of the venom. No cut should be made that would
+sever a large blood vessel or ligament.
+
+Extensive damage is often caused by well-meaning individuals whose
+attempts at first aid result in brutally deep incisions and tourniquets
+applied too tightly and for too long a period of time; the resultant
+damage in many instances exceeds that of the bite itself (Stimson and
+Engelhardt, 1960:165). Stimson and Engelhardt also think that time
+should be sacrificed to surgical cleanliness, and incisions should not
+be made if a hospital can be reached within an hour.
+
+The ligature-cryotherapy (L-C) method proposed by Stahnke (1953) has
+been severely criticized by other workers. He stated that the ligature
+should be tight enough to restrict completely the flow of venom until
+the temperature of the area can be lowered sufficiently to prevent any
+action of the venom. After 10 minutes the ligature may be removed and
+the bitten area kept immersed in a vessel of crushed ice and water. If
+the envenomized member is to be treated for more than four hours (which
+is the case with almost all pit-viper bites), it should be protected by
+placing it in a plastic bag. The venom action should be tested after 12
+or more hours. This consists of a brief warming period to determine
+whether or not the action of the venom can be felt. The patient should
+be kept warm at all times; and the warming at the termination of
+treatment should be done gradually, preferably by allowing the water to
+warm slowly to room temperature.
+
+Advocates of the L-C method warn against making incisions unless they
+are absolutely necessary, the theory being that each cut permits
+additional bacterial infection and does little good in removing venom.
+However, McCollough and Gennaro (1963:963) demonstrated that, in bites
+where the fangs had only slightly penetrated the skin, more than 50 per
+cent of the venom was removed in some instances if suction was started
+within three minutes after the injection. With deeper injection the
+amount of venom recovered sometimes reached 20 per cent of the dose.
+Stahnke suggested that an incision be made at the site of the bite only
+after the site has been refrigerated for at least 30 minutes.
+
+Stimson and Engelhardt (_loc. cit._) stated that two constricting bands
+should be used between the bite and the body and that cracked ice in a
+cloth should be applied to the bite before reaching a hospital. In
+addition, they suggested the following procedure. Rings of incisions
+should follow the swelling, and suction should continue for several
+hours. After the edema has receded, the limb should be wrapped in a
+towel containing crushed ice. Antivenin should be given only in severe
+cases. Calcium gluconate and gas gangrene antitoxin as well as
+antibiotics are helpful.
+
+The most recent and up-to-date summary of snakebite treatment is that by
+McCollough and Gennaro (1963). Following is a brief summary of their
+suggestions:
+
+     1. Immobilization--Systemic immobilization is effected by body
+     rest and locally by splinting the bitten area.
+
+     2. Tourniquet--A lightly occlusive tourniquet during a 30- to
+     60-minute period of incision and suction would seem to possess
+     some advantages. In severe cases where medical attention is
+     hours away, a completely occlusive tourniquet may be necessary
+     to prevent death. Sacrifice of the extremity may be necessary
+     for the preservation of life.
+
+     3. Incision and suction--Suction should begin three to five
+     minutes after injection of venom if symptoms of poisoning are
+     present. Incisions one-fourth inch to an inch long across each
+     fang mark should be made in order to open the wound for more
+     efficient suction. Multiple incisions are not useful for the
+     removal of venom but may be employed under hospital conditions
+     to reduce subcutaneous tensions and ischemia.
+
+     4. Cryotherapy--An ice cap over the site of the bite for relief
+     of pain would seem to be permissible, especially prior to the
+     administration of antivenin. It must be remembered that cooling
+     during the administration of the antivenin radically reduces
+     the access of the antiserum to the bite area.
+
+     5. Antivenin--Antiserum is the keystone to the therapy of
+     snakebite. Careful evaluation of the severity of the bite and
+     the patient's sensitivity should be made before the use of
+     antivenin. In Grade II (moderate) bites, the intramuscular
+     injection on the side of the bite may suffice. In Grades III
+     (severe) and IV (very severe), shock and systemic effects
+     require intravenous injection. In bites producing symptoms of
+     this severity, antivenin must be given in amounts large enough
+     to produce clinical improvement. Ten to 20 units may be
+     necessary to prevent the relapse that sometimes occurs after
+     small doses of antivenin. Permanent remission of swelling and
+     interruption of necrosis are the therapeutic end point in the
+     clinical use of the antiserum.
+
+In all cases of snakebite where there is any doubt as to the snake's
+identity, it should be killed if possible and taken to the hospital for
+positive identification. In many instances of actual bites by poisonous
+snakes the only treatment needed was an injection of tetanus antitoxin
+or toxoid and sedation, because physical examination revealed no
+indication of poisoning (Stimson and Engelhardt, _loc. cit._).
+
+
+Case History of a Bite
+
+On July 29, 1963, at 8:20 a.m., I was treating a nine-month-old
+cottonmouth for mites. As I dropped the snake into a sink, it twisted
+its head and bit the tip of my right middle finger with one fang. The
+fang entered just under the fingernail and was directed downward, the
+venom being injected about five millimeters below the site of fang
+penetration. After placing the snake back in its cage, I squeezed the
+finger once to promote bleeding, wrapped a string around the base of the
+finger, and drove to Watkins Memorial Hospital on the University of
+Kansas campus. I began to feel a burning sensation in the tip of the
+finger almost immediately. Upon my arrival at the hospital, an
+additional ligature was placed around my wrist. At 8:30 a.m. a small
+incision was made in the end of the finger, which by this time was
+beginning to darken at the point of venom deposition. I sucked on the
+finger until 8:35 a.m., when a pan of ice water that I had requested was
+brought to me. No pain was felt except that caused by the ice. Fresh ice
+was added as needed to keep the temperature low. By 9:30 a.m. the
+finger had swollen and stiffened. At 10:00 a.m. the swelling had
+progressed to the index finger and back of the hand. I experienced
+difficulty in opening and closing the hand. Blood oozed slowly from the
+incision. A dull ache persisted and about every two to four minutes a
+sharp throb could be felt until nearly 11:00 a.m., when the pain
+diminished. The rate and intensity of throbbing increased whenever the
+hand was removed from the ice bath for more than a few seconds. Although
+only the hand was immersed, the entire forearm was cold. Pain was felt
+along the lymphatics on top of the arm when it was touched, and by 1:00
+p.m. a slight pain could be felt in the armpit. Since swelling and pain
+were almost nonexistent by 2:00 p.m., I was permitted to leave. After
+walking to a nearby building, I again felt a burning sensation as the
+hand warmed. I made another ice bath and again immersed the hand in it
+until 4:10 p.m., at which time it was removed from the water. The pain
+and swelling began anew, and the hand was placed back in an ice bath
+from 5:30 p.m. until about 7:30 p.m. At this time cryotherapy was
+discontinued. From 10:00 p.m. to 12:00 midnight my legs twitched
+periodically, and pain could be felt in both armpits. A slight
+difficulty in breathing also was experienced for a short time. The acute
+pain and burning sensation remained in the finger until the following
+morning, but swelling progressed only as far as the wrist. The only
+discomfort that day was in the finger. The tip was darkened, the entire
+first digit red and feverish, and the lymphatics still painful when
+touched. By the third day the swelling had regressed. The incision
+itself was the main cause of discomfort, and the soreness at the site of
+the bite persisted for at least four days.
+
+Although the L-C method of snakebite treatment has been vigorously
+attacked by many, there is still need of much more data before it
+can be unequivocally condemned or praised. It was preferred in the
+treatment of this bite because: I knew that envenomation was minimal
+and that there would be no need for antivenin; only one fang of a
+snake less than one foot long had entered the tip of the finger; the
+snake had bitten three frogs in the previous two days and had
+possibly used up a considerable amount of its venom; the venom was
+deposited at such a shallow depth that at least a portion of it
+could be removed by suction; and the wound bled freely even before
+suction was applied. The ice water was uncomfortably cold but was
+not cold enough to cause frostbite, a major objection to the L-C
+method. Ideally, fresh ice should be added little by little to
+replace that which is melting, and the immersed area should be
+protected from the water by a plastic bag. Pain and swelling can be
+minimized by cryotherapy, but I would recommend its use only in
+cases of mild poisoning such as the one described herein.
+
+
+Snakebite in the United States
+
+Many estimates have been made of the number of bites of poisonous snakes
+that occur annually in the United States. The occurrence of poisonous
+snakebite has been nearly as badly underestimated as fatal results of
+their envenomations have been overrated. For important data on number of
+persons bitten by poisonous snakes in the United States, see the
+following: Allen and Swindell (1948:15); Githens (1935:172); Klauber
+(1956:811); Parrish (1963); Sowder and Gehres (1963:973); Stimson and
+Engelhardt (1960:153); Swaroop and Grab (1956:441); Swartzwelder
+(1950:579); Willson (1908:530); and Wood (1954b:937).
+
+Judging from estimates made in several states, the number of poisonous
+snakebites in the United States would be about 5000 per year. In the
+region where the cottonmouth occurs there are approximately 2000 persons
+bitten annually by poisonous snakes. Of these approximately 39 per cent
+are copperhead bites, 30 per cent each are cottonmouth and rattlesnake
+bites, and I per cent are coral snake bites. These percentages vary
+considerably from place to place, because of the distribution and
+abundance of the eight species of poisonous snakes whose ranges overlap
+that of the cottonmouth.
+
+According to Parrish (1963), about 14 people die of snakebite each year
+in the United States. Of these deaths, about 6.6 per cent are
+attributable to cottonmouths, 77.0 per cent to rattlesnakes, and 1.6 per
+cent to coral snakes; 14.8 per cent are unidentified. Almost half of the
+fatalities are in persons less than 20 years of age, the high mortality
+rate being partially due to the greater ratio of venom to body weight.
+
+
+
+
+SUMMARY
+
+
+In my study, 306 living and preserved cottonmouths were examined. This
+species occurs throughout the coastal plains of the southeastern United
+States, usually at altitudes of less than 500 feet but occasionally up
+to altitudes of more than 2000 feet.
+
+Two subspecies are recognized: the eastern cottonmouth, _A. p.
+piscivorus_, occurring from extreme eastern Mississippi to southeastern
+Virginia and Florida; and the western cottonmouth, _A. p. leucostoma_,
+occurring from eastern Mississippi northward to southern Illinois and
+Missouri and westward to central Texas. Intergradation occurs in eastern
+Mississippi.
+
+The northern edge of the range is probably limited by low temperatures
+in winter, and the western edge by lack of available habitat resulting
+from insufficient precipitation. Old records of occurrence indicate that
+the range has decreased in the last 100 years. The species inhabits
+mostly areas where water is found, but at times wanders a mile or more
+from the nearest water.
+
+The ground color is predominantly a brown, but varies from a
+brownish-green to almost black with a pattern of 10 to 17 irregular
+bands of a darker shade of brown. The pattern is better defined in the
+eastern subspecies than in the western.
+
+The scutellation resembles that of other species of _Agkistrodon_. In
+the specimens examined supralabials ranged from 7 to 9, and infralabials
+from 8 to 12. The number of dorsal scale rows on the neck, at mid-body,
+and immediately anterior to the anus is relatively constant at 27-25-21,
+respectively. Ventral scales of 34 males averaged 134.4 (128 to 139),
+and those of 48 females 133.5 (128 to 137). The number of caudal scales
+showed some degree of sexual dimorphism; the average was 45.4 (41 to 50)
+in 34 males and 42.6 (39 to 49) in 44 females. In general, caudal scales
+on the basal half of the tail are undivided, whereas those on the distal
+half are divided. No marked geographical variation was found in any
+scale character.
+
+The poison fangs vary in length from 1.3 per cent of snout-vent length
+in juveniles to 1.0 per cent in large adults. Fangs of captive
+cottonmouths were shed and replaced at intervals of about 21 days, but
+the interval was variable. Relationships in distance between the base of
+fangs and between fang punctures in an actual bite indicate that
+examination of the wound does not provide a good basis for judging
+accurately the size of the snake that inflicted the bite.
+
+In general, females less than 450 millimeters in snout-vent length were
+juveniles; those more than 450 millimeters were classified as post
+partum or reproductive on the basis of sizes of ovarian follicles. Since
+about half the adult females were fecund, it was concluded that a
+biennial reproductive cycle occurs in this species. An annual cycle may
+occur in areas where temperature permits year-round activity. It was
+estimated that females become sexually mature at an age of approximately
+two and one-half years. Mating is probably most concentrated in early
+spring at about the time when females ovulate, but copulation is not a
+stimulus for ovulation. Sperm retention and delayed fertilization allow
+young to be produced without copulation occurring in each breeding
+season. The testes increase in size gradually rather than rapidly at
+maturity or in each breeding season, but seasonal cycles in sperm
+production occur.
+
+The gestation period is three and one-half to four months. Determination
+of sex in the embryos is possible by late June, because the hemipenes of
+males are evaginated until the time of birth. Parturition generally
+occurs in August or September, but captivity may delay birth for a month
+or more. From one to 16 young per litter are born, depending on size of
+the mother and other factors; but the average is between six and seven.
+Mortality rate at birth is high in captive individuals but has not been
+determined in natural populations. The sex ratio in embryos and adults
+examined revealed about 53 per cent females. Because sufficient
+information on population composition is not available, an estimate of
+the percentage of adults in a natural population was based upon the
+number found in my study. The reproductive potential was estimated from
+these figures.
+
+Normal young at birth are 230 to 240 millimeters in snout-vent length,
+but their size is influenced by the condition of the mother. Comparison
+of newborn young with those captured in spring indicates that little
+growth occurs during winter. Early growth is largely dependent upon
+feeding before winter quiescence.
+
+The umbilical cord is broken at birth and the navel closes within a few
+days, but the scar remains throughout life. Sexual dimorphism in the
+position of the scar is characteristic of some snakes but is minimal in
+cottonmouths.
+
+In those snakes more than 700 millimeters in length, males outnumber
+females three to one. The maximum age of cottonmouths in nature is
+unknown, but one has been kept in captivity for more than 18 years.
+
+Allometric growth is striking in cottonmouths. The head and tail are
+proportionately longer in young individuals than in adults; and in males
+the tail is, on the average, slightly longer than in females of the same
+size.
+
+Shedding of the skin provides for growth and wear in snakes. The young
+shed within a few days after birth and generally shed more frequently
+than adults. Frequency of shedding depends mostly on amount of food
+consumed, and there is some evidence that injuries on the head and neck
+increase the frequency of shedding. Before shedding, the eyes become
+cloudy for about five and one-half days, then clear up again for about
+four days before the skin is shed.
+
+The food of cottonmouths consists mainly of small vertebrates and
+occasionally invertebrates that are found near water. Fish, amphibians,
+and reptiles make up nearly 70 per cent of the diet. Carrion is also
+eaten and cannibalism occurs occasionally. Food is obtained by lying in
+ambush or by active searching. The young are known to lure their prey
+within striking range by waving their yellow tails in a manner
+suggestive of writhing grubs. The method of obtaining prey differs
+according to the kind of prey. Generally, cottonmouths retain their hold
+on fish or frogs but release mice and larger prey after delivering a
+bite.
+
+The major causes of mortality of cottonmouths are obscure. Predators are
+known to include alligators, indigo snakes, king-snakes, largemouth
+bass, and blue herons; there are probably numerous others. Heavy
+parasitic infestations were found among the snakes examined. Snake
+mites, _Ophionyssus natricus_, became increasingly abundant on almost
+all captive snakes in April and May of 1963. Lung flukes (_Ochetosoma_
+sp.) were in 16 of 20 captive snakes, and many preserved specimens
+contained nematodes (_Kalicephalus_ sp.) in the stomach and/or tapeworms
+(_Ophiotaenia_ sp.) in the intestine. Although parasitic infestation
+causes discomfort and may lower resistance to other detrimental factors,
+it is difficult to attribute death to the effect of any particular kind
+of parasite. Miscellaneous causes of death of some captive snakes also
+were discussed.
+
+The maximal body temperatures tolerated by four cottonmouths were
+between 38° and 40° C., but a temperature of 38° was lethal to a fifth
+individual. Cottonmouths have been found on occasion when other snakes
+were inactive because of low temperatures, but minimal temperatures
+tolerated by this species are not known. The annual cycle of activity is
+dependent upon temperature and thus varies from north to south.
+Cottonmouths generally migrate inland in autumn, usually to dry forested
+hillsides, where they den along with other species of snakes. After a
+few warm days in spring they migrate back to the water's edge. The diel
+activity cycle likewise depends upon temperatures but is influenced by
+other factors as well. In spring and autumn, the snakes are active
+mostly on warm, sunny days, whereas in summer they are active mostly at
+night. In order to maintain adequate internal temperatures, much time is
+spent basking mostly in a characteristic flat, resting coil either
+beside a body of water or above water on limbs of dead trees. In this
+position the snake is ready either for a short strike or a hasty
+getaway.
+
+Juveniles appear particularly aggressive and strike repeatedly when
+approached, a behavioral pattern definitely favoring survival. Adults
+vary in disposition, usually appearing sluggish and lazy, but they are
+capable of striking rapidly when disturbed. The typical threat display
+consists of lying in a coiled position with the mouth opened widely,
+exposing the white interior, and with the tail vibrating rapidly. The
+striking posture resembles the resting coil except that the anterior
+part of the body is raised off the ground and the mouth is sometimes
+opened. Musk is often ejected in a fine spray from glands in the tail as
+a further defensive action.
+
+"Head bobbing," more properly described as spastic contractions of the
+body, was observed in captives when food was introduced into a cage
+containing several individuals or when one of the snakes was returned to
+the cage after being handled. Reports in the literature also have
+connected these jerking movements with courtship. The response appears
+to be elicited whenever a nervous state is recognized in another
+individual and may serve to protect the jerking individual from
+aggressive advances of the former.
+
+The relatively heavy appearance of the body, sluggish habits, and
+cryptic coloration are correlated with the development of venom and
+fangs. The poison apparatus has developed primarily as a means of
+causing rapid death in prey and secondarily, perhaps, to begin the
+digestion of small animals that are the usual prey, but it is also
+important as a defensive device. The venom contains at least eight
+constituents that aid in its action on prey. Toxicity of the venom is
+difficult to determine because of numerous variables, but cottonmouth
+venom is generally believed to be less potent than that of most
+rattlesnakes and more potent than that of the copperhead. Snakes in
+general are more resistant to snake venoms than other vertebrates of
+similar size, but there is no immunity even to their own venom.
+
+About ten per cent of the approximately 5000 bites of poisonous snakes
+per year in the United States are attributable to cottonmouths, and
+about seven per cent of the approximately 14 deaths per year are caused
+by cottonmouths.
+
+
+
+
+LITERATURE CITED
+
+
+ALLEN, E. R.
+
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+
+ALLEN, E. R., and SWINDELL, D.
+
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+     supplement).
+
+ALLEN, M. J.
+
+     1932. A survey of the amphibians and reptiles of Harrison County,
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+
+ANDERSON, P.
+
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+
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+
+ANON.
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+
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+
+BAILEY, R. M.
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+
+BARBOUR, R. W.
+
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+
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+
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+
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+
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+
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+DOWLING, H. G.
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+
+     1951b. A proposed method of expressing scale reductions in snakes.
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+
+DUNDEE, H. A., and BURGER, W. L., JR.
+
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+
+EDGREN, R. A.
+
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+
+FAIRLEY, N. H.
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+
+FITCH, H. S.
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+     1956. Temperature responses in free-living amphibians and reptiles
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+
+FORCE, E. R.
+
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+
+FOX, W.
+
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+
+GITHENS, T. S.
+
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+
+GLISSMEYER, H. R.
+
+     1951. Symposium. A snake den in Tooele County, Utah. Egg production
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+
+GLOYD, H. K.
+
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+
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+
+GLOYD, H. K., and CONANT, R.
+
+     1943. A synopsis of the American forms of _Agkistrodon_
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+
+GOODMAN, J. D.
+
+     1958. Material ingested by the cottonmouth, _Agkistrodon
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+
+GUIDRY, E. V.
+
+     1953. Herpetological notes from southeastern Texas. Herpetologica,
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+
+HALL, H. H., and SMITH, H. M.
+
+     1947. Selected records of reptiles and amphibians from southeastern
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+
+HAMILTON, W. J., JR., and POLLACK, J. A.
+
+     1955. The food of some crotalid snakes from Fort Benning, Georgia.
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+
+HERALD, E. S.
+
+     1949. Effects of DDT oil solution upon amphibians and reptiles.
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+
+HICKMAN, C. P.
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+HURTER, J. H.
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+JACQUES, R.
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+     Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv. Sci.,
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+
+KEEGAN, H. L., and ANDREWS, T. F.
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+
+KELLOGG, R.
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+KLAUBER, L. M.
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+KLIMSTRA, W. D.
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+LAUGHLIN, H. E.
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+     1959. Stomach contents of some aquatic snakes from Lake McAlester,
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+LEDERER, G.
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+LOWE, C. H., JR.
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+MANSUETI, R.
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+     1946. Mating of the pilot blacksnake. Herpetologica, 3:98-100, 1
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+
+MARTIN, J. R., and WOOD, J. T.
+
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+     1963. Evaluation of venomous snake bite in the southern United
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+MCILHENNY, E. A.
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+     1935. The alligator's life history. The Christopher Publ. House,
+     Boston, Massachusetts, 117 pp.
+
+MINTON, S. A., JR.
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+
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+
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+
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+
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+
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+
+     1956. The snakebite mortality problem in the world. Pp. 439-466
+     _in_ Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv.
+     Sci., Publ. No. 44).
+
+SWARTZWELDER, J. C.
+
+     1950. Snake-bite accidents in Louisiana with data on 306 cases.
+     Amer. Jour. Trop. Med., 30(4):575-589.
+
+TINKLE, D. W.
+
+     1962. Reproductive potential and cycles in female _Crotalus atrox_
+     from northwestern Texas. Copeia, 1962(2):306-313.
+
+TROWBRIDGE, A. H.
+
+     1937. Ecological observations on amphibians and reptiles collected
+     in southeastern Oklahoma during the summer of 1934. Amer. Midl.
+     Nat., 18(2):285-303.
+
+VOLSØE, H.
+
+     1944. Structure and seasonal variation of the male reproductive
+     organs in _Vipera berus_ (L.). Spolia Zool. Mus. Hauniensis V.
+     Reprint, Copenhagen, pp. 1-172.
+
+WHARTON, C. H.
+
+     1960. Birth and behavior of a brood of cottonmouths, _Agkistrodon
+     piscivorus piscivorus_, with notes on tail-luring. Herpetologica,
+     16:125-129.
+
+WILLSON, P.
+
+     1908. Snake poisoning in the United States: a study based on an
+     analysis of 740 cases. Arch. Int. Med., 1(5):516-570.
+
+WOLFF, N. O., and GITHENS, T. S.
+
+     1939a. Record venom extraction from water moccasin. Copeia,
+     1939(1):52.
+
+     1939b. Yield and toxicity of venom from snakes extracted over a
+     period of two years. Copeia, 1939(4):234.
+
+WOOD, J. T.
+
+     1954a. The distribution of poisonous snakes in Virginia. Virginia
+     Jour. Sci., 5(3):152-167, 4 maps.
+
+     1954b. A survey of 200 cases of snake-bite in Virginia. Amer. Jour.
+     Trop. Med. and Hyg., 3(5):936-943.
+
+WOOD, J. T., HOBACK, W. W., and GREEN, T. W.
+
+     1955. Treatment of snake venom poisoning with ACTH and cortisone.
+     Virginia Med. Month, 82:130-135.
+
+WRIGHT, A. H., and WRIGHT, A. A.
+
+     1957. Handbook of snakes of the United States and Canada. Comstock
+     Publ. Assoc., Cornell Univ. Press, 2:ix + 565-1106 pp.
+
+YAMAGUTI, S.
+
+     1958. Systema helminthum. Interscience Publ., Inc., New York, 3
+     vols., 5 parts, 1:xi + 1575 pp., 2:vii + 860 pp., 3:1261 pp.
+
+YERGER, R. W.
+
+     1953. Yellow bullhead preyed upon by cottonmouth moccasin. Copeia,
+     1953(2):115.
+
+     _Transmitted June 20, 1966._
+
+
+
+
+UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY
+
+
+Institutional libraries interested in publications exchange may obtain
+this series by addressing the Exchange Librarian, University of Kansas
+Library, Lawrence, Kansas. Copies for individuals, persons working in a
+particular field of study, may be obtained by addressing instead the
+Museum of Natural History, University of Kansas, Lawrence, Kansas. When
+copies are requested from the Museum, 25 cents should be included (for
+each 100 pages or part thereof) for the purpose of defraying the costs
+of wrapping and mailing. For certain longer papers an additional amount
+indicated below, toward the cost of production, is to be included.
+Materials published to date in this series are as follows.
+
+* An asterisk designates those numbers of which the Museum's
+supply (not necessarily the Library's supply) is exhausted.
+Materials published to date, in this series, are as follows:
+
+Vol. 1.
+
+     Nos. 1-26 and index. Pp. 1-638, 1946-1950.
+
+*Vol. 2.
+
+     (Complete) Mammals of Washington. By Walter W. Dalquest. Pp.
+     1-444, 140 figures in text. April 9, 1948.
+
+*Vol. 3.
+
+     Nos. 1-4 and index. Pp. 1-681. 1951.
+
+*Vol. 4.
+
+     (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41
+     plates, 31 figures in text. December 27, 1951.
+
+Vol. 5.
+
+     Nos. 1-37 and index. Pp. 1-676, 1951-1953.
+
+*Vol. 6.
+
+     (Complete) Mammals of Utah, _taxonomy and distribution_. By
+     Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables.
+     August 10, 1952.
+
+Vol. 7.
+
+     Nos. 1-15 and index. Pp. 1-651, 1952-1955.
+
+Vol. 8.
+
+     Nos. 1-10 and index. Pp. 1-675, 1954-1956.
+
+Vol. 9.
+
+     Nos. 1-23 and index. Pp. 1-690, 1955-1960.
+
+Vol. 10.
+
+     Nos. 1-10 and index. Pp. 1-626, 1956-1960.
+
+Vol. 11.
+
+     Nos. 1-10 and index. Pp. 1-703, 1958-1960.
+
+Vol. 12.
+
+     *1. Functional morphology of three bats: Eumops, Myotis,
+     Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates, 24 figures
+     in text. July 8, 1959.
+
+     *2. The ancestry of modern Amphibia: a review of the evidence.
+     By Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text. July
+     10, 1959.
+
+     3. The baculum in microtine rodents. By Sydney Anderson. Pp.
+     181-216, 49 figures in text. February 19, 1960.
+
+     *4. A new order of fishlike Amphibia from the Pennsylvanian of
+     Kansas. By Theodore H. Eaton, Jr., and Peggy Lou Stewart. Pp.
+     217-240, 12 figures in text. May 2, 1960.
+
+     5. Natural history of the Bell Vireo. By Jon C. Barlow. Pp.
+     241-296, 6 figures in text. March 7, 1962.
+
+     6. Two new pelycosaurs from the lower Permian of Oklahoma. By
+     Richard C. Fox. Pp. 297-307, 6 figures in text. May 21, 1962.
+
+     7. Vertebrates from the barrier island of Tamaulipas, México.
+     By Robert K. Selander, Richard F. Johnston, B. J. Wilks, and
+     Gerald G. Raun. Pp. 309-345, plates 5-8. June 18, 1962.
+
+     8. Teeth of edestid sharks. By Theodore H. Eaton, Jr. Pp.
+     347-362, 10 figures in text. October 1, 1962.
+
+     9. Variation in the muscles and nerves of the leg in two genera
+     of grouse (Tympanuchus and Pedioecetes). By E. Bruce Holmes.
+     Pp. 363-474, 20 figures. October 25, 1962. $1.00.
+
+     10. A new genus of Pennsylvanian fish (Crossopterygii,
+     Coelacanthiformes) from Kansas. By Joan Echols. Pp. 475-501, 7
+     figures. October 25, 1963.
+
+     11. Observations on the Mississippi Kite in southwestern
+     Kansas. By Henry S. Fitch. Pp. 503-519. October 25, 1963.
+
+     12. Jaw musculature of the Mourning and White-winged doves. By
+     Robert L. Merz. Pp. 521-551, 22 figures. October 25, 1963.
+
+     13. Thoracic and coracoid arteries in two families of birds,
+     Columbidae and Hirundinidae. By Marion Anne Jenkinson. Pp.
+     553-573, 7 figures. March 2, 1964.
+
+     14. The breeding birds of Kansas. By Richard F. Johnston. Pp.
+     575-655, 10 figures. May 18, 1964. 75 cents.
+
+     15. The adductor muscles of the jaw in some primitive reptiles.
+     By Richard C. Fox. Pp. 657-680, 11 figures in text. May 18,
+     1964.
+
+     Index. Pp. 681-694.
+
+Vol. 13.
+
+     1. Five natural hybrid combinations in minnows (Cyprinidae). By
+     Frank B. Cross and W. L. Minckley. Pp. 1-18. June 1, 1960.
+
+     2. A distributional study of the amphibians of the Isthmus of
+     Tehuantepec, México. By William E. Duellman. Pp. 19-72, plates
+     1-8, 3 figures in text. August 16, 1960. 50 cents.
+
+     3. A new subspecies of the slider turtle (Pseudemys scripta)
+     from Coahuila, México. By John M. Legler. Pp. 73-84, plates
+     9-12, 3 figures in text. August 16, 1960.
+
+     *4. Autecology of the copperhead. By Henry S. Fitch. Pp.
+     85-288, plates 13-20, 26 figures in text. November 30, 1960.
+
+     5. Occurrence of the garter snake, Thamnophis sirtalis, in the
+     Great Plains and Rocky Mountains. By Henry S. Fitch and T. Paul
+     Maslin. Pp. 289-308, 4 figures in text. February 10, 1961.
+
+     6. Fishes of the Wakarusa River in Kansas. By James E. Deacon
+     and Artie L. Metcalf. Pp. 309-322, 1 figure in text. February
+     10, 1961.
+
+     7. Geographic variation in the North American cyprinid fish,
+     Hybopsis gracilis. By Leonard J. Olund and Frank B. Cross. Pp.
+     323-348, plates 21-24, 2 figures in text. February 10, 1961.
+
+     8. Descriptions of two species of frogs, genus Ptychohyla;
+     studies of American hylid frogs, V. By William E. Duellman. Pp.
+     349-357, plate 25, 2 figures in text. April 27, 1961.
+
+     9. Fish populations, following a drought, in the Neosho and
+     Marais des Cygnes rivers of Kansas. By James Everett Deacon.
+     Pp. 359-427, plates 26-30, 3 figures. August 11, 1961. 75
+     cents.
+
+     10. Recent soft-shelled turtles of North America (family
+     Trionychidae). By Robert G. Webb. Pp. 429-611, plates 31-54, 24
+     figures in text. February 16, 1962. $2.00.
+
+     Index. Pp. 613-624.
+
+Vol. 14.
+
+     1. Neotropical bats from western México. By Sydney Anderson.
+     Pp. 1-8. October 24, 1960.
+
+     2. Geographic variation in the harvest mouse, Reithrodontomys
+     megalotis, on the central Great Plains and in adjacent regions.
+     By J. Knox Jones, Jr., and B. Mursaloglu. Pp. 9-27, 1 figure in
+     text. July 24, 1961.
+
+     3. Mammals of Mesa Verde National Pork, Colorado. By Sydney
+     Anderson. Pp. 29-67, plates 1 and 2, 3 figures in text. July
+     24, 1961.
+
+     4. A new subspecies of the black myotis (bat) from eastern
+     Mexico. By E. Raymond Hall and Ticul Alvarez. Pp. 69-72, 1
+     figure in text. December 29, 1961.
+
+     5. North American yellow bats, "Dasypterus," and a list of the
+     named kinds of the genus Lasiurus Gray. By E. Raymond Hall and
+     J. Knox Jones, Jr. Pp. 73-98, 4 figures in text. December 29,
+     1961.
+
+     6. Natural history of the brush mouse (Peromyscus boylii) in
+     Kansas with description of a new subspecies. By Charles A.
+     Long. Pp. 99-111, 1 figure in text. December 29, 1961.
+
+     7. Taxonomic status of some mice of the Peromyscus boylii group
+     in eastern Mexico, with description of a new subspecies. By
+     Ticul Alvarez. Pp. 113-120, 1 figure in text. December 29,
+     1961.
+
+     8. A new subspecies of ground squirrel (Spermophilus spilosoma)
+     from Tamaulipas, Mexico. By Ticul Alvarez. Pp. 121-124. March
+     7, 1962.
+
+     9. Taxonomic status of the free-tailed bat, Tadarida yucatanica
+     Miller. By J. Knox Jones, Jr., and Ticul Alvarez. Pp. 125-133,
+     1 figure in text. March 7, 1962.
+
+     10. A new doglike carnivore, genus Cynaretus, from the
+     Clarendonian Pliocene, of Texas. By E. Raymond Hall and Walter
+     W. Dalquest. Pp. 135-138, 2 figures in text. April 30, 1962.
+
+     11. A new subspecies of wood rat (Neotoma) from northeastern
+     Mexico. By Ticul Alvarez. Pp. 139-143, April 30, 1962.
+
+     12. Noteworthy mammals from Sinaloa, Mexico. By J. Knox Jones,
+     Jr., Ticul Alvarez, and M. Raymond Lee. Pp. 145-159. 1 figure
+     in text. May 18, 1962.
+
+     13. A new bat (Myotis) from Mexico. By E. Raymond Hall. Pp.
+     161-164, 1 figure in text. May 21, 1962.
+
+     *14. The mammals of Veracruz. By E. Raymond Hall and Walter W.
+     Dalquest. Pp. 165-362, 2 figures. May 20, 1963. $2.00.
+
+     15. The recent mammals of Tamaulipas, México. By Ticul Alvarez.
+     Pp. 363-473, 5 figures in text. May 20, 1963. $1.00.
+
+     16. A new subspecies of the fruit-eating bat, Sturnira
+     ludovici, from western Mexico. By J. Knox Jones, Jr., and Gary
+     L. Phillips. Pp. 475-481, 1 figure in text. March 2, 1964.
+
+     17. Records of the fossil mammal Sinclairella, Family
+     Apatemyidae, from the Chadronian and Orellan. By William A.
+     Clemens. Pp. 483-491. 2 figures in text. March 2, 1964.
+
+     18. The mammals of Wyoming. By Charles A. Long. Pp. 493-758, 82
+     figs. July 6, 1965. $3.00.
+
+     Index. Pp. 759-784.
+
+Vol. 15.
+
+     1. The amphibians and reptiles of Michoacán, México. By William
+     E. Duellman. Pp. 1-148, plates 1-6, 11 figures in text.
+     December 20, 1961. $1.50.
+
+     2. Some reptiles and amphibians from Korea. By Robert G. Webb,
+     J. Knox Jones, Jr., and George W. Byers. Pp. 149-173. January
+     31, 1962.
+
+     3. A new species of frog (Genus Tomodactylus) from western
+     México. By Robert G. Webb. Pp. 175-181, 1 figure in text. March
+     7, 1962. 4. Type specimens of amphibians and reptiles in the
+     Museum of Natural History, the University of Kansas. By William
+     E. Duellman and Barbara Berg. Pp. 183-204. October 26, 1962.
+
+     5. Amphibians and Reptiles of the Rainforests of Southern El
+     Petén, Guatemala. By William E. Duellman. Pp. 205-249, plates
+     7-10, 6 figures in text. October 4, 1963.
+
+     6. A revision of snakes of the genus Conophis (Family
+     Colubridae, from Middle America). By John Wellman. Pp. 251-295,
+     9 figures in text. October 4, 1963.
+
+     7. A review of the Middle American tree frogs of the genus
+     Ptychohyla. By William E. Duellman. Pp. 297-349, plates 11-18,
+     7 figures in text. October 18, 1963. 50 cents.
+
+     *8. Natural history of the racer Coluber constrictor. By Henry
+     S. Fitch. Pp. 351-468, plates 19-22, 20 figures in text.
+     December 30, 1963. $1.00.
+
+     9. A review of the frogs of the Hyla bistincta group. By
+     William E. Duellman. Pp. 469-491, 4 figures in text. March 2,
+     1964.
+
+     10. An ecological study of the garter snake, Thamnophis
+     sirtalis. By Henry S. Fitch. Pp. 493-564, plates 23-25, 14
+     figures in text. May 17, 1965.
+
+     11. Breeding cycle in the ground skink, Lygosoma laterale. By
+     Henry S. Fitch and Harry W. Greene. Pp. 565-575, 3 figures in
+     text. May 17, 1965.
+
+     12. Amphibians and reptiles from the Yucatan Peninsula, México.
+     By William E. Duellman. Pp. 577-614, 1 figure in text. June 22,
+     1965.
+
+     13. A new species of turtle, Genus Kinosternon, from Central
+     America, by John M. Legler. Pp. 615-625, pls. 26-28, 2 figures
+     in text. July 20, 1965.
+
+     14. A biogeographic account of the herpetofauna of Michoacán,
+     México. By William E. Duellman. Pp. 627-709, pls. 29-36, 5
+     figures in text. December 30, 1965.
+
+     15. Amphibians and reptiles of Mesa Verde National Park,
+     Colorado. By Charles L. Douglas. Pp. 711-744, pls. 37, 38, 6
+     figures in text. March 7, 1966.
+
+     Index. Pp. 745-770.
+
+Vol. 16.
+
+     1. Distribution and taxonomy of Mammals of Nebraska. By J. Knox
+     Jones, Jr. Pp. 1-356, pls. 1-4, 82 figures in text. October 1,
+     1964. $3.50.
+
+     2. Synopsis of the lagomorphs and rodents of Korea. By J. Knox
+     Jones, Jr., and David H. Johnson. Pp. 357-407. February 12,
+     1965.
+
+     3. Mammals from Isla Cozumel, Mexico, with description of a new
+     species of harvest mouse. By J. Knox Jones, Jr., and Timothy E.
+     Lawlor. Pp. 409-419, 1 figure in text. April 13, 1965.
+
+     4. The Yucatan deer mouse, Peromyscus yucatanicus. By Timothy
+     E. Lawlor. Pp. 421-438, 2 figures in text. July 20, 1965.
+
+     5. Bats from Guatemala. By J. Knox Jones, Jr. Pp. 439-472.
+     April 18, 1966.
+
+     More numbers will appear in volume 16.
+
+Vol. 17.
+
+     1. Localities of fossil vertebrates obtained from the Niobrara
+     Formation (Cretaceous) of Kansas. By David Bardack. Pp. 1-14.
+     January 22, 1965.
+
+     2. Chorda tympani branch of the facial nerve in the middle ear
+     of tetrapods. By Richard C. Fox. Pp. 15-21, May 22, 1965.
+
+     3. Fishes of the Kansas River System in relation to
+     zoogeography of the Great Plains. By Artie L. Metcalf. Pp.
+     23-189, 4 figures in text, 51 maps. March 24, 1966.
+
+     4. Factors affecting growth and reproduction of channel
+     catfish, Ictalurus punctatus. By Bill A. Simco and Frank B.
+     Cross. Pp. 191-256, 13 figures in text. June 6, 1966.
+
+     5. A new species of fringe-limbed tree frog, genus Hyla, from
+     Darién, Panamá. By William E. Duellman. Pp. 257-262, 1 figure
+     in text. June 17, 1966.
+
+     6. Taxonomic notes on some Mexican and Central American hylid
+     frogs. By William E. Duellman. Pp. 263-279. June 17, 1966.
+
+     7. Neotropical hylid frogs, genus Smilisca. By William E.
+     Duellman and Linda Trueb. Pp. 281-375, pls. 1-12, 17 figures in
+     text. July 14, 1966.
+
+     8. Birds from North Borneo. By Max C. Thompson. Pp. 377-433, 1
+     figure in text. October 27, 1966.
+
+     9. Natural history of cottonmouth moccasin, Agkistrodon
+     piscivorus (Reptilia). By Ray D. Burkett. Pp. 435-491, 7
+     figures in text. October 27, 1966.
+
+     More numbers will appear in volume 17.
+
+
+
+
+
+End of the Project Gutenberg EBook of Natural History of Cottonmouth
+Moccasin, Agkistrodon piscovorus (Reptilia), by Ray D. Burkett
+
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+<pre>
+
+The Project Gutenberg EBook of Natural History of Cottonmouth Moccasin,
+Agkistrodon piscovorus (Reptilia), by Ray D. Burkett
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Natural History of Cottonmouth Moccasin, Agkistrodon piscovorus (Reptilia)
+
+Author: Ray D. Burkett
+
+Release Date: December 15, 2011 [EBook #38308]
+
+Language: English
+
+Character set encoding: UTF-8
+
+*** START OF THIS PROJECT GUTENBERG EBOOK NATURAL HISTORY OF ***
+
+
+
+
+Produced by Chris Curnow, Joseph Cooper and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+</pre>
+
+
+<h2><img src="images/bar_double.png" alt="double bar" height="15" width="100%" /></h2>
+<div class="smcap">
+    <h2><span class="smcap">University of Kansas Publications</span><br />
+        <span class="smcap">Museum of Natural History</span></h2>
+</div>
+<h2>Vol. 17, No. 9, pp. 435-491, 7 figures in text</h2>
+<div class="c7">
+    <h2><img src="images/bar_single.png" title="bar" alt="bar" height="15" width="28%" />&nbsp;&nbsp;October 27, 1966&nbsp;&nbsp;<img src="images/bar_single.png" title="bar" alt="bar" height="15" width="28%" /></h2>
+</div>
+<h1>Natural History of Cottonmouth Moccasin,</h1>
+<h1>Agkistrodon piscivorus (Reptilia)</h1>
+<h3>BY</h3>
+<h3>RAY D. BURKETT</h3>
+<h2> <span class="smcap">University of Kansas</span><br />
+    <span class="smcap">Lawrence<br />
+    </span>1966<br />
+</h2>
+<hr class="chap" />
+<p><span class="pagenum"><a name="Page_436" id="Page_436">[436]</a></span></p>
+<div class="c7">
+    <h3> <span class="smcap">University of Kansas Publications, Museum of Natural History</span><br />
+        <br />
+        Editors: E. Raymond Hall, Chairman, Henry S. Fitch,<br />
+        Frank B. Cross</h3>
+    <h4>Vol. 17, No. 9, pp. 435-491, 7 figures in text<br />
+        Published
+        October 27, 1966 </h4>
+    <h3> <b> <span class="smcap">University of Kansas</span><br />
+        <span style="font-weight: 400">Lawrence</span>, <span style="font-weight: 400">Kansas</span></b><br />
+    </h3>
+    <h5>PRINTED BY<br />
+        ROBERT R. (BOB) SANDERS, STATE PRINTER<br />
+        TOPEKA, KANSAS<br />
+        1966<br />
+        <br />
+        31-4629</h5>
+</div>
+<p><span class="pagenum"><a name="Page_437" id="Page_437">[437]</a></span></p>
+<hr class="chap" />
+<h2><a name="Natural_History_of_Cottonmouth_Moccasin" id="Natural_History_of_Cottonmouth_Moccasin"></a>Natural History of Cottonmouth Moccasin,<br />
+    Agkistrodon piscivorus (Reptilia)</h2>
+<h4>BY<br />
+    RAY D. BURKETT</h4>
+<hr class="chap" />
+<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2>
+<div class="c7">
+    <table summary="contents" cellpadding="3" cellspacing="0" width="80%">
+        <tbody>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td align="right"><small>PAGE</small></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Introduction</span></td>
+                <td align="right"><a href="#Page_439">439</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Acknowledgments</span></td>
+                <td align="right"><a href="#Page_440">440</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Systematic Relationships and Distribution</span></td>
+                <td align="right"><a href="#Page_441">441</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Description</span></td>
+                <td align="right"><a href="#Page_444">444</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Color and Pattern</td>
+                <td align="right"><a href="#Page_444">444</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Scutellation</td>
+                <td align="right"><a href="#Page_444">444</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Dentition</td>
+                <td align="right"><a href="#Page_449">449</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Habitat and Limiting Factors</span></td>
+                <td align="right"><a href="#Page_450">450</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Reproduction</span></td>
+                <td align="right"><a href="#Page_452">452</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Courtship and Mating</td>
+                <td align="right"><a href="#Page_452">452</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Reproductive Cycles</td>
+                <td align="right"><a href="#Page_452">452</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Embryonic Development</td>
+                <td align="right"><a href="#Page_454">454</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Birth of Young</td>
+                <td align="right"><a href="#Page_454">454</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Number of Young per Litter</td>
+                <td align="right"><a href="#Page_454">454</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Population Composition</td>
+                <td align="right"><a href="#Page_455">455</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Reproductive Potential</td>
+                <td align="right"><a href="#Page_455">455</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Growth and Development</span></td>
+                <td align="right"><a href="#Page_456">456</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Size at Birth and Early Growth</td>
+                <td align="right"><a href="#Page_456">456</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">The Umbilical Scar</td>
+                <td align="right"><a href="#Page_457">457</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Later Growth and Bodily Proportions</td>
+                <td align="right"><a href="#Page_457">457</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Shedding</span></td>
+                <td align="right"><a href="#Page_459">459</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">The Shedding Operation</td>
+                <td align="right"><a href="#Page_459">459</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Frequency of Shedding</td>
+                <td align="right"><a href="#Page_460">460</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Food Habits</span></td>
+                <td align="right"><a href="#Page_461">461</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Methods of Obtaining Prey</td>
+                <td align="right"><a href="#Page_461">461</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Food and Food Preferences</td>
+                <td align="right"><a href="#Page_462">462</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Mortality Factors</span></td>
+                <td align="right"><a href="#Page_465">465</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Natural Enemies and Predators</td>
+                <td align="right"><a href="#Page_465">465</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Parasites and Diseases</td>
+                <td align="right"><a href="#Page_465">465</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Miscellaneous Causes of Death</td>
+                <td align="right"><a href="#Page_466">466</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Behavior</span></td>
+                <td align="right"><a href="#Page_466">466</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Annual and Diel Cycles of Activity</td>
+                <td align="right"><a href="#Page_466">466</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Basking</td>
+                <td align="right"><a href="#Page_469">469</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Coiling</td>
+                <td align="right"><a href="#Page_469">469</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Locomotion</td>
+                <td align="right"><a href="#Page_470">470</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Disposition</td>
+                <td align="right"><a href="#Page_470">470</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Defense and Escape</td>
+                <td align="right"><a href="#Page_471">471</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&quot;Head Bobbing&quot;</td>
+                <td align="right"><a href="#Page_471">471</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Combat Dance</td>
+                <td align="right"><a href="#Page_472">472</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">The Venom</span></td>
+                <td align="right"><a href="#Page_473">473</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Properties of the Venom</td>
+                <td align="right"><a href="#Page_473">473</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Venom Yield and Toxicity</td>
+                <td align="right"><a href="#Page_473">473</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Susceptibility of Snakes</td>
+                <td align="right"><a href="#Page_475">475</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">The Bite</span></td>
+                <td align="right"><a href="#Page_476">476</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Effects of the Bite</td>
+                <td align="right"><a href="#Page_476">476</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Treatment</td>
+                <td align="right"><a href="#Page_477">477</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Case History of a Bite</td>
+                <td align="right"><a href="#Page_479">479</a></td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">Snakebite in the United States</td>
+                <td align="right"><a href="#Page_480">480</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Summary</span></td>
+                <td align="right"><a href="#Page_480">480</a></td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left"><span class="smcap">Literature Cited</span></td>
+                <td align="right"><a href="#Page_485">485</a></td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p><span class="pagenum"><a name="Page_439" id="Page_439">[439]</a></span></p>
+<hr class="chap" />
+<h2>INTRODUCTION</h2>
+<p>Objectives of the study here reported on were to: (1) learn as
+    much as possible concerning the natural history and economic
+    importance of the cottonmouth; (2) determine what factors limit
+    its geographic distribution; (3) determine the role of the cottonmouth
+    in its ecological community; and (4) compare the cottonmouth's
+    life history with that of other crotalid snakes, especially the
+    kinds that are most closely related to it.</p>
+<p>Twenty-five live cottonmouths were kept in the laboratory for
+    the purpose of studying behavior and fang shedding and for comparison
+    of measurements with those of preserved specimens. Live
+    snakes were obtained in Brazoria and Nacogdoches counties, Texas,
+    from Hermann Park Zoo, Houston, Texas, and from the late Paul
+    Anderson of Independence, Missouri. Preserved western cottonmouths
+    were examined for the purpose of determining variation,
+    distribution, food habits, body proportions, embryonic development,
+    and reproductive cycles. The cottonmouths examined include:
+    221 from Texas; 33 from Arkansas; 22 from Louisiana; 2
+    from Illinois; and 1 each from Kansas, Mississippi, and Oklahoma.</p>
+<p>In the preparation of this report I have examined all available
+    literature pertaining to the cottonmouth and have drawn from
+    these sources for comparative or additional material. Some of the
+    more noteworthy contributions to knowledge of the cottonmouth
+    are the general accounts of the life history by Allen and Swindell
+    (1948), Barbour (1956), and Wright and Wright (1957); the publications
+    by Gloyd and Conant (1943) concerning taxonomy;
+    Klimstra (1959) concerning food habits; and Allen (1937), Parrish
+    and Pollard (1959), Swanson (1946), and Wolff and Githens
+    (1939b) concerning the venom. Numerous other publications,
+    although brief, contain worthwhile contributions. Also of special
+    interest as a source of material for comparison of cottonmouths with
+    other crotalids are the works of Fitch (1960) on the copperhead and
+    of Klauber (1956) on the rattlesnakes.</p>
+<p>The cottonmouth has been well known for nearly 200 years.
+    Wright and Wright (1957) listed the following vernacular names
+    that are applied to the cottonmouth: black moccasin, black snake,
+    blunt-tail moccasin, congo, copperhead, cottonmouth water moccasin,
+    cotton-mouthed snake, gapper, highland moccasin, lowland
+    moccasin, mangrove rattler, moccasin, North American cottonmouth
+    snake, North American water moccasin, North American
+    water viper, pilot, rusty moccasin, salt-water rattler, stubtail, stump <span class="pagenum"><a name="Page_440" id="Page_440">[440]</a></span> (-tail) moccasin, stump-tail viper, swamp lion, Texas Moccasin,
+    trapjaw, Troost's moccasin, true horn snake, true water moccasin,
+    viper, water mokeson, water pilot, water rattlesnake, and water
+    viper.</p>
+<p>Some of the names listed above are based upon superstition and
+    folklore prevailing in pioneer times, and others are based upon the
+    behavior or appearance of the snake at various ages. Names like
+    &quot;stump-tail moccasin&quot; are derived from the appearance of females
+    which have short tails or snakes that have lost part of the tail.
+    Names like &quot;gapper&quot; and &quot;trapjaw&quot; came to be applied because
+    of the habit of the snake's lying with its mouth open when approached.
+    The name &quot;cottonmouth&quot; also was derived from this
+    behavior, although the lining of the mouth is whitish in most other
+    snakes. The term &quot;rattlesnake&quot; may have come from the fact that
+    the cottonmouth vibrates its tail vigorously when nervous as do
+    many other snakes, or it may have been confused with rattlesnakes.
+    Because of the general public's fear of snakes and their reluctance
+    to learn to discriminate between the poisonous and harmless species,
+    numerous kinds of snakes seen in or near water have been called
+    moccasins. The general appearance, pugnacious behavior, and
+    whitish mouth of water-snakes (<i>Natrix</i>) have earned them a bad
+    reputation. In fact, a great majority of the &quot;cottonmouths&quot; reported
+    in many areas are found to be water-snakes.</p>
+<p>The cottonmouth is economically important mainly because of
+    the injurious or fatal effects of its bite and the psychological effect
+    that its actual or suspected presence has upon many persons. The
+    species eats a wide variety of prey items and helps to prevent overabundance
+    of certain kinds of organisms. The venom has been
+    used in the therapeutic treatment of blood clots owing to its anticoagulant
+    properties (Didisheim and Lewis, 1956). It also is employed
+    in the treatment of haemorrhagic conditions and rheumatoid
+    arthritis, as well as in the production of antivenin (Allen and
+    Swindell, <i>op cit.</i>:13). None of these uses of venom has become
+    widely accepted, and its value is questionable.</p>
+<hr class="chap" />
+<h2>ACKNOWLEDGMENTS</h2>
+<p>For guidance in the course of my study, I am especially indebted to Professor
+    Henry S. Fitch. For suggestions concerning the preparation of the
+    manuscript, I thank Professor E. Raymond Hall. I am grateful to my wife,
+    Janis, for her invaluable assistance and for typing the manuscript.</p>
+<p>For use of specimens in their care, I thank Professors William E. Duellman,
+    University of Kansas; Robert L. Packard, formerly of Stephen F. Austin State
+    College; W. Frank Blair, University of Texas; and William B. Davis and</p>
+<p><span class="pagenum"><a name="Page_441" id="Page_441">[441]</a></span></p>
+<p>Richard J. Baldauf, Texas Agricultural and Mechanical College. Mr. John
+    E. Werler of the Hermann Park Zoo, Houston, Texas, contributed live individuals;
+    Mr. Richard S. Funk contributed information on the birth of a brood
+    of cottonmouths; and Dr. Henry M. Parrish contributed information on the
+    incidence of snakebite. To numerous other persons at leading museums
+    throughout the United States for information on the cottonmouths in their
+    collections, to all who helped with the field work in various ways, and to
+    others at the University of Kansas for their help and suggestions I am grateful.</p>
+<hr class="chap" />
+<h2>SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION</h2>
+<p>Snakes of the genus <i>Agkistrodon</i> are relatively primitive members of the
+    Crotalidae, which is one of the most specialized families of snakes. A majority
+    of the pit-vipers are found in the Americas, but close relatives are found from
+    extreme southeastern Europe through temperate Asia to Japan (<i>A. halys</i>) and
+    southeastern Asia including Indonesia (<i>Agkistrodon</i> and <i>Trimeresurus</i>). Familial
+    characters include: vertical pupil of the eye; facial pit present between
+    the preoculars and loreal; scales usually keeled; short, rotatable maxilla bearing
+    a large hollow fang; toothless premaxilla; chiefly hematoxic venom; and undivided
+    anal plate.</p>
+<p>The genus <i>Agkistrodon</i> includes about nine species in the Old World and
+    three in North and Central America. Some of the primitive characters of the
+    genus are: head covered with nine enlarged shields or having the internasals
+    and prefrontals broken up into small scales; subcaudals on proximal part of
+    tail undivided; fangs relatively short; tail lacking rattles. In one species, <i>A.
+    rhodostoma</i>, the scales are smooth; and the female is oviparous and guards her
+    eggs until they hatch. Other species have keeled scales and are ovo-viviparous.</p>
+<p>There is little paleontological evidence illustrating evolution of the cottonmouth
+    or for that matter of crotalids in general. Brattstrom (1954) summarized
+    the current knowledge of fossil pit-vipers in North America. The few fossils
+    found of the cottonmouth are from Alacha, Brevard, Citrus, Levy, Pasco, and
+    Pinellas counties, Florida (Brattstrom, <i>op. cit.</i>:35; Auffenberg, 1963:202). All
+    are of late Pleistocene Age and well within the present geographic range of the
+    cottonmouth.</p>
+<p>Of crotalid genera only <i>Agkistrodon</i> occurs in both the Old World and the
+    New World, suggesting that this genus is relatively old. Schmidt (1946:
+    149-150) mentioned several other closely related groups of animals found in
+    both eastern Asia and eastern North America, including the reptilian genera: <i>Natrix</i>, <i>Opheodrys</i>, <i>Elaphe</i>, <i>Ophisaurus</i>, <i>Leiolopisma</i> (= <i>Lygosoma</i>), <i>Eumeces</i>, <i>Clemmys</i>, <i>Emmys</i>, and <i>Alligator</i>. Of the groups of animals now confined to
+    these two regions the most important are the cryptobranchid salamanders, the
+    genus <i>Alligator</i>, and the spoon-bills (<i>Psephurus</i> in China and <i>Polyodon</i> in the
+    Mississippi drainage). Fossil evidence for these groups indicates that existing
+    forms common to eastern Asia and eastern North America are remnants of a
+    late Cretaceous or early Tertiary Holarctic fauna which was forced southward
+    as the climate became gradually cooler to the north. &quot;Other clues suggest
+    that both <i>Agkistrodon</i> and <i>Trimeresurus</i> (<i>Bothrops</i>) moved from Asia to
+    America, one of these presumably giving rise to the rattlesnakes.&quot; (Darlington,
+    1957:228).</p>
+<p><span class="pagenum"><a name="Page_442" id="Page_442">[442]</a></span></p>
+<p>The named, American kinds of <i>Agkistrodon</i> currently are arranged as three
+    species: the copperhead, the cantil and the cottonmouth. The copperhead
+    (<i>A. contortrix</i>) is divided into four subspecies, all of which are terrestrial. This
+    species occurs from southern New England to eastern Kansas and along the
+    Atlantic and Gulf Coastal plains, exclusive of peninsular Florida and the delta
+    of the Mississippi River in Louisiana. It extends southwest from Kansas through
+    the Edwards Plateau of west-central Texas. Isolated populations occur in the
+    Chisos and Davis mountains of Trans-Pecos Texas. The cantil or Mexican
+    moccasin (<i>A. bilineatus</i>), probably the nearest relative of the cottonmouth
+    (<i>A. piscivorus</i>), is divisible into two subspecies and occupies a nearly complementary
+    range from Mexico south to Nicaragua. The cottonmouth occurs
+    throughout the coastal plains of the southeastern United States, usually at
+    altitudes of 500 feet or less. Two subspecies are recognized, the eastern <i>A. p.
+    piscivorus</i> and the western <i>A. p. leucostoma</i>. A revision of the genus is underway
+    by Professor Howard K. Gloyd.</p>
+<p>The basic pattern and various behavioral traits are common to all three
+    species. The young are more nearly alike in appearance than adults, the
+    copperhead and the cottonmouth being easily confused. Adults differ in
+    color, size, body proportions, habitat, and habits. In range and habitat preference
+    the cottonmouth more closely resembles the southern subspecies of
+    the copperhead, <i>A. c. contortrix</i>, which is usually found in lowlands, near
+    swamps and streams, but seldom in water.</p>
+<div class="figcenter" style="width: 600px;"> <img src="images/i_442.jpg" alt="Fig. 1. Geographic range of the cottonmouth" height="434" width="600" /> <span class="caption">Fig. 1.</span> </div>
+<p><span class="smcap">Fig. 1.</span> Geographic range of the cottonmouth, showing marginal and near-marginal
+    records, based largely upon maps by Gloyd and Conant (1943:165)
+    and Conant (1958:336) but including additional records. The more important
+    of these records (from east to west) are discussed in the following paragraphs.
+    Crosshatching indicates the area of intergradation between the eastern and
+    western subspecies. Old records, indicated by dates, and their sources are as
+    follows: 1850's and 1891&mdash;U. S. National Museum numbers 4263 and 32753
+    respectively; 1897&mdash;Hurter (1897); and 1895&mdash;Stejneger (1895:408).</p>
+<p><span class="pagenum"><a name="Page_443" id="Page_443">[443]</a></span></p>
+<p>The northernmost record for the eastern subspecies is in the Petersburg area,
+    Prince George County, Virginia (Anon., 1953:24). A sight record (Hickman,
+    1922:39) near Bristol, West Virginia, probably was based on a water-snake
+    (<i>Natrix</i> sp.), since the stream in which the snake was seen flows north into the
+    Ohio River rather than southeast through Virginia. In North Carolina the
+    most inland record is from the Neuse River, six to eight miles east of Raleigh
+    (Stejneger, 1895:408). Neill (1947:205) reported a population in the vicinity
+    of Dry Fork Creek on the boundary line of Wilkes and Oglethorpe counties,
+    Georgia. Distribution of cottonmouths in Florida is statewide, including the
+    Keys and other offshore islands.</p>
+<p>The ranges of the two subspecies, <i>piscivorus</i> and <i>leucostoma</i>, meet near the
+    eastern border of Mississippi. <i>A. p. piscivorus</i> has been reported from Tishomingo
+    County to the Gulf and east of the Loess Bluff area in central Mississippi,
+    and <i>A. p. leucostoma</i> has been reported from this area westward. A few
+    specimens from along the Coast indicate intergradation (Cook, 1962:33) between
+    the two subspecies.</p>
+<p>Barbour (1956:33) reported one specimen from Cypress Creek, in the Green
+    River drainage, Muhlenberg County, Kentucky, and stated that suitable habitat
+    can be found in several areas east of Kentucky Lake. Hence, cottonmouths
+    may have entered this area via the Ohio River. Stejneger (<i>loc. cit.</i>)
+    reported the species in the Wabash River at Mount Carmel, Wabash County,
+    Illinois, and mentioned a former occurrence at Vincennes, Knox County,
+    Indiana; but there are no recent records at these localities. Hurter (1897)
+    reported having seen cottonmouths in Illinois, opposite St. Louis; Smith (1961:265)
+    believes that this and a population in Monroe County, Illinois, are
+    isolated relicts, since no specimens have been found within 50 miles to the
+    south of Monroe County. The specimens reported by Anderson (1941:178;
+    1945:274) near Chillicothe (three miles southwest and seven miles northwest,
+    respectively), Livingston County, Missouri, also are thought to represent a relict
+    population. Hall and Smith (1947:453) reported one specimen from Jasper
+    County, Missouri, in the Spring River which flows through extreme southeastern
+    Kansas and into Oklahoma and another in the Neosho River at Chetopa, Kansas.
+    Both of these specimens were taken after a flood, and no additional
+    specimens have been taken in this region. Nevertheless, sufficient habitat is
+    probably available along the Neosho and Verdigris rivers in the southeastern
+    part of Kansas.</p>
+<p>In Texas the cottonmouth has penetrated marginal habitat perhaps farther
+    than anywhere else in its range. Formerly it was thought to be limited to the
+    country east of the Balcones Escarpment (Smith and Buechner, 1947:8), but
+    semiarid areas of the state have been invaded primarily via the Colorado and
+    Brazos River systems up to altitudes of 2300 feet. Two additional specimens
+    are said to have been collected along the Rio Grande. Dr. Howard K. Gloyd
+    (<i>in litt.</i>) stated that the specimen reported from Eagle Pass, Maverick County,
+    is believed to have been taken in the 1850's; and the one said to have come
+    from the mouth of the Devil's River is actually marked &quot;near Santa Rosa,
+    Cameron County, September 30, 1891.&quot; No additional specimens have been
+    taken in that area; and the range now probably extends no farther south than
+    Corpus Christi, Texas. Brown's (1903:554) knowledge of the extension of
+    the range of the cottonmouth west of longitude 98&deg; is probably based upon
+    the records along the Rio Grande reported in the nineteenth century.</p>
+<p>Three extensions of the known range in Texas are reported herein. One
+    specimen was captured by Mr. Harry Green (HWG 346) along the San Saba
+    River, 8.1 miles west of Menard, Menard County. The other two specimens
+    (KU 84375 and 84376) were taken by the late Paul Anderson one and one-half
+    miles north of Pecan Crossing, South Concho River, Tom Green County,
+    and one mile west of Mertzon, Irion County.</p>
+<p>In the hypsithermal period following Pleistocene glaciation, cottonmouths
+    gradually moved northward occupying areas beyond their present range. The
+    distributional records since the 1850's and the apparent relict populations now
+    in existence indicate that the range of this species has since receded.</p>
+<hr class="chap" />
+<p><span class="pagenum"><a name="Page_444" id="Page_444">[444]</a></span> </p>
+<h2>DESCRIPTION</h2>
+<h3>Color and Pattern</h3>
+<p>Color predominantly brown, ranging through pale reddish-brown or dark
+    reddish-brown, brownish-green, to almost black; 10 to 17 irregular dark brown
+    bands on paler brown ground color; young paler (some nearly salmon pink),
+    retaining a vivid pattern throughout first year; pattern of most individuals
+    nearly obliterated by third year; brilliance and dullness of predominant color
+    correlated with molting cycle (skin especially bright and shiny immediately
+    following shedding; tip of tail yellowish in juveniles; posterior part of venter
+    and tail uniformly black in some adult individuals, especially females; secondary
+    sexual differences in dorsal coloration, such as found in copperhead by Fitch
+    (1960:102), not noted.</p>
+<p>The eastern subspecies, <i>A. p. piscivorus</i>, has the more brilliant pattern in
+    which the centers of the dark cross-bands are invaded by the ground color.
+    The cross-bands are slightly constricted in the mid-line and may or may not be
+    bilaterally symmetrical. One-half of the cross-band may be displaced anteriorly
+    or posteriorly to a slight degree or may even be completely absent. From one
+    to several dark spots may be present within the cross-bands.</p>
+<p>The western subspecies, <i>A. p. leucostoma</i>, has a comparatively dull pattern
+    in which the ground color does not invade the center of the cross-bands. In
+    many instances the bands are outlined by white scales, as in the Mexican
+    moccasin (this character is not so prominent in <i>A. p. piscivorus</i> because of
+    the paler ground color). A large, dark blotch usually occurs at the base of
+    the cross-band and may completely cross the ventral scales. The characteristic
+    variations found in <i>piscivorus</i> are also present in <i>leucostoma</i>.</p>
+<p>The number of bands is often difficult to count because of the dark color
+    of some specimens. Gloyd and Conant (1943:168) reported averages of 12.5
+    (11 to 16) and 12.2 (10 to 16) in males and females, respectively, of <i>leucostoma</i> and ranges of 10 to 17 for males and 10 to 16 for females with averages
+    of 13 in both sexes of <i>piscivorus</i>. On 20 specimens of <i>leucostoma</i> from Texas
+    the average number of bands was 12.7 (11 to 15). If the number of bands
+    differed on the two sides of an animal, the total number of the two sides was
+    divided by two.</p>
+<blockquote>
+    <h3>Scutellation</h3>
+</blockquote>
+<p>The scutellation of the cottonmouth closely resembles that of the other
+    species of <i>Agkistrodon</i>. For example, the nine cephalic shields are characteristic
+    of most species of <i>Agkistrodon</i>, as well as most other primitive crotalids and
+    viperids, and most colubrids. Most individuals have an additional pair of large
+    scales behind the parietals.</p>
+<p>The numbers of postoculars, supralabials, and infralabials are variable. On
+    either side the postoculars (three in most specimens) are reduced to two in
+    some specimens. The supralabials (eight in most specimens) frequently vary
+    (usually on one side only) from seven to nine. The number of infralabials is
+    somewhat more variable than the number of supralabials, the usual number
+    being 11, but 10 is also common; 8, 9, and 12 are more rare (Table 1). In
+    102 snakes in which these characters were examined, four different combinations
+    of supralabials and seven combinations of infralabials were found. Both
+    characters together yielded 16 combinations, considering only the actual number
+    of scales and not taking into account the side of the head on which they
+    occurred (Table 2). The combinations found in a brood of seven young from
+    Houston, Texas, are shown in Table 3 to illustrate the variability of this character.
+    Gloyd and Conant (1943:168) found a variation of 6 to 11 (8) and 7
+    to 9 (8) supralabials and 8 to 13 (11) and 8 to 12 (10.4) infralabials in
+    samples of 301 <i>leucostoma</i> and 119 <i>piscivorus</i>, respectively (numbers in
+    parentheses represent average). Also of interest is the variability of the scales
+    themselves. In one instance a scale was found that had not completely divided.
+    In another specimen the last supralabial and last infralabial were one scale
+    that completely lined the angle of the jaw. Instances of one scale almost <span class="pagenum"><a name="Page_445" id="Page_445">[445]</a></span> crowding out another were common. In still other instances one or two
+    supralabials were divided horizontally into two scales. Individual variation
+    rather than geographical variation occurs in these characters.</p>
+<p style="text-align: center">&nbsp; </p>
+<p style="text-align: center"> TABLE 1.&mdash;Frequency of Occurrence of Various Numbers of Supralabial and<br />
+    Infralabial Scales in 102 Cottonmouths.</p>
+<div class="c7">
+    <table summary="scale frequency" style="border-width: 1px; border-bottom-style: solid;"
+ cellpadding="3" cellspacing="0" width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Number of scales</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Specimens having number on both sides</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Specimens having number on one side</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Total</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center">Percentage</td>
+            </tr>
+            <tr>
+                <td colspan="5" align="center">Supralabials</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-top-style: solid;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 11</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 24</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 35</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 25.2</td>
+            </tr>
+            <tr>
+                <td align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 64</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 27</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 91</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 65.5</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 9</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 0</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 2.2</td>
+            </tr>
+            <tr>
+                <td colspan="5" align="center"> Infralabials</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-top-style: solid;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 0</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 1.5</td>
+            </tr>
+            <tr>
+                <td align="center"> 9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 13</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9.6</td>
+            </tr>
+            <tr>
+                <td align="center"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 32</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 44</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 32.4</td>
+            </tr>
+            <tr>
+                <td align="center"> 11</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 53</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 22</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 75</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 55.1</td>
+            </tr>
+            <tr>
+                <td align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.5</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>&nbsp; </p>
+<p style="text-align: center"> TABLE 2.&mdash;Numbers of Supralabials and Infralabials of 102 Cottonmouths.</p>
+<div class="c7">
+    <table summary="number" cellpadding="3" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Number of<br />
+                    individuals</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Number of <br />
+                    supralabials</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Number of <br />
+                    infralabials</td>
+            </tr>
+            <tr>
+                <td align="center"> 37</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+            </tr>
+            <tr>
+                <td align="center"> 15</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10-11</td>
+            </tr>
+            <tr>
+                <td align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+            </tr>
+            <tr>
+                <td align="center"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10-11</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9-10</td>
+            </tr>
+            <tr>
+                <td align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+            </tr>
+            <tr>
+                <td align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9-10</td>
+            </tr>
+            <tr>
+                <td align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10-12</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8-9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8-9</td>
+            </tr>
+            <tr>
+                <td align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 8-9</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 10-11</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>The dorsal scales of cottonmouths are strongly keeled except that those of
+    the two lower scale-rows on each side are weakly keeled. Also they are
+    slightly larger than the others. Two apical pits are present on each dorsal
+    scale. The shape of the scales and number of scale rows vary depending upon
+    the position on the body. Scales on the neck are considerably smaller than
+    those elsewhere on the body and are arranged in two or three more rows than
+    those at mid-body. The skin in the region of the throat, neck, and fore-body is <span class="pagenum"><a name="Page_446" id="Page_446">[446]</a></span> especially elastic and allows the swallowing of large prey. Posteriorly from the
+    mid-body the scales decrease in size and become more angular, those on the
+    tail tending to be rhomboidal and wider than long. In the region of the anus
+    the number of scale rows diminishes rapidly, leaving only 12 to 14 rows at the
+    base of the tail and only three rows immediately ahead of the tail tip. The
+    tail ends in a spine composed of two scales: one scale covers the bottom, lower
+    parts of the sides, and tip of the spine; and a shorter dorsal scale covers the
+    top and upper parts of the sides of the basal two-thirds of the spine. The
+    spine of embryos and young cottonmouths is blunt, but is pointed in most
+    adults.</p>
+<p style="text-align: center">&nbsp; </p>
+<p style="text-align: center"> TABLE 3.&mdash;Variation in Numbers of Supralabials and Infralabials in a Brood<br />
+    of Seven Cottonmouths.</p>
+<div class="c7">
+    <table summary="variation" cellpadding="3" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Number of<br />
+                    individuals</td>
+                <td style="border-top-style: double; border-width: 4px 1px 1px; border-bottom-style: solid; border-left-style: solid;" align="center"> Number of<br />
+                    supralabials</td>
+                <td style="border-top-style: double; border-width: 4px 1px 1px; border-bottom-style: solid; border-left-style: solid;" align="center"> Number of<br />
+                    infralabials</td>
+            </tr>
+            <tr>
+                <td align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+            </tr>
+            <tr>
+                <td align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9-10</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8-9</td>
+            </tr>
+            <tr>
+                <td align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+            </tr>
+            <tr>
+                <td align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9-10</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 1</td>
+                <td style="border-width: 1px; border-bottom-style: solid; border-left-style: solid;" align="center"> 8-9</td>
+                <td style="border-width: 1px; border-bottom-style: solid; border-left-style: solid;" align="center"> 10</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p style="text-align: center">&nbsp; </p>
+<p style="text-align: center"> TABLE 4.&mdash;Analysis of Number of Scale Rows at Three Parts of the Body<br />
+    in 81 Cottonmouths.</p>
+<div class="c7">
+    <table summary="analysis" cellpadding="2" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" rowspan="2" align="center"> Number<br />
+                    of scales<br />
+                    per row</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" colspan="2" align="center"> Neck</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" colspan="2" align="center"> Mid-body</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" colspan="2" align="center">Anterior to anus</td>
+            </tr>
+            <tr>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Number of<br />
+                    individuals</td>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Percentage</td>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Number of<br />
+                    individuals</td>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Percentage</td>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Number of<br />
+                    individuals</td>
+                <td style="border-left-style: solid; border-left-width: 1px; border-right-width: 1px; border-bottom-style: solid; border-bottom-width: 1px;" align="center">Percentage</td>
+            </tr>
+            <tr>
+                <td align="center"> 29</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 28</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3.7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 27</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 52</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 64.2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 26</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 16</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 18.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 25</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9.9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 67</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 82.7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 24</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4.9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 23</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9.9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4.9</td>
+            </tr>
+            <tr>
+                <td align="center"> 22</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4.9</td>
+            </tr>
+            <tr>
+                <td align="center"> 21</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 68</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 84.0</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 6.2</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>The number of scale rows on the neck, at mid-body, and just anterior
+    to the anus is relatively constant at 27-25-21, respectively; but some individual
+    variation is evident (Table 4). Since the rows are diagonally arranged, it is
+    necessary in counting scales to proceed either anteriorly or posteriorly across
+    the back; or the row may be counted in either direction up to the center of the
+    back and then reversed on the other side of the snake. In order to count the
+    scale rows in a position where no scale reduction or addition was occurring
+    and to avoid as much error as possible, I counted from anterior to center and
+    back on the neck, in any direction at mid-body, and from posterior to center
+    and back near the anus. Because females generally are the larger in circumference
+    posteriorly, they could have more scale rows than males just anterior <span class="pagenum"><a name="Page_447" id="Page_447">[447]</a></span> to the anus. The few snakes having more than 21 scale rows in the posterior
+    region offer no conclusive evidence as to tendencies, but in both instances in
+    which this occurred the females outnumbered the males three to one. An
+    odd, rather than an even, number of scale rows occurs on most of the length
+    of the snakes examined, because there is a mid-dorsal row and scale rows tend
+    to be lost on both sides at about the same level. An example of scale reduction
+    of one snake was as follows:</p>
+<div class="c7">
+    <table summary="scales" style="border-collapse: collapse"
+width="100%" cellpadding="0">
+        <tr>
+            <td align="right" class="tdr"> 6 + 7 (13)</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"> 6 + 7 (96)</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> 27 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 25 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 24 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 23 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 22 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> 5 + 6 (13)</td>
+            <td align="right" class="tdr"> 5 + 6 (90)</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"> 7 + 8 (111)</td>
+            <td align="right" class="tdr"> 7 + 8 (114)</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"> 6 + 7 (122)</td>
+            <td align="right"
+ class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"> + 7, -5 (125)</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> 23 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 22 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 23 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 21 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 22 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> -6 (118)</td>
+            <td align="right" class="tdr"> + 6 (119)</td>
+            <td align="right" class="tdr"> 6 + 7 (121)</td>
+            <td align="right"
+ class="tdr"> + 6 (123)</td>
+            <td align="right" class="tdr">&nbsp;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> -6 (126)</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr"> 22 &mdash;&mdash;&mdash;&mdash;&mdash;</td>
+            <td align="right" class="tdr"> 21 (130).</td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+        </tr>
+        <tr>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr">&nbsp;</td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+            <td align="right" class="tdr"></td>
+        </tr>
+    </table>
+</div>
+<p>This scale reduction follows the method proposed by Dowling (1951b: 133)
+    in which the numbers on the mid-line represent the number of scale rows,
+    upper figures refer to the right side of the snake, and figures in parentheses indicate
+    the number of the ventral scale (counted from the anterior end of the
+    series), thus marking the position of the addition or reduction. Addition of
+    a row is shown by a plus sign and the number of the row, whereas reductions
+    are shown by a minus sign and the number of the row that is lost or by a
+    plus sign between the number of two rows that join. According to Dowling,
+    variation in number of dorsal scales characterizes the few genera and species
+    of snakes in which it has been studied. The time and difficulty involved in
+    ascertaining the number of scales explain why it has not been widely used in
+    classification.</p>
+<div class="figcenter" style="width: 500px;"> <img src="images/i_447.jpg" alt="Fig. 2. Number of ventral scales in 48 female and 34 male A. p. leucostoma." height="387" width="500" /> <span class="caption">Fig. 2. Number of ventral scales in 48 female and 34
+    male <i>A. p. leucostoma</i>. </span></div>
+<blockquote>
+    <p>Ventral scales on 34 males averaged 134.4 (128 to 139), and on 48 females
+        133.5 (128 to 137) (Fig. 2.). Barbour (1956:34) found an average of 135.3
+        ventral scales on 64 males and 44 females, and Gloyd and Conant (<i>loc. cit.</i>)
+        found an average of 134 for both males and females. The average for the
+        eastern cottonmouth obtained by Gloyd and Conant, however, was 137 ventrals
+        in both sexes. Some of my counts were made before I knew of the standard
+        system of counting ventrals proposed by Dowling (1951a:97-99), in which <span class="pagenum"><a name="Page_448" id="Page_448">[448]</a></span> the first ventral plate is defined as the most anterior one bordered on both
+        sides by the first row of dorsals. Therefore, some inconsistencies may exist in
+        my counts. Where differences occur, Dowling's method probably will indicate
+        the presence of an additional scale, since it appears to begin farther anteriorly
+        on the average, than I began counting.</p>
+</blockquote>
+<div class="figcenter" style="width: 500px;"> <img src="images/i_448.jpg" alt="Fig. 3. Number of caudal scales in 44 female and 34 male A. p. leucostoma." height="402" width="500" /> <span class="caption">Fig. 3. Number of caudal scales in 44 female and 34
+    male <i>A. p. leucostoma</i>.</span> </div>
+<p style="text-align: center">&nbsp; </p>
+<p style="text-align: center"> TABLE 5.&mdash;Caudal Scale Combinations in 95 Cottonmouths. U = Undivided;<br />
+    D = Divided.</p>
+<div class="c7">
+    <table summary="scales" cellpadding="3" cellspacing="0">
+        <tbody>
+            <tr>
+                <td rowspan="2"
+    style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;"
+    align="center" class="tdc"><p style="text-align: center">Number<br />
+                        of<br />
+                        samples</p></td>
+                <td colspan="17"
+    style="border-left-style: solid; border-left-width: 1px; border-top-style: double; border-top-width: 4px;"
+    align="center" class="tdc"> Number of scales</td>
+            </tr>
+            <tr>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc">U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc">U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc"> U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc">D</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc">U</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid; border-bottom-style: solid;"
+    align="center" class="tdc">D</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 25</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">13-35</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">10-32</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 11</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">12-33</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">14-28</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">16-39</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1-9</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">3-24</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 3-37</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1-21</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-5</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-29</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">14-30</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1-8</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-7</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-8</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">2-10</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">18-23</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1-2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">6-11</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">6-9</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1-17</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-8</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">13-22</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 4-16</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1-4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">18-21</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">11</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">10</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 13</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">4</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">13</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 17</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">3</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">7</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;"
+    align="center" class="tdc">&nbsp;</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 9</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">3</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;"
+    align="center" class="tdc">6</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>Analysis of caudal scales revealed sexual dimorphism. In the six specimens
+    from Tennessee, Blanchard (1922:16) found the same thing. Caudals averaged
+    45.4 (41 to 50) on 34 males and 42.6 (39 to 49) on 44 females (Fig. 3).
+    Barbour (<i>loc. cit.</i>) found an average of 45.7 (30 to 54) caudals in males and
+    43 (17 to 56) in females. Caudal scale counts by Gloyd and Conant (<i>loc.
+    cit.</i>) averaged 44 (38 to 49) in males and 42 (37 to 48) in females of <i>leucostoma</i>;
+    in <i>piscivorus</i> they averaged 48 (42 to 53) in males and 44 (41 to 49)
+    in females. Another seldom-mentioned, unusual characteristic of the caudal <span class="pagenum"><a name="Page_449" id="Page_449">[449]</a></span> scales of copperheads and cottonmouths is that some are single (usually those
+    at the base of the tail) and others divided (Table 5). To my knowledge, all
+    other species have either single or divided scales the entire length of the tail.
+    See Klauber (1941:73) and Fox (1948:252) concerning correlation of few
+    scales with warm environment.</p>
+<h3>Dentition</h3>
+<p>Cottonmouths, like other pit-vipers, have their teeth reduced in number
+    and have enlarged, highly specialized fangs. Small teeth occur on the palatine
+    and the pterygoid in the upper jaw and on the dentary in the lower jaw. The
+    dentary bone bears 17 curved teeth that decrease in size posteriorly. The
+    palatine bears five small, strongly curved teeth, and the pterygoid bears 16 to
+    18 strongly curved teeth decreasing in size posteriorly. The numbers of teeth
+    mentioned above in each instance refer to the number of sockets rather than
+    the actual number of teeth, because teeth are frequently shed, leaving some
+    of the sockets empty at any one time.</p>
+<p>The maxillary bone has two sockets side by side which bear the poison
+    fangs, usually one at a time. During the period shortly before a fang is to be
+    shed, however, its replacement becomes attached in the alternate socket; and
+    both fangs may be functional for a short time. The old fang then becomes
+    weakened at its base, eventually breaks off, and is swallowed. At any one
+    time four or five replacement fangs in various stages of development are found
+    in the gum behind the functional fang. These replacement fangs, which are
+    arranged in alternate rows, gradually enlarge as they move forward in their
+    development and, in juveniles, are generally slightly longer than the fangs that
+    they replace.</p>
+<p>In 1963 I examined the fangs of 14 cottonmouths at four- to seven-day intervals
+    for a period of six weeks. The fang-shedding cycle was found to be
+    highly irregular, with a double condition (on one or both sides) occurring one-third
+    of the time. Approximately the same proportion of double fangs was
+    found in preserved individuals. A replacement period of at least five days
+    was observed in one snake. One-half the cycle (from replacement on one side
+    to replacement on the other) varied from five to twenty days, indicating that
+    the cycles for each fang are independent of one another. Bogert (1943:324)
+    found that young rattlesnakes are born with functional fangs in the two inner
+    sockets. Nonsynchronous use of the sockets on opposite sides of the head in
+    rattlesnakes is a later development which results from accidents or other conditions
+    leading to a longer retention of the fang on one side than on the other
+    (Klauber, 1956:723). I found a double set of fangs in cottonmouths only
+    twice in the six-week period. A complete cycle was recorded in ten instances
+    in a period of 19 to 23 days and in two instances in 32 days. One cottonmouth
+    was examined periodically over a 34-day period by Allen and Swindell
+    (1948:12), but a complete fang-shedding cycle was not observed. Fitch
+    (1960:110) reported a 33-day cycle in copperheads; Klauber (1956:726)
+    estimated the normal active life of each fang of an adult rattlesnake to be
+    from six to ten weeks, but he made no observations to confirm his estimation.</p>
+<p>Fangs measured from the tip of the notch of the basal lumen to the end of
+    the fang vary from about 1.3 per cent of the snout-vent length in juveniles to
+    about 1.0 per cent in large adults (Table 6). The fangs are longer than those
+    of copperheads (Fitch, 1960:111). Klauber's (1956:736) figures on fang-lengths
+    in all species of rattlesnakes are percentages of total length rather than
+    of the snout-vent length. The fangs of various species of rattlesnakes range
+    from nearly the same proportionate length as those of cottonmouths to some
+    much longer.</p>
+<p>From patterns of bites of venomous snakes, Pope and Perkins (1944:333-335)
+    attempted to correlate number, size, and patterns of tooth marks with
+    size and generic identity of the snake responsible for the bite. Distance between
+    fangs is relatively constant for snakes of a particular size (Table 6) regardless
+    of genus, but the fangs of a cottonmouth are directed outward to
+    variable degrees, and puncture wounds could easily resemble those of a much
+    larger snake (Table 7). Also there is no direct relationship between size of <span class="pagenum"><a name="Page_450" id="Page_450">[450]</a></span> snake and toxicity or amount of venom injected. Consequently information of
+    this kind is of little or no value from a medical standpoint.</p>
+<p style="text-align: center">&nbsp; </p>
+<p style="text-align: center"> TABLE 6.&mdash;Correlation of Relative Fang-length and Distance Between Fangs<br />
+    at Base with Snout-vent Length of Cottonmouths.</p>
+<div class="c7">
+    <table style="border-collapse: collapse;" summary="fangs"
+ cellpadding="3" width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Snout-vent length<br />
+                    (millimeters)                    &nbsp;</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"><p style="text-align: center">Number
+                        in<br />
+                        sample</p></td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"><p style="text-align: center">Average<br />
+                        ratio of<br />
+                        fang-length<br />
+                        to<br />
+                        snout-vent<br />
+                        length<br />
+                        (percent)</p></td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"><p style="text-align: center">Number<br />
+                        in sample</p>
+                    <p>&nbsp;</p></td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Average<br />
+                    ratio of<br />
+                    distance<br />
+                    between<br />
+                    fangs to<br />
+                    snout-vent<br />
+                    length<br />
+                    (percent)</td>
+            </tr>
+            <tr>
+                <td align="center">200-299</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.33</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.57</td>
+            </tr>
+            <tr>
+                <td align="center">300-399</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.30</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.48</td>
+            </tr>
+            <tr>
+                <td align="center">400-499</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 13</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.21</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.21</td>
+            </tr>
+            <tr>
+                <td align="center">500-599</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.22</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.19</td>
+            </tr>
+            <tr>
+                <td align="center">600-699</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.17</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2.10</td>
+            </tr>
+            <tr>
+                <td align="center">700-799</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.07</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1.65</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center">800-899</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 1.00</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 2.00</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>&nbsp; </p>
+<p style="text-align: center"> TABLE 7.&mdash;Contrast in Measurements Between the Base of the Fangs and<br />
+    Between Fang Punctures of Nine Cottonmouths (in millimeters).</p>
+<div class="c7">
+    <table cellpadding="3" summary="contrast" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Distance between<br />
+                    base of fangs</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Distance between<br />
+                    fang punctures</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Snout-vent<br />
+                    length</td>
+            </tr>
+            <tr>
+                <td align="center"> 7.7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 13.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 400</td>
+            </tr>
+            <tr>
+                <td align="center"> 8.7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 14.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 575</td>
+            </tr>
+            <tr>
+                <td align="center"> 10.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 22.5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 526</td>
+            </tr>
+            <tr>
+                <td align="center"> 11.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 18.0-19.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 590</td>
+            </tr>
+            <tr>
+                <td align="center"> 12.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 18.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 793</td>
+            </tr>
+            <tr>
+                <td align="center"> 13.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 17.0, 20.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 558, 612</td>
+            </tr>
+            <tr>
+                <td align="center"> 15.5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 23.5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 800</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 16.0</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 24.0</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 800</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<hr class="chap" />
+<h2>HABITAT AND LIMITING FACTORS</h2>
+<p>Although usually associated with swamps and lowlands along river bottoms,
+    the cottonmouth lives in a variety of habitats ranging from salt marshes to cool,
+    clear streams and from sea level to an altitude of 2300 feet. Shaded, moist
+    areas either in or beside shallow waters are preferred, but cottonmouths occasionally
+    wander as far as a mile from water.</p>
+<p>In the pine-oak forests of Nacogdoches County in eastern Texas cottonmouths
+    and copperheads are probably the most abundant species of snakes.
+    Specimens have been collected near Nacogdoches in ponds, swamps, clear and
+    fast-running streams with rock bottoms, and sluggish muddy streams. On the
+    Stephen F. Austin Experimental Forest numerous cottonmouths live in a
+    swamp until around mid-July, when it becomes dry. A small stream west of <span class="pagenum"><a name="Page_451" id="Page_451">[451]</a></span> the swamp seems to be used as a migration route to and from the swamp.
+    Slightly more than a mile downstream cottonmouths are common in a bottomland
+    area. The ground is always moist and no undergrowth occurs; a few
+    small clear springs produce shallow trickles that run into a swamp. Cottonmouths
+    can often be found here, lying in or beside the small trickles.</p>
+<p>I have seen cottonmouths in various types of aquatic habitats in Brazoria
+    County. In most places in this area, cottonmouths are found in association
+    with one or more species of water-snakes (including <i>Natrix cyclopion</i>, <i>N.
+    erythrogaster</i>, <i>N. rhombifera</i>, and <i>N. confluens</i>), which greatly outnumber the
+    cottonmouth. Interspecific competition may be reduced somewhat by cottonmouths
+    sometimes feeding on water-snakes.</p>
+<p>The numerous statements in the literature concerning the habitat of the
+    cottonmouth can be summarized most easily by the following short quotations:</p>
+<blockquote>
+    <p><i>Agkistrodon piscivorus piscivorus</i>&mdash;&quot;Marshes and lakes; ponds and streams
+        with wooded shores; low country near water; roadside ponds; drainage ditches;
+        coastal 'banks'; keys; some Gulf coast islands; mangrove swamps.&quot; (Wright
+        and Wright, 1957:919.)</p>
+    <p><i>Agkistrodon piscivorus leucostoma</i>&mdash;&quot;Cypress, gum, river swamps; alluvial
+        swamps wooded or not wooded; water courses of the south such as rivers,
+        bayous, backwaters of small branches; hill streams in the north; ...
+        marshy places in prairies ... rice fields, bottomland pools; margins of
+        above habitats, pools, shallow lakes, swampy places, temporary flood lands.
+        ... In, under, or on fallen timber, in holes in banks, rocky bluffs, crayfish
+        burrows. In short it is very aquatic.&quot; (Wright and Wright, <i>op. cit.</i>:923.)</p>
+</blockquote>
+<p>Geographically cottonmouths differ somewhat in their ecological requirements,
+    but are basically much alike in most respects. The areas of greatest
+    abundance are those having 40 inches or more of annual rainfall. The northern
+    edge of the range has a mean temperature of approximately 38&deg; F. in January
+    in Virginia and 30&deg; F. in Missouri, although the lowest temperature reached
+    in these areas is more important as a limiting factor. The annual rainfall in
+    both Virginia and Missouri amounts to approximately 40 inches. Moisture,
+    as well as temperature, may play an important role in the northward distribution
+    of the species. The eastern cottonmouth seems to be less tolerant of low
+    temperatures than the western subspecies. Mean January temperatures equal
+    to those along the northern limits of the western cottonmouth's distribution
+    are reached in the vicinity of Connecticut, which is north of the geographic
+    range of the eastern subspecies.</p>
+<p>The depths to which cottonmouths penetrate into their dens may have a
+    limiting influence upon the geographic range, especially in the northern extremes.
+    Bailey (1948:215) discussed the possibility that populations of snakes
+    may be significantly depressed because of winter kill of individuals that &quot;hibernate&quot;
+    at shallow depths. He speculated also that the short growing season
+    does not allow enough time for the essentials of existence to be carried out,
+    and the prolonged period of inactivity overtaxes the energy reserve of the
+    species.</p>
+<p>Available food does not seem to be of much importance as a limiting factor,
+    for the cottonmouth is remarkably indiscriminate in its choice of prey, feeding
+    upon almost any vertebrate animal that happens to come within reach. Competition
+    for food, however, may play an important role.</p>
+<p><span class="pagenum"><a name="Page_452" id="Page_452">[452]</a></span></p>
+<hr class="chap" />
+<h2>REPRODUCTION</h2>
+<h3>Courtship and Mating</h3>
+<p>A review of available literature indicates no records of courtship of the
+    cottonmouth other than statements that breeding occurs in early spring. In
+    a close relative, the copperhead (see Fitch, 1960:159-160), mating occurs
+    almost any time in the season of activity but is mainly concentrated in the
+    few weeks after spring emergence, at about the time when females are ovulating.
+    Klauber (1956:692) concluded that along the southern border of the
+    United States rattlesnakes normally mate in spring soon after coming out of
+    their winter retreats; but farther north where broods are produced biennially,
+    the mating times may be more widely dispersed, and summer and fall matings
+    may even predominate.</p>
+<p>The only record of copulation in the cottonmouth was reported by Allen
+    and Swindell (1948:11), who observed a pair copulating for three hours on
+    October 19, 1946, at the Ross Allen Reptile Institute. Davis (1936:267-268)
+    stated that courtship in cottonmouths is violent and prolonged but did not
+    note any nervous, jerky motions or nudging of the female along her back and
+    sides as had been observed in other genera of snakes. Carr (1936:90) saw
+    a male cottonmouth seize a female in his mouth and hold her, but no courtship
+    followed.</p>
+<h3>Reproductive Cycles</h3>
+<p>Many persons have assumed that gestation periods in snakes are the intervals
+    between mating and parturition, and that mating and ovulation occur at approximately
+    the same time. However, retention of spermatozoa and delayed
+    fertilization indicate that copulation is not a stimulus for ovulation.</p>
+<p>A biennial reproductive cycle was found for the copperhead in Kansas
+    (Fitch, 1960:162), the prairie rattler in Wyoming (Rahn, 1942:239) and in
+    South Dakota (Klauber, 1956:688), the great basin rattler in Utah (Glissmeyer,
+    1951:24), and the western diamondback rattler in northwestern Texas (Tinkle,
+    1962:309). Klauber's (1956:687) belief that the reproductive cycle of rattlesnakes
+    varies with climate, being biennial in the north and annual in the
+    south, is supported by similar climatic variation in the reproductive cycle of
+    the European viper which was discussed by Vols&oslash;e (1944:18, 149).</p>
+<p>If data for a large number of females were arranged as are those in Table 8,
+    they might reveal whether the breeding cycle is annual or biennial. The figures
+    presented in Table 8 are misleading if viewed separately because of the small
+    number of individuals included in some of the size classes.</p>
+<p>The smallest reproductive female found measured 455 millimeters in snout-vent
+    length. Conant (1933:43) reported that a female raised in captivity
+    gave birth to two young at an age of two years and ten months. The size
+    classes represented by gravid females found by Barbour (1956:38) in Kentucky
+    indicate that breeding occurs at least by the third year.</p>
+<p>The ovaries of female cottonmouths examined revealed ova in various stages
+    of development. In individuals less than 300 millimeters in snout-vent length
+    the ovaries are almost completely undeveloped; in immature individuals from
+    300 to 450 millimeters in length the follicles are from one to two millimeters
+    in length; in post-post females follicles vary in size, the largest being about
+    seven millimeters. Reproductive females also contain follicles of various sizes. <span class="pagenum"><a name="Page_453" id="Page_453">[453]</a></span> One or two sets are less than three millimeters in length, and large ova that
+    soon are to be ovulated are present. Ovarian ova found in April ranged in
+    length from 23 to 35 millimeters. No embryonic development was observed
+    in most individuals until June or later.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 8.&mdash;Percentage of Gravid Females of <i>A. p. leucostoma</i> in
+    50 Millimeter Size Classes.</p>
+<div class="c7">
+    <table cellpadding="2" summary="gravid females" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Snout-vent<br />
+                    length</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Number of<br />
+                    gravid females</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Total number<br />
+                    in size class</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Percentage<br />
+                    gravid</td>
+            </tr>
+            <tr>
+                <td align="center">450-499</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 14</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 21.4</td>
+            </tr>
+            <tr>
+                <td align="center">500-549</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 17</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 41.2</td>
+            </tr>
+            <tr>
+                <td align="center">550-599</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 17</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 47.1</td>
+            </tr>
+            <tr>
+                <td align="center">600-649</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 71.4</td>
+            </tr>
+            <tr>
+                <td align="center">650-699</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 9</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 22.2</td>
+            </tr>
+            <tr>
+                <td align="center">700-749</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 66.7</td>
+            </tr>
+            <tr>
+                <td align="center">750-799</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 100.0</td>
+            </tr>
+            <tr>
+                <td align="center">850-899</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 100.0</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> Totals</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 29</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 69</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 42.0</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>Increase in length of testes appears to be correlated with length of the
+    individual rather than cyclic reproductive periods (Fig. 4).</p>
+<div class="figcenter" style="width: 500px;"> <img src="images/i_453.jpg" alt="Fig. 4. Length of testes in cottonmouths of various sizes" height="315" width="500" /> <span class="caption">Fig. 4. Length of testes in cottonmouths of various sizes <br />
+    (<span class="xlfont"> &middot;</span>&mdash;left; </span> <span class="lfont">&deg;</span><span class="caption">&mdash;right ). The right testis is always longer than
+    the left. </span></div>
+<p>The reproductive cycle in cottonmouths resembles that illustrated by Rahn
+    (<i>op. cit.</i>:237), in which the ovarian follicles of post-partum females begin to
+    enlarge in late summer and autumn, with ovulation occurring the following
+    spring. By means of retaining sperm successive broods possibly are produced
+    after only one mating. In captivity, at least, some females may not follow
+    this biennial cycle; Stanley Roth (M.S.), biology teacher in high school at
+    Lawrence, Kansas, had a female of <i>A. p. piscivorus</i>, from Florida, that produced
+    broods of 14 and 12 young in two consecutive years.</p>
+<p><span class="pagenum"><a name="Page_454" id="Page_454">[454]</a></span></p>
+<h3>Embryonic Development</h3>
+<p>After ova are fertilized a three and one-half to four-month period of development
+    begins which varies somewhat depending on the temperature. In
+    almost every instance the ova in the right uterus outnumber those in the left.
+    Embryos usually assume the serpentine form in the latter part of June and
+    are coiled in a counterclockwise spiral with the head on the outside of the
+    coil. At this time the head is relatively large and birdlike in appearance with
+    conspicuous protruding eyes. Sex is easily noted because the hemipenes of
+    males are everted. By late July scales are well developed and the embryo is
+    more snakelike in appearance, but pigmentation is still absent. By mid-August
+    the color and pattern are well developed, the egg tooth is present, the snake
+    shows a considerable increase in size over that of the previous month, and
+    much of the yolk has been consumed. Some females that contain well developed
+    embryos also contain eggs that fail to develop. Sizes of ova vary
+    irrespective of size of female and stage of embryonic development. Lengths
+    of ova ranged from 22 to 51 millimeters in May to 35 to 49 millimeters in
+    July and August. A two-yolked egg was found in one female.</p>
+<h3>Birth of Young</h3>
+<p>Accounts in the literature of 15 litters of cottonmouths fix the time of
+    birth as August and September. Conant (1933:43) reported the birth of a
+    litter in mid-July by a female that had been raised in captivity, and one female
+    that I had kept in captivity for two months gave birth to a litter between
+    October 19 and October 25. The conditions of captivity undoubtedly affected
+    the time of birth in both instances.</p>
+<p>Wharton (1960:125-126) reported the birth and behavior of a brood of
+    seven cottonmouths in Florida. I was given notes of a similar nature by
+    Richard S. Funk of Junction City, Kansas, on a brood of five cottonmouths.
+    The mother of the brood was caught in June, 1962, in Tarrant County, Texas,
+    by Richard E. Smith, and was 705 millimeters in snout-vent length. The first
+    young was found dead in an extended position a few inches from the fetal
+    membranes at 11:05 p.m. on August 22. The second young was born at
+    11:07 p.m. The intervals between the successive births were three, seven,
+    and four minutes; and time until the sac was ruptured in each instance was
+    six, five, eight, and 11 minutes. The time interval between the rupture of the
+    sac and emergence of each individual was 41, 92, 154, and 34 minutes. The
+    mother's actions in giving birth to the last four young were essentially as
+    described by Wharton (<i>loc. cit.</i>), except that the intervals between successive
+    births did not increase. Within one minute after rupturing the sac and while
+    its head was protruding, each of the four living young opened its mouth
+    widely from three to seven times, then took its first breath. Breaths for the
+    first three hours were steady at three or four per minute but then decreased
+    to two or three per minute. Pulse rate for the four averaged 38 per minute
+    while at rest but increased to 44 per minute after voluntarily crawling.</p>
+<h3>Number of Young per Litter</h3>
+<p>Records of from one to 16 young per litter have been reported (Ditmars,
+    1945:330; Clark, 1949:259), but the average is probably between six or seven.
+    Most accounts in the literature present information on number of ova or embryos <span class="pagenum"><a name="Page_455" id="Page_455">[455]</a></span> per female rather than the number of young. Size and age of the
+    mother (Table 9) influence the number of ova produced. Allen and Swindell
+    (1948:11) recorded three to 12 embryos in 31 cottonmouths varying in total
+    length from 26 to 44 inches. An average of 6.5 embryos per female was
+    found.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 9.&mdash;Number of Ova Produced by Fecund Cottonmouths.</p>
+<div class="c7">
+    <table cellpadding="2" summary="ova" cellspacing="0" width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Snout-vent length<br />
+                    in millimeters</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Number<br />
+                    in sample</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Number of ova,<br />
+                    average and extremes</td>
+            </tr>
+            <tr>
+                <td align="center"> 450-549</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4.1 (2 to 7)</td>
+            </tr>
+            <tr>
+                <td align="center"> 550-649</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4.9 (1 to 8)</td>
+            </tr>
+            <tr>
+                <td align="center"> 650-749</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6.3 (4 to 8)</td>
+            </tr>
+            <tr>
+                <td align="center"> 750-849</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 850-949</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 14</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>Mortality at birth has been recorded for almost every litter born in captivity
+    (see Allen and Swindell, <i>loc. cit.</i>; Conant, 1933:43; Wharton, 1960:125).
+    A female that I kept in captivity gave birth to seven young. Three never
+    ruptured their sacs, and another died soon after leaving the sac. The effects
+    of captivity on females may result in higher rates of deformity and mortality
+    in young than is common in nature. Klauber (1956:699-700) estimated that
+    the defects brought about by conditions of captivity on rattlesnakes eliminate
+    about three young per litter.</p>
+<h3>Population Composition</h3>
+<p>No investigator has yet analyzed the composition of a population of cottonmouths
+    according to age, sex and snout-vent length. Barbour (1956:35) did
+    sort 167 snakes into size classes, but did not determine sex ratio, size at sexual
+    maturity, reproductive cycles, or snout-vent length. He recorded total lengths
+    from which snout-vent lengths cannot be computed because of differential
+    growth rates and different bodily proportions of the two sexes. I judge from
+    my findings that he included immature individuals in his three smallest size
+    classes (45.5 per cent of the population). I found at least 32.5 per cent immature
+    individuals (Fig. 5) in my material, but it was not a natural population.</p>
+<p>The sex ratios of several small collections from natural populations varied,
+    and no conclusions could be drawn. Females comprised 53 per cent of the
+    specimens included in Fig. 5 and in a group of 48 embryos which represented
+    eight broods. That percentage may not be the percentage in a natural population
+    but is used in making assumptions because I lack better information.</p>
+<h3>Reproductive Potential</h3>
+<p>If data in Fig. 5 are representative of a natural population and if 61 per
+    cent of the females are sexually mature, the reproductive potential can be
+    estimated as follows: assuming a cohort of 1000 cottonmouths contains 530
+    females, 61 per cent of the females (323 individuals) probably are adults.
+    If 42 per cent of these females produce 6.5 young per female in any season
+    (Tables 8 and 9), 136 females will produce 884 young. But if 50 per cent <span class="pagenum"><a name="Page_456" id="Page_456">[456]</a></span> of the adult females are reproductive (as would be assumed if reproduction
+    is biennial), 1050 young will be produced. Actually the number of young
+    required per year to sustain a population is unknown, because mortality rates
+    at any age are unknown.</p>
+<div class="figcenter" style="width: 500px;"> <img src="images/i_456.jpg" alt="Fig. 5. Composition of a group of cottonmouths" height="433" width="500" /> <span class="caption">Fig. 5. Composition of a group of cottonmouths examined in this
+    study. Individuals less than 450 millimeters in snout-vent length
+    are considered as immature. Specimens from 200 to 249 millimeters
+    in length are included in the 200-millimeter class, <i>etc.</i></span> </div>
+<hr class="chap" />
+<h2>GROWTH AND DEVELOPMENT</h2>
+<h3>Size at Birth and Early Growth</h3>
+<p>Size at birth depends on the health of the mother. According to Fitch
+    (1960:182), many litters of copperheads born in captivity are stunted. Seven
+    young cottonmouths (two males and five females) born in captivity were each
+    185 millimeters in snout-vent length and 40 millimeters in tail length. Weights
+    of the three living young were 10.0, 10.1, and 11.1 grams. Another litter of
+    five young measured by Richard S. Funk were larger, and differences in the
+    proportions of the tail length and snout-vent length suggest the sexual dimorphism
+    found in larger individuals. However, sex of these young snakes
+    was not recorded. Snout-vent length and tail length in millimeters were 232,
+    41; 243, 47; 229, 40; 240, 48; and 225, 40 in the order of their birth. These
+    snakes are considerably smaller than the nine young of <i>A. p. piscivorus</i> reported
+    by Wharton (1960:127) that averaged 338 millimeters total length and 28.7
+    grams. The yolk of one young <i>piscivorus</i> was 11.7 per cent of the total weight. <span class="pagenum"><a name="Page_457" id="Page_457">[457]</a></span> Yolk is used up in about two weeks if its rate of utilization resembles that of
+    the copperhead as reported by Gloyd (1934:600).</p>
+<p>Early rates of growth of three living young are shown in Table 10. On
+    the 56th day after birth, each was fed one minnow less than two inches long.
+    Between the 80th and 120th days three additional small minnows were fed
+    to each snake. Young cottonmouths increase nearly 50 millimeters in length
+    by the first spring if they inhabit warm areas and feed in autumn or winter.</p>
+<p>Variation in size of newborn cottonmouths may be less in nature than in
+    captivity. Average size at birth can be determined accurately by the size of
+    young captured in early spring, at least in northern parts of the range where
+    winter feeding and growth do not occur at all or are negligible. Total lengths
+    of 19 juveniles thought by Barbour (1956:38) to be seven to eight months old
+    do not differ markedly from lengths of the five newly-born young measured by
+    Funk.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 10.&mdash;Rate of Growth of Three Young Cottonmouths.</p>
+<div class="c7">
+    <table cellpadding="2" summary="growth rate" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td rowspan="2" style="border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Age<br />
+                    in days</td>
+                <td colspan="3" style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Snout-vent length / tail length&mdash;weight in grams</td>
+            </tr>
+            <tr>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> Female No. 1</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> Female No. 2</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> Male</td>
+            </tr>
+            <tr>
+                <td align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp; 185/40&mdash;11.1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 185/40&mdash;10.1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 185/40&mdash;10.0</td>
+            </tr>
+            <tr>
+                <td align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp; 192/40&mdash;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 190/40&mdash;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 189/40&mdash;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center"> 22</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp; 195/40&mdash;10.3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 200/41.5&mdash;10.6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 197/40&mdash;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </td>
+            </tr>
+            <tr>
+                <td align="center"> 80</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp; 204/40&mdash;11.7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp; 203/42&mdash;10.4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 218/48&mdash;14.3</td>
+            </tr>
+            <tr>
+                <td align="center"> 88</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> ....</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 204/44&mdash;&nbsp;&nbsp;&nbsp; </td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> ....</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center">143</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 215/40.5&mdash;13.3</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> ....</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 225/48&mdash;15.1</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<h3>The Umbilical Scar</h3>
+<p>The umbilical cord is broken at birth and the navel closes within a few
+    days; but the scar, involving from two to four ventral scales, remains throughout
+    life. Position of the scar was found by Edgren (1951:1) to be sexually
+    dimorphic in the eastern hog-nose snake (<i>Heterodon platyrhinos</i>), but nothing
+    has been published on this matter concerning the cottonmouth. Consequently,
+    I counted the scales of several individuals from the anal plate, and there was
+    no marked difference in the position of the scar in males and females; it varied
+    in position from the 10th to the 18th scale. When counted from the anterior
+    end, the scar ranged from ventral number 115 to 122 (average, 119) in 28
+    females and from number 117 to 126 (average, 121) in 14 males. The difference
+    between male and female cottonmouths is not nearly so great as in <i>Heterodon</i>.</p>
+<h3>Later Growth and Bodily Proportions</h3>
+<p>The only records of growth increments in a natural population of cottonmouths
+    are those in Table 11. The period of growth is mostly the period of
+    activity, and differences are expected between northern and southern populations.
+    As size increases, determination of growth rate becomes more difficult
+    because age classes overlap in size. Growth of any individual depends not
+    only on climate and food but also on disease and parasitism and the innate <span class="pagenum"><a name="Page_458" id="Page_458">[458]</a></span> size potential. Stabler (1951:91) showed weight and length relationships in
+    two cottonmouths for a period of six and one-half years.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 11.&mdash;Growth Increments in Cottonmouths (Barbour, 1956:38-39).</p>
+<div class="c7">
+    <table cellpadding="2" summary="increments" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Number of<br />
+                    individuals</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Total length<br />
+                    in millimeters</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Estimated age<br />
+                    in months</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Estimated growth<br />
+                    from preceding year<br />
+                    in millimeters</td>
+            </tr>
+            <tr>
+                <td align="center"> 19</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 260-298</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7-8</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 25</td>
+            </tr>
+            <tr>
+                <td align="center"> 11</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 312-337</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 19-20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 45</td>
+            </tr>
+            <tr>
+                <td align="center"> 40</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 355-485</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 31-32</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 95&plusmn;</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" align="center"> 83</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 500-1000</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 43-44+</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> ?</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>My study failed to reveal any secondary sexual difference in growth rate
+    and maximum size. Of the 306 cottonmouths measured by me, 16 males and
+    five females exceeded 700 millimeters in snout-vent length. Two males were
+    more than 850 millimeters long. One cottonmouth lived in captivity for 18
+    years and 11 months (Perkins, 1955:262). The maximum total lengths were
+    reported by Conant (1958:186-187) to be 74 inches (1876 mm.) in <i>A. p.
+    piscivorus</i> and 54 inches (1370 mm.) in <i>A. p. leucostoma</i>.</p>
+<div class="figcenter" style="width: 500px;"> <img src="images/i_458.jpg" alt="Fig. 6. Head length ( ? ) and head width ( ? )" height="328" width="500" /> <span class="caption">Fig. 6. Head length (<span class="lfont"> &deg; </span>) and head width ( <span class="xlfont"> &middot; </span>) expressed as a percentage
+    of snout-vent length of living and preserved cottonmouths. Head length
+    was measured from the tip of the snout to the posterior end of the mandible.
+    Head width was measured across the supraocular scales, since accuracy was
+    greater than if measured at the posterior edge of the jaw. No sexual dimorphism
+    or geographical variation occurs in these characters.</span> </div>
+<p>Proportions of various parts of the body vary considerably depending on
+    age, size and, in some instances, sex. Heads are proportionately larger in
+    young than in adults (Fig. 6), as is true of vertebrates in general. This
+    larger head has survival value for the cottonmouth in permitting more venom <span class="pagenum"><a name="Page_459" id="Page_459">[459]</a></span> to be produced and in permitting it to be injected deeper than would be the
+
+    case if the proportions were the same as in adults. Relative to the remainder
+    of the snake the head is considerably larger than in the copperhead (Fitch,
+    1960:108) and slightly larger than in the rattlesnake, <i>Crotalus ruber</i> (Klauber,
+    1956:152).</p>
+<div class="figcenter" style="width: 500px;"><img src="images/i_459.jpg" alt="Fig. 7. Tail length expressed as a percentage of snout-vent length" height="275" width="500" /> <span class="caption">Fig. 7. Tail length expressed as a percentage of snout-vent length of living and preserved cottonmouths ( <span class="xlfont">&middot;</span>&mdash;males; <span class="lfont">&deg;</span>&mdash;females ). </span> </div>
+<p>In general, tails are relatively longer in males than in females of the same
+    size (Fig. 7), except that there is little or no difference at birth. Growth of
+    the tail in males proceeds at a more rapid rate. In certain individuals sex
+    cannot be recognized from length of the tail relative to snout-vent length because
+    overlapping occurs, especially in medium-sized individuals. Similar
+    changes of proportions with increase in age occur in copperheads (Fitch, 1960:106)
+    and rattlesnakes (Klauber, 1956:158-159), but the tail of the cottonmouth
+    is relatively much longer.</p>
+<hr class="chap" />
+<h2>SHEDDING</h2>
+<h3>The Shedding Operation</h3>
+<p>Shedding of the skin is necessary to provide for growth and wear in snakes.
+    The milkiness or bluing of the eyes, which causes partial blindness, marks the
+    initial stage of shedding and is caused by a discharge of the exuvial glands that
+    loosens the old <i>stratum corneum</i> from the layer below. In four to seven days
+    the opaqueness disappears, and the snake sheds after an additional three to six
+    days (Table 12). Young snakes first shed within a few days after birth and
+    generally shed more frequently than adults, but the interval is variable. The
+    eyes of three young cottonmouths observed by Wharton (1960:126) became
+    milky on the fourth day but cleared on the seventh day, and the skin was
+    shed on the eighth day. The eyes of three young kept by me became milky
+    two to three days after birth, cleared on the seventh to tenth days, and the
+    skin was shed on the thirteenth day. Possibly the relatively long interval in <span class="pagenum"><a name="Page_460" id="Page_460">[460]</a></span> this instance resulted from low relative humidity in the room where the
+    snakes were kept. According to Fitch (1960:134), litters of young copperheads
+    usually shed within three to ten days after birth; but under unusually
+    dry conditions shedding did not occur for several weeks.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 12.&mdash;Duration of Preparatory Period (in days) to Shedding in 11
+    Cottonmouths.</p>
+<div class="c7">
+    <table cellpadding="2" summary="duration" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px; border-bottom-style: solid; border-bottom-width: 1px;" align="center"> Duration of<br />
+                    cloudiness<br />
+                    of eyes</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Time between<br />
+                    clearing and<br />
+                    shedding</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double; border-bottom-style: solid;" align="center"> Time from beginning<br />
+                    of cloudiness<br />
+                    until shedding</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+            </tr>
+            <tr>
+                <td align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> -</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> -</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+            </tr>
+            <tr>
+                <td align="center"> -</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> -</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+            </tr>
+            <tr>
+                <td align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11</td>
+            </tr>
+            <tr>
+                <td align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 8</td>
+            </tr>
+            <tr>
+                <td align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> -</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> -</td>
+            </tr>
+            <tr>
+                <td align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-top: 1px solid rgb(0, 0, 0); border-bottom-style: solid;" align="center"><span style="text-decoration: overline">X</span> 5.4&nbsp;&nbsp;&nbsp; </td>
+                <td style="border-width: 1px; border-top: 1px solid rgb(0, 0, 0); border-left-style: solid; border-bottom-style: solid;" align="center"><span style="text-decoration: overline">X</span> 3.8&nbsp;&nbsp;&nbsp; </td>
+                <td style="border-width: 1px; border-top: 1px solid rgb(0, 0, 0); border-left-style: solid; border-bottom-style: solid;" align="center"><span style="text-decoration: overline">X</span> 9.0&nbsp;&nbsp;&nbsp; </td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>Cottonmouths as well as other snakes usually do not feed until after the
+    skin is shed and are generally quiescent during the period preceding shedding,
+    except that immediately before shedding they become active and rub their
+    snouts on some rough object and may yawn several times seemingly in an
+    attempt to loosen the skin along the edges of the lips. After the skin is
+    loosened from the head, more rubbing against rough surfaces and writhing
+    serves to pull the old skin off, turning it inside out. Once the old skin has
+    passed over the thick mid-body, the snake often crawls forward using rectilinear
+    locomotion until the skin is completely shed. It normally comes off in
+    one piece; but, if the snake is unhealthy or has not had sufficient food or
+    water, the skin may come off in patches. Frequently one or both of the
+    lens coverings are not shed immediately and impair the sight. Bathing or
+    swimming ordinarily causes dried skin to peel off; and, because of the cottonmouth's
+    aquatic habits, its chances of shedding successfully are much greater
+    than those of less aquatic snakes. Cottonmouths that have recently shed
+    have bright and glossy patterns, in contrast to the dull and dark appearance
+    of those that are preparing to shed.</p>
+<h3>Frequency of Shedding</h3>
+<p>Most of our knowledge concerning the frequency of shedding is based
+    upon observations of captives. It is known that the intervals between exuviations
+    are largely dependent upon the amount of food taken and the rate of
+    growth. Unless laboratory conditions closely resemble those in the field,
+    shedding frequencies in captives probably differ much from those of free-living
+    snakes.</p>
+<p>Only two of my captives shed twice. The intervals between exuviations <span class="pagenum"><a name="Page_461" id="Page_461">[461]</a></span> in the two snakes were eight and five months, lasting from August to April
+    and from December to May, respectively. Ten other snakes shed once in
+    the period from January through July. Stabler (1951:91) presented data
+    concerning shedding of two cottonmouths kept 12 and 14 years in captivity.
+    One shed 25 times in 12 years and the other shed 37 times in 14 years, giving
+    an average of 2.1 and 2.6 per year, respectively. Neither of the snakes
+    shed from December through March, but the period of shedding corresponded
+    to the period of greatest activity and growth. In Florida, cottonmouths shed
+    four to six times a year, according to rate of growth (Allen and Swindell,
+    1948:7).</p>
+<hr class="chap" />
+<h2>FOOD HABITS</h2>
+<h3>Methods of Obtaining Prey</h3>
+<p>Food is obtained by a variety of methods depending on the type of food,
+    age of the cottonmouth, and possibly other factors. Some captives lie in
+    ambush and others crawl slowly in active search. At the first cue of possible
+    prey, either by sight, scent, or differential temperature detection by the pit,
+    the snake appears to become alert and flicks its tongue out at fairly rapid
+    intervals.</p>
+<p>By means of the facial or loreal pit found in all crotalids, the snake is able
+    to detect objects having temperatures different from that of the surroundings
+    of the objects. In detecting prey the tongue acts to sharpen the sense of
+    &quot;smell&quot; by conveying particles to Jacobson's organs in the roof of the mouth.
+    On many occasions cottonmouths appeared to rely solely on sight; they
+    passed within a few inches of prey, apparently unaware of its presence until
+    it moved. When pools of water begin to dry up toward the end of summer,
+    cottonmouths often congregate and feed on dying fish. In these instances
+    the fish are usually taken as they come to the surface. In laboratory observations
+    moccasins seize live fish and some moccasins carry the fish until they
+    have received lethal doses of venom; afterward the fish are swallowed. But
+    grasping and manipulation of the prey occurs without the fangs' being employed,
+    especially in the case of dead fish. On one occasion a cottonmouth
+    was observed to grasp the edge of a glass dish that had contained fish and
+    apparently retained the odor. On another occasion I placed several fish in a
+    bowl, rubbed a stick on the fish, and then touched each snake lightly on the
+    nose with the stick. The snakes crawled directly to the bowl and began
+    feeding. At other times these same snakes crawled around the cage in an
+    apparent attempt to locate the food but paid little attention to fish held in
+    front of them. If the catching of prey under natural conditions were as
+    uncoordinated as it sometimes is in captivity, the snakes probably would not
+    be able to survive.</p>
+<p>Wharton (1960:127-129) described tail-luring in one individual of a 76-day-old
+    brood of cottonmouths. The snake lay loosely coiled with the tail
+    held about six centimeters from the ground; a constant waving motion passed
+    posteriorly through the terminal inch of the tail. These movements ceased
+    at 7:20 p.m. but were resumed at 7:40 a.m. the following day. All observations
+    were under artificial light. The &quot;caudal lure&quot; as a means of obtaining
+    prey has been described in other species and related genera by Neill (1960:194)
+    and Ditmars (1915:424).</p>
+<p>Various authors have suggested that the method of capture differs according
+    to the kind of prey. Allen and Swindell (1948:5) stated that cottonmouths
+    retain their hold after striking fish or frogs but will release a mouse after
+    delivering a bite and are timid in striking at larger rodents. Neill (1947:203)
+    noted that a cottonmouth always waited several minutes after biting a large
+    rat before approaching its prey. This same type of behavior has been reported
+    for copperheads (Fitch, 1960:194) and rattlesnakes (Klauber, 1956:618). <span class="pagenum"><a name="Page_462" id="Page_462">[462]</a></span> Cottonmouths observed by me retained a strong hold on fish, frogs, and
+    sometimes mice, but almost always released large mice and baby chicks,
+    which were not eaten until after death.</p>
+<p>Different behavior according to type of prey is correlated with ability of
+    prey to retaliate, although some animals may not be released because they
+    could easily escape. For instance, a frog could hop far enough to escape in
+    a matter of seconds if released. A 73-millimeter <i>Rana pipiens</i> that I observed
+    was bitten twice within one and a quarter hours and died 45 minutes after
+    the last bite. Its movement was uncoordinated by the time of the second bite,
+    but it could have escaped had the frog not been confined. Although it is
+    doubtful that normal, healthy fish are frequently captured by cottonmouths,
+    Allen (1932:17) reported that a cottonmouth was seen pushing a small,
+    dead pike about on the surface of a stream. A wound on the belly of the
+    fish indicated that it had been bitten. A 17-gram creek chub (<i>Semotilus</i>)
+    and a 13.7-gram bass (<i>Micropterus</i>) were injected by me with one-fourth
+    cubic centimeter of fresh venom near the base of the tail in order to determine
+    whether the fish could escape after being bitten and released. The creek
+    chub flipped onto its back after a minute and 45 seconds and gill movements
+    stopped in eight minutes and 35 seconds; the bass flipped over after 50 seconds
+    and died in two minutes and 10 seconds. The venom immediately affected
+    both fish, and it is unlikely that either could have swum more than a few feet.</p>
+<p>After its prey has been killed, a cottonmouth examines the body from end
+    to end by touching it with the tongue. Then the animal is grasped in the
+    mouth without the use of the fangs and is slowly manipulated until one end
+    (usually the head) is held in the mouth. The lengthy process of swallowing
+    then takes place, the fangs and lower jaws alternately pushing the prey down
+    the throat.</p>
+<h3>Food and Food Preferences</h3>
+<p>The cottonmouth seems to be an opportunistic omni-carnivore, because it
+    eats almost any type of flesh that is available, including carrion. It feeds
+    primarily upon vertebrates found in or near water; but invertebrates and
+    eggs have also been found in the diet. The only potential prey items that
+    seem not to be normally eaten are bufonid toads and tadpoles. I have
+    occasionally offered tadpoles and frogs to cottonmouths, but only the frogs
+    were accepted. But, Stanley Roth kept a cottonmouth in captivity that ate
+    both toads and tadpoles. If tadpoles are commonly eaten, their probable
+    rapid digestion would make identification almost impossible.</p>
+<p>Following is a list of known foods of the cottonmouth:</p>
+<blockquote>
+    <p>Captivity: &quot;... rattlesnake.... The same moccasin also killed
+        and ate a smaller snake of its own species....&quot; (Conant, 1934:382.)</p>
+    <p>Florida: &quot;3 heron feathers, bird bone, <i>Eumeces inexpectatus</i>, 3 fish all under
+        one inch in length, 1 heron egg shell&quot; (Carr, 1936:89). According to Allen
+        and Swindell (1948:5), &quot;the food included other moccasins, prairie rattlesnakes,
+        king-snakes, black snakes, water snakes, garter snakes, ribbon snakes,
+        and horn snakes ... most of the species of frogs, baby alligators, mice,
+        rats, guinea pigs, young rabbits, birds, bats, squirrels, and lizards ...
+        a mud turtle ... a case of a four footer eating ten to twelve chicken
+        eggs. The most common food appears to be fish and frogs. Catfish are
+        included on this list....&quot; Yerger (1953:115) mentions &quot;an adult yellow
+        bullhead, <i>Ameiurus natalis</i> ... 306 mm. in standard length [from a 63-inch
+        cottonmouth].&quot;</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_463" id="Page_463">[463]</a></span></p>
+<blockquote>
+    <p>Georgia: &quot;... full grown <i>Rana catesbeiana</i>, several foot-long pickerel
+        ... dead fish if placed in a pan of water.... <i>Natrix sipedon
+        fasciata</i> and <i>Masticophis flagellum</i> ... rats.... Toads and large <i>Eumeces laticeps</i> were always ignored.&quot; (Neill, 1947:203.) &quot;<i>Natrix</i>, <i>Heterodon</i>, <i>Kinosternon</i>, <i>Rana</i>, <i>Hyla cinerea</i>, <i>Microhyla</i>, Microtine [<i>Pitymys pinetorum</i>].&quot;
+        (Hamilton and Pollack, 1955:3.)</p>
+    <p>Mississippi: &quot;... <i>Hyla gratiosa</i>.... In captivity specimens have
+        eaten frogs, mice, birds, dead fish, pigmy rattlers and copperheads. Toads
+        ... were refused&quot; (Allen, 1932:17). One moccasin &quot;disgorged a smaller
+        decapitated moccasin ... killed the day before by boys&quot; (Smith and
+        List, 1955:123).</p>
+    <p>Tennessee: &quot;Beetles in one stomach; lizard (<i>Eumeces</i>) in another stomach;
+        small snake (<i>Natrix</i>) in one intestine, and hair in another intestine. One
+        stomach contained numerous bits of wood, up to four inches in length....&quot;
+        (Goodman, 1958:149.)</p>
+    <p>Kentucky: &quot;<i>Siren intermedia</i> was the most abundant food item in both
+        volume and occurrence. Frogs of the genus <i>Rana</i> ranked second. Together,
+        these two items comprised almost <span class="top">2</span>/<span
+ class="bottom">3</span> of the food of the snakes. The other
+        food items were distributed among the fishes, reptiles, and other amphibians
+        [one <i>Rana</i> tadpole included].&quot; (Based on 42 samples&mdash;Barbour, 1956:37.)</p>
+    <p>Illinois: (Based on 84 samples&mdash;Klimstra, 1959:5.)</p>
+    <div class="c7">
+        <table cellpadding="2" summary="food" cellspacing="0"
+  width="80%">
+            <tbody>
+                <tr>
+                    <td align="left"><i>Food Item</i></td>
+                    <td align="center"><i>Per cent Frequency<br />
+                        of Occurrence</i></td>
+                    <td align="center"><i>Per cent<br />
+                        Volume</i></td>
+                </tr>
+                <tr>
+                    <td align="left">Pisces</td>
+                    <td align="center">39.3</td>
+                    <td align="center">31.9</td>
+                </tr>
+                <tr>
+                    <td align="left">Amphibia</td>
+                    <td align="center">36.9</td>
+                    <td align="center">26.0</td>
+                </tr>
+                <tr>
+                    <td align="left">Reptilia</td>
+                    <td align="center">25.0</td>
+                    <td align="center">18.2</td>
+                </tr>
+                <tr>
+                    <td align="left">Mammalia</td>
+                    <td align="center">30.9</td>
+                    <td align="center">17.9</td>
+                </tr>
+                <tr>
+                    <td align="left">Gastropoda</td>
+                    <td align="center">17.8</td>
+                    <td align="center">1.0</td>
+                </tr>
+                <tr>
+                    <td align="left">Miscellaneous</td>
+                    <td align="center">25.0</td>
+                    <td align="center">5.0</td>
+                </tr>
+                <tr>
+                    <td align="center">(Algae, Arachnida, Aves, Insecta)</td>
+                    <td colspan="2" align="left">&nbsp;</td>
+                </tr>
+            </tbody>
+        </table>
+    </div>
+    <p>Louisiana: Penn (1943:59) mentions that a &quot;female had just eaten two
+        young cottonmouths....&quot; Clark (1949:259) mentions &quot;100 specimens&mdash;34
+        fish; 25 <i>Rana pipiens</i>; 16 <i>Rana clamitans</i>; 7 <i>Acris</i>; 4 <i>Natrix sipedon confluens</i>;
+        8 birds; 5 squirrels ... catfish thirteen and one-half inches in length
+        ... small-mouth black bass [eleven inches].&quot;</p>
+    <p>Oklahoma: Force (1930:37) remarks that the moccasin &quot;eats bullfrogs
+        ... but refuses leopard frogs.&quot; Trowbridge (1937:299) writes: &quot;several
+        sun perch.... Another had eaten six catfish six to ten inches long
+        ... a water snake (<i>Natrix s. transversa</i>) about 18 inches long ...
+        frogs, mostly <i>Rana sphenocephala</i>.&quot; Carpenter (1958:115) mentions &quot;a
+        juvenile woodthrush.... Seven last instar cicadas ... a young
+        cottontail.&quot; According to Laughlin (1959:84), one moccasin &quot;contained the
+        following items: 18 contour feathers of a duck, probably a teal; one juvenile
+        cooter turtle, <i>Pseudemys floridana</i>; and a large mass of odd-looking unidentifiable
+        material. The other cottonmouth contained one juvenile pond turtle, <i>Pseudemys scripta</i>....&quot;</p>
+    <p>Texas: &quot;... several ... feeding on frogs.... One ...
+        found DOR was found to contain a large catfish.&quot; (Guidry, 1953:54.)</p>
+</blockquote>
+<p>Of 246 cottonmouths that I examined for food items, only 46 contained
+    prey in their digestive tracts. Almost all of the snakes examined were
+    museum specimens that had been collected at many places over a period
+    of about 40 years. It was not known how long each had been kept alive
+    before being preserved. Therefore it was impossible to determine what
+    proportion of any population of cottonmouths could be expected to contain
+    food. The food items were not analyzed numerically because the scales and
+    hair, by means of which many food items in the intestine were identified,
+    yielded no clue as to the number of individuals actually present unless several <span class="pagenum"><a name="Page_464" id="Page_464">[464]</a></span> distinct kinds were found. Each occurrence of scales or hair was thus recorded
+    as a single individual, although some such occurrences may have represented
+    more than one animal. The contents of some stomachs were so well digested
+    that it was difficult to determine the number of items present. As a rule
+    only one food item was present in a digestive tract, but a few tracts contained
+    several items of the same or different species. Three frogs (<i>Acris crepitans</i>)
+    were in one snake and three hylas (<i>Hyla versicolor</i>) in another. Still another
+    individual captured beside a drying pond contained six individuals of <i>Lepomis</i> each about three inches long and two pikes (<i>Esox</i>) about six inches long.</p>
+<p style="text-align: center">&nbsp;</p>
+<p style="text-align: center">TABLE 13.&mdash;Analysis of Food Items of 46 Cottonmouths Collected in
+    Arkansas, Louisiana, and Texas (1922-1962).</p>
+<div class="c7">
+    <table cellpadding="2" summary="food items" cellspacing="0"
+ width="80%">
+        <tbody>
+            <tr>
+                <td style="border-top-style: double; border-top-width: 4px;" align="center">&nbsp;</td>
+                <td style="border-top-style: double; border-top-width: 4px;" align="center"><span class="smcap"> Food Items</span></td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double;" align="center"> Number of<br />
+                    samples in<br />
+                    which item<br />
+                    occurred</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double;" align="center"> Percent<br />
+                    frequency<br />
+                    of<br />
+                    occurrence</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double;" align="center"> Estimated<br />
+                    weight<br />
+                    in<br />
+                    grams</td>
+                <td style="border-left-style: solid; border-width: 4px 1px 1px; border-top-style: double;" align="center"> Estimated<br />
+                    percentage<br />
+                    by<br />
+                    bulk</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-top-style: solid;" colspan="2" align="left">Fish</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> (7)</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 13.2</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-top-style: solid;" align="center"> 18.4</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Esox</i> sp.</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Lepomis</i> sp.</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 15</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Unidentified</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left">Amphibians</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> (12)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 23.0</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20.4</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Scaphiopus hurteri</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 13</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Acris crepitans</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td>&nbsp;</td>
+                <td align="left"><i>Hyla cinerea</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Hyla versicolor</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Rana catesbeiana</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Rana pipiens</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 15</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Unidentified</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left">Reptiles</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> (15)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 28.4</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 29.9</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Pseudemys scripta</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 15</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Anolis carolinensis</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Eumeces fasciatus</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Lygosoma laterale</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Natrix</i> sp.</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Natrix erythrogaster</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 10</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Agkistrodon piscivorus</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Crotalus</i> sp.</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 30</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Unidentified snakes</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left">Birds</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> (4)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 7.6</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 18.6</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Anhinga anhinga</i> (juv.)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 60</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Egret (head and neck)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Passeriformes</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 2</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 20</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td colspan="2" align="left">Mammals</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> (6)</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 11.3</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12.7</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"><i>Blarina brevicauda</i></td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 1</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 12</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="center">&nbsp;</td>
+                <td align="left"> Cricetinae</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 5</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center"> 18</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td align="left">&nbsp;</td>
+                <td align="left">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px;" align="center">&nbsp;</td>
+            </tr>
+            <tr>
+                <td style="border-width: 1px; border-bottom-style: solid;" colspan="2" align="left">Unidentified</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> (9)</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center"> 17.0</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+                <td style="border-left-style: solid; border-width: 1px; border-bottom-style: solid;" align="center">&nbsp;</td>
+            </tr>
+        </tbody>
+    </table>
+</div>
+<p>The &quot;unidentified&quot; category (Table 13) refers to jellylike masses in the
+    stomach or material in the intestine in which no scales, feathers, hair, or bones <span class="pagenum"><a name="Page_465" id="Page_465">[465]</a></span> could be found. Most of the unidentifiable matter could be assumed to
+    consist of remains of amphibians, since they leave no hard parts. If this
+    assumption is correct, amphibians comprise about 40 per cent of the diet.
+    Since intestinal contents were included, a volumetric analysis was not feasible.
+    Therefore, the weight of each type of food item was estimated and the
+    percentage by bulk calculated from it (Table 13).</p>
+<p>Pieces of dead leaves and small sticks constituted most of the plant material
+    found and presumably were ingested secondarily because they adhered to the
+    moist skin of the prey, especially to fish and amphibians. However, some
+    plant materials probably are eaten because they have acquired the odor of
+    the prey. One cottonmouth contained a <i>Hyla cinerea</i>, several leaves, and five
+    sticks from 37 to 95 millimeters long and from 12 to 14 millimeters in diameter.</p>
+<p>Most reports in the literature state that gravid females do not feed, but
+    four gravid females examined by me containing large, well-developed embryos
+    also contained evidences of having recently fed. Two of them had scales of
+    snakes in the stomach or intestine, one contained a six-inch <i>Lepomis</i>, and the
+    other had hair in the intestine and the head and neck of an adult egret in the
+    stomach.</p>
+<hr class="chap" />
+<h2>MORTALITY FACTORS</h2>
+<h3>Natural Enemies and Predators</h3>
+<p>Published records of other animals preying on cottonmouths or killing them
+    are few. Reptiles more often than other classes of vertebrates prey on the
+    cottonmouth. McIlhenny (1935:44) reported on the scarcity of snakes in
+    areas where alligators were present. Predation on cottonmouths by indigo
+    snakes (<i>Drymarchon corais</i>) was reported by Conant (1958:153) and Lee
+    (1964:32). Allen and Swindell (1948:6) obtained a photograph of a king-snake
+    (<i>Lampropeltis getulus</i>) killing a cottonmouth but thought that moccasins
+    are not eaten by <i>L. getulus</i>. However, one occasion reported herein shows that
+    cottonmouths are eaten by king-snakes; and Clark (1949:252) reported finding
+    13 cottonmouths, along with other prey, in the stomach contents of 301 king-snakes
+    (<i>L. g. holbrooki</i>) from northwestern Louisiana. Cannibalism is also
+    common among cottonmouths. Klauber (1956:1058;1079) cited predation
+    on cottonmouths by a blue heron (<i>Ardea herodias</i>) and a largemouth bass
+    (<i>Micropterus salmoides</i>). Man is probably the greatest enemy of the cottonmouth.
+    Intentional killing, capturing, road kills, and alteration of the environment
+    destroy large numbers.</p>
+<h3>Parasites and Diseases</h3>
+<p>Allen and Swindell (1948:12) listed several diseases and parasites of snakes
+    and stated that &quot;some moccasins captured in the woods are so poor and weak
+    from parasitic infection that they can barely crawl.&quot; The only kind of ectoparasite
+    found on captive cottonmouths in the course of my study was a snake
+    mite, <i>Ophionyssus natricus</i>. An infestation of that mite was thought to be
+    partly responsible for the death of one captive moccasin. Other moccasins
+    spent increasing amounts of time in their water dish after they became
+    infected with mites. Under natural conditions frequent swimming probably
+    keeps cottonmouths nearly free of mites.</p>
+<p>Endoparasites found included lung flukes, stomach nematodes, and tapeworms.
+    Lung flukes (<i>Ochetosoma</i> sp.) were found in 16 of 20 captive cottonmouths. <span class="pagenum"><a name="Page_466" id="Page_466">[466]</a></span> Snails and frogs serve as intermediate hosts for various stages in
+    the life cycle of these flukes. The high percentage of cottonmouths infested
+    with flukes is indicative of the use of frogs as a major source of food. Less
+    than ten flukes were usually observed in the snakes' mouths but occasionally
+    more were seen. One snake was observed thrashing about in its cage for
+    nearly an hour, after which time it died. Upon examination of the mouth,
+    32 flukes were found, most of which were located in the Jacobson's organs.
+    Whether or not flukes caused the death is not known. Nematodes (<i>Kalicephalus</i> sp.) were found in the stomach of each of several preserved specimens;
+    most of these snakes had no food in their digestive tracts. In a high percentage
+    of the moccasins, tapeworms (<i>Ophiotaenia</i> sp.) were in the duodenum,
+    in many instances so tightly packed as seemingly to prevent passage of food.
+    The importance of fish in the diet is reflected by the high percentage of
+    snakes containing tapeworms. An unidentified cyst (?) about an inch long
+    and containing two hooks on one end was found attached to the outer wall
+    of the stomach of a cottonmouth. Yamaguti (1958) listed all the kinds
+    of helminths known from cottonmouths.</p>
+<h3>Miscellaneous Causes of Death</h3>
+<p>Munro (1949:71-72) reported on the lethal effect of 10 per cent DDT
+    powder on two young cottonmouths which were dusted with it to kill mites.
+    Herald (1949:117) reported an equal effect caused by spraying a five per cent
+    DDT solution in a room with several snakes. All but three large cottonmouths,
+    which were under shelter at the time of spraying, were killed.</p>
+<p>One individual that refused to eat was dissected soon after death, and a
+    short piece of a branch on which two large thorns were located at 90&deg; angles
+    was found blocking the intestine at the posterior end of the stomach.</p>
+<p>An unexpected and probably unusual circumstance caused the death of two
+    captives. After cleaning a cage containing five cottonmouths and placing
+    several mice in the cage for food, I noticed two of the snakes lying stretched
+    out, partially on one side, and almost unable to move. At first I thought they
+    had been bitten by other snakes which were in pursuit of the mice. The two
+    died after two days. When a similar incident occurred in another cage, I
+    removed the &quot;bitten&quot; snake and it fully recovered after 11 days. When
+    the same symptoms were observed in a garter snake in another cage, I
+    realized that in each instance the cage had been cleaned and fresh cedar
+    chips placed in it immediately prior to observation of these symptoms. Fine
+    cedar dust on the chips had evidently poisoned the snakes.</p>
+<hr class="chap" />
+<h2>BEHAVIOR</h2>
+<h3>Annual and Diel Cycles of Activity</h3>
+<p>In the days following emergence in spring, cottonmouths often endure uncomfortable
+    and even dangerous temperatures in order to obtain food and
+    mates. They are more sluggish at this time and more vulnerable to predation
+    than later in the season when temperatures are optimal. Fitch (1956:463)
+    found that copperheads in northeastern Kansas begin their annual cycle of
+    activity in the latter part of April, when the daily maximum temperature is
+    about 22&deg; C. and the minimum is about 4&deg; C., and become dormant in late <span class="pagenum"><a name="Page_467" id="Page_467">[467]</a></span> October or early November, at which time the daily maximum temperature is
+    about 15&deg; and the minimum is about 0&deg;. Indications are that in the northern
+    part of its range the annual activity cycle of the cottonmouth resembles that
+    of the copperhead in northeastern Kansas. Klimstra (1959:2) captured cottonmouths
+    from April to October in southern Illinois. Barbour (1956:36) collected
+    large numbers of them in early April in Kentucky and stated that they
+    migrate from swamps to wooded hillsides in late August and early September.
+    Spring migrations begin after a few consecutive warm days in March. In
+    northern Oklahoma cottonmouths have been found along the Verdigris River
+    as early as March, suggesting that a few winter in crayfish holes and mammal
+    burrows. The majority of individuals found in this area were at denning sites
+    along cliffs above the river and emerged later than those near the river (Dundee
+    and Burger, 1948:1-2). In Virginia cottonmouths have been seen as early as
+    March 5 (Martin and Wood, 1955:237) and as late as December 4. They
+    have been observed in migration from the swamps of the barrier beach to the
+    mainland in late October and early November in southeastern Virginia (Wood,
+    1954a:159). According to Neill (1947:204), the cottonmouth tolerates lower
+    temperatures than do most snakes in Georgia and is one of the last to go into
+    hibernation. Allen and Swindell (1948:4) stated that cottonmouths usually
+    bask during the mornings of the cooler months in Florida, but they mentioned
+    nothing of denning such as occurs farther north. Although winter aggregations
+    occur in the northern parts of the range, I have never seen such aggregations
+    in the South. However, in one instance related to me by a reliable
+    observer, seven cottonmouths were found together on a creek bank near the
+    Gulf Coast in early spring.</p>
+<p>During late summer and early autumn, fat is deposited in lobes in the lower
+    abdomen in preparation for the period of winter quiescence. Gravid females
+    usually do not feed so frequently or so much as other snakes, because they
+    tend to become inactive as the ova develop. Whether or not females feed
+    heavily after parturition and previous to denning is not known. Peaks of
+    activity in autumn may be caused by final attempts to feed before denning
+    and by the appearance of large numbers of newborn young. The young
+    usually have from one to two months in which to feed before the advent of
+    cold weather. According to Barbour's (<i>op. cit.</i>:38) findings, the young probably
+    feed before hibernation because they grow substantially in winter. For
+    those that do not feed, the rate of survival is perhaps much lower.</p>
+<p>In preparation for winter, cottonmouths migrate inland, usually to dry
+    forested hillsides where they den, commonly among rocks at the tops of bluffs,
+    along with several other species of snakes. In such aggregations there is no
+    hostility and each individual may derive benefit from contact with others by
+    which favorable conditions of temperature and humidity are maintained.</p>
+<p>Neill (1947:204) has found many specimens in winter by tearing bark from
+    rotting pine stumps on hillsides overlooking lakes or streams. On cold days
+    they evidently retreat below the surface, while on warm days they lie just
+    below the bark or emerge and bask. Neill believes that the use of stumps by
+    cottonmouths is an innate pattern of behavior, because of the large number
+    of young-of-the-year found in such surroundings. Cottonmouths were observed
+    in winter also under logs and stumps by Allen (1932:17). I have
+    twice observed cottonmouths crawling into crayfish burrows along the Gulf
+    Coast of Texas, and suppose they are used as denning sites to some extent.</p>
+<p><span class="pagenum"><a name="Page_468" id="Page_468">[468]</a></span></p>
+<p>The diel cycle of activity of cottonmouths is of necessity closely related
+    to the seasonal cycle. Since optimal temperatures determine activity, the
+    diel cycle varies greatly from time to time. It has been well established
+    that cottonmouths, like most other crotalids and many snakes of other families,
+    prefer nocturnal to diurnal activity, even though the temperature may be
+    less favorable at night. This preference is correlated with increased nocturnal
+    activity of frogs and reptiles that constitute the principal food supply.</p>
+<p>During spring and autumn, activity is more restricted to the day and long
+    periods of basking occur. However, as hot weather approaches, basking
+    occurs mainly in the morning and evening and activity becomes primarily
+    nocturnal. But, in well shaded, moist forests, cottonmouths feed actively in
+    the daytime.</p>
+<p>Availability of food also has an important influence upon activity. Allen and
+    Swindell (<i>op. cit.</i>:5) stated that moccasins congregate around drying ponds
+    and feed on dying fish until the moccasins can hold no more. They then
+    usually stay nearby as long as food remains. In an area of the Stephen F.
+    Austin Experimental Forest near Nacogdoches, Texas, many cottonmouths
+    journey daily to and from a swamp and a dry field, evidently to feed on
+    rodents inhabiting the area. Ten individuals captured along a snake-proof
+    fence that was built 30 yards from the swamp were found lying coiled along
+    the fence after 4:30 p.m., at which time the area was shaded. On another
+    occasion, I captured a large cottonmouth that was feeding upon dying fish
+    in a drying pool about 10:30 a.m. on August 19, 1962.</p>
+<p>Because of the aquatic habits of the cottonmouth, relative humidity probably
+    has little influence on the snake's activity. However, cottonmouths are
+    more restricted to the vicinity of water in dry weather than during rains or
+    muggy weather when many of their natural prey species also move about
+    more freely. Increased activity on cloudy days may result from protection
+    from long exposure to sunshine. Torrential rains and floods, such as those
+    following hurricanes along the Gulf and Atlantic coasts of the southeastern
+    United States, bring out quantities of snakes of all species. Rattlesnakes and
+    cottonmouths in particular are killed by the thousands at these times because
+    they seek shelter in human habitations. However, these are unusual circumstances
+    and do not reflect voluntary activity as a result of preferences.</p>
+<p>Thermal reactions of reptiles were classified by Cowles and Bogert (1944)
+    into several categories. For each species there is a basking and normal
+    activity range limited by the voluntary minimum and voluntary maximum at
+    which the animal seeks shelter. Beyond this normal range are the critical
+    thermal minimum and critical thermal maximum (C. T. M.) at which effective
+    locomotion is prevented. The lethal minimum and maximum are those
+    temperatures at which short exposure produces irreparable damage, and death
+    inevitably results. These classifications are modified somewhat by seasonal
+    or laboratory acclimation or by the physiological state of the animal. The
+    C. T. M. of five cottonmouths was determined by placing each individual
+    in an enclosed area and heating it with an infrared lamp. Cloacal temperatures
+    were taken with a Schultheis quick-recording thermometer as soon as
+    the snake could no longer right itself when placed on its back. All temperatures
+    were in degrees Celcius. The C. T. M. averaged 39.2&deg; (38.0&deg; to 40.0&deg;). A
+    temperature of 38.0&deg; was lethal to one individual. These cottonmouths had <span class="pagenum"><a name="Page_469" id="Page_469">[469]</a></span> been in captivity for nine months. The behavior of the snakes during heating
+    resembled those instances described by Klauber (1956:382-387) for rattlesnakes.
+    As the body temperature of the snakes rose past the optimum, each
+    individual became disturbed and tried to escape from the enclosure. The
+    snakes soon became frantic in their efforts to escape. After about five minutes
+    the mouth was opened and heavy, slow breathing was begun, accompanied by
+    a loss of coordination and a slowing down of movements. The snakes writhed
+    spasmodically for a few seconds and then lay still, usually with the mouth
+    open. Recovery was begun by rolling on the belly and flicking the tongue,
+    followed by movements of the head and then the body. Cottonmouths are
+    rarely exposed to dangerously high temperatures owing to their semi-aquatic
+    habits, but there are probably occasions when individuals reach the C. T. M.
+    for the species.</p>
+<h3>Basking</h3>
+<p>Since activity, digestion, and gestation depend upon adequate internal
+    temperatures, there must be a process by which these temperatures are attained
+    and for an appropriate time maintained. Basking is important in this respect.
+    The cottonmouths prefer to lie in a coiled position and, during basking, can
+    usually be found beside bodies of water or on branches of dead trees overhanging
+    the water. They are good climbers and have a prehensile tail that is
+    frequently employed in descending from small branches. Since cottonmouths
+    are semi-aquatic and are often exposed to temperatures that are lower than
+    those of the air, they either must bask more often than terrestrial snakes
+    or tolerate lower temperatures. Length of the period of basking is determined
+    not only by amounts of insolation and temperature but also by the size of the
+    snake. A smaller snake can reach its optimum temperature more rapidly
+    because of a higher surface-to-volume ratio. Another factor that may play
+    a minor role in the rate of temperature change is the color of the snake. The
+    wide variation in color of cottonmouths probably affects rates of heat increase
+    and loss due to direct radiation. Slight hormonal control of melanophores
+    described in snakes by Neill and Allen (1955) also may exert some influence
+    on the length of time spent basking. No rates of temperature increase or
+    decrease are available for cottonmouths.</p>
+<h3>Coiling</h3>
+<p>While inactive the cottonmouth spends most of its time lying in a coiled
+    position with the tail outermost, with the body usually wound into about one
+    and one-half cycles, and the head and neck in a reversed direction forming a
+    U- or S-shaped loop. From this position the snake is able to make a short
+    strike or a hasty getaway if necessary. In my opinion this position is used
+    primarily for basking or resting and only secondarily for feeding. Most
+    individuals appear to pursue their prey actively, not lying in ambush for the
+    approaching prey to the extent that most other crotalids do.</p>
+<p>Many of the cottonmouths that I kept in captivity were observed in a coiled
+    position for periods up to three or four days. Under natural conditions, however,
+    they are more active. Young cottonmouths are inclined to remain in a
+    coiled position for longer periods than older individuals.</p>
+<p><span class="pagenum"><a name="Page_470" id="Page_470">[470]</a></span></p>
+<h3>Locomotion</h3>
+<p>Four distinct types of locomotion have been described in snakes: horizontal
+    undulatory, rectilinear, sidewinding, and concertina (Klauber, 1956:
+    331-350). Most snakes are capable of employing two or more of these types
+    of progression, at least to a certain degree; but horizontal undulatory locomotion
+    is the most common method used by the majority of snakes, including
+    the cottonmouth. In this method the snake's body is thrown into lateral
+    undulations that conform with irregularities in the substrate. Pressure is
+    exerted on the outside and posterior surface of each curve, thus forcing the
+    body forward.</p>
+<p>Rectilinear locomotion is more useful to large, thick-bodied snakes which
+    use this method of progression, chiefly when they are prowling and unhurried.
+    This method depends upon the movement of alternate sections of the venter
+    forward and drawing the body over the ventral scales resting on the substratum
+    by means of muscular action. This mode of locomotion was most
+    frequently observed in captive cottonmouths when they were crawling along
+    the edge of their cages, especially when they were first introduced to the cages
+    and toward the end of the shedding process. The other two types of locomotion,
+    sidewinding and concertina, have not, to my knowledge, been observed
+    in the cottonmouth.</p>
+<p>Both the cottonmouth and the cantil have definite affinities for water and
+    are as likely to be found in water as out of it. Copperheads and rattlesnakes,
+    although not aquatic, are good swimmers. When swimming, a motion resembling
+    horizontal undulatory progression is used.</p>
+<h3>Disposition</h3>
+<p>The number of different opinions expressed in the literature concerning the
+    cottonmouth's disposition is not at all surprising. As with any species there is
+    a wide range of individual temperament, which is affected by many factors.
+    The cottonmouth is considered by some writers to be docile while others consider
+    it to be highly dangerous. Allen and Swindell (1948:7) described the
+    variability in temperament, even among individuals. They wrote: &quot;On rare
+    occasions, moccasins are found which will attack. A perfectly docile snake
+    will turn and bite viciously without any apparent reason.&quot; They also recounted
+    a case in which a cottonmouth was kept as a pet for six years, being
+    allowed the freedom of the house. Smith and List (1955:123) found them
+    &quot;... surprisingly docile in the gulf region [Mississippi], displaying none
+    of the pugnacity of more northern cottonmouths.&quot; Smith (1956:310) stated:
+    &quot;Unlike the copperhead, cottonmouths are pugnacious; their powerful jaws,
+    long fangs, vicious disposition and potent venom make them a very dangerous
+    animal.&quot;</p>
+<p>My own observations are in general agreement with the statements of Allen
+    and Swindell (<i>loc. cit.</i>). In my encounters with cottonmouths, I have never
+    found any aggressive individuals except for three juveniles that were born in
+    captivity. In their first three days in the laboratory these juveniles were observed
+    to strike repeatedly whenever anyone entered the room. After this short
+    period of aggressiveness, however, they slowly became more docile. The disposition
+    shown by the newborn young is clearly an innate behavioral pattern
+    that undoubtedly has a direct relationship to survival. The majority of cottonmouths <span class="pagenum"><a name="Page_471" id="Page_471">[471]</a></span> that I have approached in the field have moved swiftly to seek refuge
+    in nearby water; a few have remained motionless as I approached, and one
+    showed the typical threat display. Upon capture and handling, they react
+    similarly to other pit-vipers by opening and closing the mouth and erecting
+    the fangs in an attempt to bite. They often bite through the lower jaw and
+    eject venom at this time as well as when the mouth is open. Of more than a
+    dozen individuals kept in captivity, four were particularly difficult to handle
+    whereas another was extremely docile. It was almost never found in aggregations
+    with the other snakes and did not struggle or attempt to bite when
+    handled. The majority remained unpredictable in disposition, usually appearing
+    docile and lazy but capable of extremely rapid movements when disturbed.</p>
+<h3>Defense and Escape</h3>
+<p>The typical threatening posture of rattlesnakes is all but lacking in the
+    cottonmouth, which relies primarily on concealing coloration or nearness to
+    water for escape. When approached, it usually plunges into nearby water or
+    remains motionless with the head held up at a 45&deg; angle and the mouth
+    opened widely exposing the white interior. The tail is sometimes vibrated
+    rapidly and musk is expelled. This threat display is unique to cottonmouths;
+    although it does not attract as much attention as the display of rattlesnakes,
+    it is probably an effective warning to most intruders at close range.</p>
+<p>Neill (1947:205) reported one case in which a cottonmouth used the &quot;body
+    blow&quot; defense, described for <i>Crotalus</i> by Cowles (1938:13), when approached
+    by a king-snake, <i>Lampropeltis getulus</i>. In this unusual posture the anterior
+    and posterior portions of the body are held against the ground and the middle
+    one-fourth to one-third of the body is lifted up and used in striking the
+    intruder. This same defense posture also was observed in rattlesnakes when
+    presented with the odor of the spotted skunk, <i>Spilogale phenax</i>. However, the
+    &quot;king-snake defense posture&quot; is probably not a well-established behavioral
+    pattern in the cottonmouth, for it sometimes feeds upon king-snakes. I observed
+    the killing and devouring of a cottonmouth by a speckled king-snake, <i>L. g. holbrooki</i>; the only attempts to escape were by rapid crawling and biting.</p>
+<p>Cottonmouths often squirt musk as a defensive action. The tail is switched
+    back and forth, and musk is emitted from glands on each side of the base of
+    the tail. The fine jets of musk are sprayed upward at about 45&deg; angles for a
+    distance of nearly five feet. How often this defense mechanism is used against
+    other animals is not known, but the musky odor can frequently be detected in
+    areas where cottonmouths are common. The odor is repulsive and, if concentrated,
+    can cause nausea in some individuals. To me, the scent is indistinguishable
+    from that of the copperhead.</p>
+<h3>&quot;Head Bobbing&quot;</h3>
+<p>&quot;Head bobbing&quot; in snakes has been described frequently in the literature,
+    and many interpretations have been advanced to explain its occurrence. One
+    of the earlier accounts was that of Corrington (1929:72) describing behavior
+    of the corn snake, <i>Elaphe guttata</i>. Characteristic bobbing occurred when the
+    snake was cornered, and seemingly the purpose was to warn or frighten foes.
+    Neill (1949:114-115) mentioned the jerking or bobbing of the head in several
+    species of snakes including the cottonmouth, and remarked that &quot;it is apparently <span class="pagenum"><a name="Page_472" id="Page_472">[472]</a></span> connected with courtship and with the recognition of individuals.&quot;
+    According to Munro (1950:88), &quot;head bobbing&quot; appears to be a sign of
+    annoyance in some instances but is usually concerned with reproduction and
+    individual recognition. Richmond (1952:38) thought that many types of
+    head movements among not only reptiles but also birds and some mammals
+    are a result of poor vision and serve &quot;to delimit and orient an object that for
+    lack of motion is otherwise invisible.&quot; Head movements undoubtedly occur
+    in animals to facilitate accommodation, but it is obvious from Richmond's
+    conclusions that he has never observed &quot;head bobbing&quot; in snakes. The term
+    itself is grossly misleading and should be discarded. Mansueti (1946:98)
+    correctly described the movements as spastic contractions of the body. I have
+    observed numerous instances of these movements in cottonmouths, copperheads,
+    and rat snakes (<i>Elaphe obsoleta</i>); and in no case has the movement
+    resembled a head bob as is described in lizards and other animals. The movement
+    appears to be a result of a nervous or sexually excited state and consists
+    of highly spastic contractions confined to the anterior part of the snake most
+    of the time but affecting the entire body on some occasions.</p>
+<p>I found the response to be most common among cottonmouths in confinement
+    when food was introduced to a cage containing several individuals
+    (increasing the tendency to strike at a moving object) and when an individual
+    was placed back in the cage after being handled. At these times the snakes
+    that were inactive began to jerk for a few seconds. When the snake is in
+    this seemingly nervous state, the same response is elicited by another snake
+    crawling over it. At other times the movement of one individual causes no
+    such response. The jerking movements appear to be released by the recognition
+    of a nervous state in another individual and may serve to protect the
+    jerking individual from aggressive advances of the former.</p>
+<p>Where courtship is involved, the jerking motions are made in conjunction
+    with writhing of the male and do not result from the same type of releaser
+    described above.</p>
+<h3>Combat Dance</h3>
+<p>The so-called combat dance between male snakes has long been known,
+    but its significance is still poorly understood. It was for many years believed
+    to be courtship behavior until the participants were examined and found to
+    be males. Carr and Carr (1942:1-6) described one such instance in two
+    cottonmouths as courtship. In their observations, as well as those of others,
+    copulation was never observed following the &quot;dance&quot; but was assumed to be
+    the ultimate goal. After the discovery that only males participated, it was
+    suggested that combat involved competition for mates, but the &quot;dance&quot; has
+    been observed at times other than the breeding season (Ramsey, 1948:228).</p>
+<p>Shaw (1948:137-145) discussed the combat of crotalids in some detail but
+    drew no conclusions as to the cause of the behavior. Lowe (1948:134) concluded
+    with little actual evidence that combat among male snakes is solely
+    for territorial purposes. Shaw (1951:167) stated that combat may occur as
+    a possible defense against homosexuality. One case of homosexual mating
+    among cottonmouths was reported (Lederer, 1931:651-653), but the incomplete
+    description seems to be of normal courtship procedure except that the
+    &quot;female&quot; tried to avoid the male. Two instances of combat observed between
+    timber rattlesnakes (<i>C. h. horridus</i>) by Sutherland (1958:23-24) were definitely <span class="pagenum"><a name="Page_473" id="Page_473">[473]</a></span> initiated because of competition for food. More observations are needed before
+    the significance of the combat can be fully understood.</p>
+<hr class="chap" />
+<h2>THE VENOM</h2>
+<h3>Properties of the Venom</h3>
+<p>The venom and poison apparatus have developed primarily as a means of
+    causing rapid death in small animals that are the usual prey. As a protective
+    device against larger enemies, including man, the venom may have some
+    value; but this was probably unimportant in the evolution of the poison
+    mechanism. A secondary function of the venom is to begin digestion of tissues
+    of the prey. Since food is swallowed whole, injection of digestive enzymes
+    into the body cavity enhances digestion of the prey.</p>
+<p>Kellogg (1925:5) described venom as a somewhat viscid fluid of a yellowish
+    color and composed of 50 to 70 per cent proteins, the chief remaining components
+    being water and carbohydrates, with occasional admixtures of abraded
+    epithelial cells or saprophytic microorganisms. Salts, such as chlorides, phosphates
+    of calcium, magnesium, and ammonium, occur in small quantities. Each
+    of the components of snake venom has a different effect on the body of the
+    victim. It was at first believed that there were two types of venoms:
+    neurotoxic, which acts upon nervous tissue; and haemotoxic, which acts on
+    blood and other tissues. It has since been found that venoms are composed
+    of varying mixtures of both types. Fairley (1929:301) described the constituents
+    of venom as: (1) neurotoxic elements that act on the bulbar and
+    spinal ganglion cells of the central nervous system; (2) hemorrhagins that
+    destroy the lining of the walls of blood vessels; (3) thrombose, producing
+    clots within blood vessels; (4) hemolysins, destroying red blood corpuscles;
+    (5) cytolysins that act on leucocytes and on cells of other tissues; (6) elements
+    that retard coagulation of the blood; (7) antibactericidal substances;
+    and (8) ferments that prepare food for pancreatic digestion. Elapid snakes
+    tend to have more of elements 1, 4, and 6 in their venoms, while viperids and
+    crotalids, of which the cottonmouth is one, have higher quantities of elements
+    2, 3, and 5. Kellogg (<i>loc. cit.</i>) stated that venom of cottonmouths contains
+    more neurotoxin than that of rattlesnakes and not only breaks down the nuclei
+    of ganglion cells but also produces granular disintegration of the myelin sheath
+    and fragmentation of the conducting portions of nerve fibers.</p>
+<p>Thus, venoms contain both toxic elements and non-toxic substances that
+    promote rapid spreading of the venom through the body of the victim. Jacques
+    (1956:291) attributed this rapid spreading to the hyaluronidase content of
+    venoms.</p>
+<h3>Venom Yield and Toxicity</h3>
+<p>One of the most important yet undeterminable factors of the gravity of
+    snakebite is the amount of venom injected into the victim. Since this volume
+    varies considerably in every bite, attempts have been made to determine the
+    amount and toxicity of venom produced by each species of poisonous snake.
+    Individual yield is so variable that a large number of snakes must be milked in
+    order to determine the average yield. Even then there remains an uncertainty
+    as to how this amount may compare with that injected by a biting snake.</p>
+<p>Wolff and Githens (1939b:234) made 16 venom extractions from a group <span class="pagenum"><a name="Page_474" id="Page_474">[474]</a></span> of cottonmouths in a two-year period. The average yield per snake fluctuated
+    between 80 and 237 milligrams (actual weight), and toxicity measured as the
+    minimum lethal dose for pigeons varied from 0.05 to 0.16 milligrams (dry
+    weight). No decrease in yield or toxicity was evident during this period.
+    Another group of cottonmouths from which venom was extracted over a
+    period of five years also showed no decrease in yield or toxicity. Of 315 individual
+    extractions the average amount obtained from each individual was
+    0.55 cubic centimeters of liquid or 0.158 grams of dried venom (28.0 per cent
+    solids). The minimum lethal dosage (M. L. D.) which was determined by
+    injecting intravenously into 350-gram pigeons was found to be 0.09 milligrams
+    (dry weight). Each snake carried approximately 1755 M. L. D.'s of venom.</p>
+<p>The record venom extraction for the cottonmouth was 4.0 cubic centimeters
+    (1.094 grams dried venom) taken from a five-foot snake which had been in
+    captivity for 11 weeks and milked five weeks earlier (Wolff and Githens,
+    1939a:52). The average yield of venom of cottonmouths is about three times
+    the average yield reported for copperheads by Fitch (1960:256), a difference
+    correlated with the greater bulk and relatively large head of the cottonmouth.</p>
+<p>Allen and Swindell (1948:13) stated that cottonmouth venom rates third
+    in potency, compared drop for drop to that of <i>Micrurus fulvius</i> and <i>Crotalus
+    adamanteus</i>. Freshly dried cottonmouth venom tested on young white rats
+    showed the lethal dose to be from 23 to 29 milligrams per kilogram of body
+    weight. The venom of 11 one-week-old cottonmouths was found to be more
+    potent than that of adult males. Githens (1935:171) rated <i>C. adamanteus</i> venom as being weaker than that of the copperhead (<i>A. contortrix</i>), which he
+    rated only slightly lower than cottonmouth venom. The crotalids which he
+    ranked more toxic than cottonmouths are: the Pacific rattlesnake (<i>C. viridis
+    oreganus</i>) and the massasauga (<i>S. catenatus</i>). He found <i>A. bilineatus</i>, <i>C.
+    durissus</i>, and <i>C. v. lutosus</i> to have the same toxicity as cottonmouths. Minton
+    (1953:214) found that the intraperitoneal &quot;lethal dose 50&quot; (the dose capable
+    of killing half the experimental mice receiving injections of it) was 6.36 milligrams
+    per kilogram for copperheads. However, in later publications Minton
+    (1954:1079; 1956:146) reported that the &quot;lethal dose 50&quot; for copperheads was
+    25.65 milligrams. Approximately the same potency was determined for cottonmouths.
+    Several rattlesnakes that he tested showed a higher toxicity than
+    copperheads or cottonmouths.</p>
+<p>Criley (1956:378) found the venom of copperheads to be 6.95, nearer
+    Minton's earlier estimate, and rated cottonmouth venom as being twice as
+    toxic as that of copperheads. The relative toxicities of other crotalids tested,
+    considering the cottonmouth to be one unit, were: <i>C. basiliscus</i>, 0.3; <i>A. contortrix</i>,
+    0.5; <i>C. viridis oreganus</i>, 1.4; <i>A. bilineatus</i>, 2.2; <i>C. adamanteus</i>, 2.3; <i>C. v.
+    viridis</i>, 3.2; <i>C. durissus terrificus</i>, 27.5.</p>
+<p>It can be seen from the above examples that toxicity of venoms and the
+    resistance of the animal receiving an injection of venom is highly variable.
+    Possibly the venom of each species of snake has greatest effect on animals of
+    the particular group relied on for food by the snake. If that is so, the venom
+    of cottonmouths would be expected to be more toxic when tested on fish,
+    reptiles, and amphibians than on birds and mammals. Likewise, the venom
+    of most species of rattlesnakes would be expected to be more virulent when
+    injected into mammals than when injected into lower vertebrates. But, according
+    to Netting (1929:108), species of rattlesnakes that prey on cold-blooded <span class="pagenum"><a name="Page_475" id="Page_475">[475]</a></span> animals, which are less susceptible to venoms than warm-blooded
+    animals, are thought to have highly toxic venoms. This explanation accounts
+    for the powerful venom of <i>Sistrurus catenatus</i>; and, in this respect, venom of
+    cottonmouths should be highly toxic also. However, no clear-cut trends have
+    been shown in most cases. Allen (1937) injected 250-gram guinea pigs with
+    4 milligrams of venom of various poisonous snakes. Survival time was recorded
+    in order to indicate the relative potency of the venoms. Of 16 such tests <i>C.
+    adamanteus</i> held places 1, 2, 3, 12, and 16; <i>Bothrops atrox</i> held places 4, 9,
+    10, and 13; and <i>A. piscivorus</i> held places 5, 7, 8, and 15. Places 6, 11, and 14
+    were held by three individuals of different species. No relationship to size
+    or sex was indicated by the results of this experiment.</p>
+<h3>Susceptibility of Snakes</h3>
+<p>Numerous experiments have been conducted to determine the susceptibility
+    of various snakes to venom. The majority of these experiments were performed
+    to learn whether or not venomous snakes were immune to their own
+    poison. Conant (1934:382) reported on a 30-inch cottonmouth that killed
+    two Pacific rattlesnakes and another cottonmouth. One rattlesnake was bitten
+    on the tail and the other on or near the head and partially swallowed. Gloyd
+    (1933:13-14) recorded fatal effects to a rattlesnake from the bite of a cottonmouth.
+    He also reported on the observations of three other crotalids bitten
+    by themselves or other snakes, from which no harmful effects were observed.
+    Allen (1937) injected several snakes with dried cottonmouth venom which
+    was diluted with distilled water just before each injection. Four cottonmouths
+    receiving 9, 18, 19, and 20 milligrams of venom per ounce of body weight survived,
+    while another receiving 18.7 milligrams per ounce died after three hours.
+    A specimen of <i>S. miliarius</i> receiving 8.3 milligrams per ounce died in about
+    ten hours, while a <i>C. durissus</i> receiving 12.5 milligrams per ounce succumbed
+    in 45 minutes. An alligator receiving 6 milligrams per ounce died in 14 hours.
+    Even the snakes that survived showed some degree of swelling.</p>
+<p>The studies of Keegan and Andrews (1942:252) show that king-snakes are
+    sometimes killed by poisonous snakes. A <i>Lampropeltis calligaster</i> injected with <i>A. contortrix</i> venom (0.767 milligrams per gram) died five days following the
+    injection. This amount was more than twice the amount of <i>A. piscivorus</i> venom injected into a <i>L. getulus</i> by Allen (1937) in which the snake showed
+    no ill effects. Keegan and Andrews (<i>loc. cit.</i>) stated that success in overpowering
+    and eating poisonous snakes by <i>Lampropeltis</i> and <i>Drymarchon</i> may be due
+    to the ability to avoid bites rather than to immunity to the venom. However,
+    Rosenfeld and Glass (1940) demonstrated that the plasma of <i>L. g. getulus</i> had an inhibiting effect on the hemorrhagic action on mice of the venoms of
+    several vipers.</p>
+<p>One of the more extensive studies on effects of venoms on snakes is that
+    by Swanson (1946:242-249). In his studies freshly extracted liquid venom
+    was used. His studies indicated that snakes are not immune to venom of
+    their own kind or to closely related species. Copperhead venom killed copperheads
+    faster than did other venoms but took more time to kill massasaugas,
+    cottonmouths, and timber rattlers. However, most of the snakes were able to
+    survive normal or average doses of venom although they are not necessarily
+    immune to it.</p>
+<p><span class="pagenum"><a name="Page_476" id="Page_476">[476]</a></span></p>
+<p>One of the major problems in comparing the data on toxicity of venom
+    in studies of this type is that no standard method of estimating toxicity has
+    been used. Swanson's (<i>loc. cit.</i>) amount of venom equalling one minim
+    (M.L.D.?) ranged from 0.058 to 0.065 cubic centimeters. There were no
+    different values given for each species, but the time that elapsed from injection
+    of the venom to death represented the toxicity. There also was no attempt
+    in his study to convert the amount of venom used into a ratio of the volume
+    of venom per weight of snake, making the results somewhat difficult to interpret.
+    Additional work in this field should provide for many injections into
+    many individuals of several size classes. The studies to date have been on
+    far too few individuals to allow statistical analyses to be accurate.</p>
+<hr class="chap" />
+<h2>THE BITE</h2>
+<h3>Effects of the Bite</h3>
+<p>Factors determining the outcome of snakebite are: size, health, and species
+    of snake; individual variation of venom toxicity of the species; age and size
+    of the victim; allergic or immune responses; location of the bite; and the
+    amount of venom injected and the depth to which it is injected. The last
+    factor is one of the most variable, owing to (1) character and thickness of
+    clothing between the snake and the victim's skin, (2) accuracy of the snake's
+    strike, and (3) size of the snake, since a large snake can deliver more venom
+    and at a greater depth than can a small snake.</p>
+<p>Pope and Perkins (1944) demonstrated that pit-vipers of the United States
+    bite as effectively as most innocuous snakes and that a careful study of the
+    bite may reveal the location of the pocket of venom, size of the snake, and
+    possibly its generic identity (see Dentition). The bite pattern of the cottonmouth
+    as well as the other crotalids showed the typical fang punctures plus
+    punctures of teeth on both the pterygoid and mandible. Even so, a varying
+    picture may be presented because from one to four fang marks may be present.
+    At times in the fang-shedding cycle three and even four fangs can be in
+    operation simultaneously.</p>
+<p>Various authors have attributed death of the prey to the following causes:
+    paralysis of the central nervous system, paralysis of the respiratory center,
+    asphyxiation from clotting of the blood, stoppage of the heart, urine suppression
+    due to crystallized hemoglobin in the kidney tubules, dehydration of
+    the body following edema in the area of the bite, or tissue damage. Mouths
+    of snakes are reservoirs for infectious bacteria, which are especially prolific in
+    damaged tissue. Bacterial growth is aided by the venom which blocks the
+    bactericidal power of the blood.</p>
+<p>Three grades in the severity of snakebite (I, minimal; II, moderate; and
+    III, severe) were described by Wood, Hoback, and Green (1955). Parrish
+    (1959:396) added a zero classification to describe the bite of a poisonous
+    snake in which no envenomation occurred. Grade IV (very severe) was
+    added by McCollough and Gennaro (1963:961) to account for many bites
+    of the eastern and western diamondback rattlesnakes.</p>
+<p>The first symptom of poisonous snakebite is an immediate burning sensation
+    at the site of the bite. Within a few minutes the loss of blood into the tissues
+    causes discoloration. Swelling proceeds rapidly and can become so great as
+    to rupture the skin. Pain is soon felt in the lymph ducts and glands. Weakness, <span class="pagenum"><a name="Page_477" id="Page_477">[477]</a></span> nausea, and vomiting may ensue at a relatively early stage. Loss of
+    blood into tissues may spread to the internal organs. In conjunction with a
+    rapid pulse, the blood pressure and body temperature can drop. Some difficulty
+    in breathing can occur, especially if large amounts of neurotoxin are
+    present in the venom. In severe cases the tension due to edema obstructs
+    venous and even arterial flow, in which case bacteria may multiply rapidly in
+    the necrotic tissue and gangrene can occur. Blindness due to retinal hemorrhages
+    may occur. Symptoms of shock may be present after any bite.</p>
+<h3>Treatment</h3>
+<p>Perhaps one of the most important factors in the outcome of snakebite is
+    the treatment. Because of the variable reactions to snakebite, treatment
+    should vary accordingly. Many methods have been proposed for treating
+    snakebite, and there is disagreement as to which is the best. The list of
+    remedies that have been used in cases of snakebite includes many that add
+    additional injury or that possibly increase the action of the venom. The use
+    of poultices made by splitting open living chickens and the use of alcohol,
+    potassium permanganate, strychnine, caffeine, or injection of ammonia have
+    no known therapeutic value, and may cause serious complications. The most
+    important steps in the treatment of snakebite are to prevent the spread of
+    lethal doses of venom, to remove as much venom as possible, and to neutralize
+    the venom as quickly as possible.</p>
+<p>It is generally agreed that the first step in snakebite treatment should be
+    to place a ligature above the bite to restrict the flow of venom, and also to
+    immobilize the patient as much as possible. The ligature should be loosened
+    at least every fifteen minutes. The next steps are sterilization of the skin and
+    the making of an incision through the fang punctures. As pointed out by
+    Stahnke (1954:8), the incision should be made in line with the snake's body
+    at the time of the bite, so as to account for the rearward curvature of the fangs
+    and possibly to reach the deposition of venom. Many instruction booklets
+    and first-aid guides have specified the length and depth of incision to be
+    made, but the actual size and depth of the cut should depend upon the location
+    of the bite. An &quot;X&quot; cut or connection of the fang punctures is likely to
+    facilitate the spread of the venom. No cut should be made that would sever
+    a large blood vessel or ligament.</p>
+<p>Extensive damage is often caused by well-meaning individuals whose attempts
+    at first aid result in brutally deep incisions and tourniquets applied too
+    tightly and for too long a period of time; the resultant damage in many instances
+    exceeds that of the bite itself (Stimson and Engelhardt, 1960:165).
+    Stimson and Engelhardt also think that time should be sacrificed to surgical
+    cleanliness, and incisions should not be made if a hospital can be reached
+    within an hour.</p>
+<p>The ligature-cryotherapy (L-C) method proposed by Stahnke (1953) has
+    been severely criticized by other workers. He stated that the ligature should
+    be tight enough to restrict completely the flow of venom until the temperature
+    of the area can be lowered sufficiently to prevent any action of the venom.
+    After 10 minutes the ligature may be removed and the bitten area kept immersed
+    in a vessel of crushed ice and water. If the envenomized member is
+    to be treated for more than four hours (which is the case with almost all <span class="pagenum"><a name="Page_478" id="Page_478">[478]</a></span> pit-viper bites), it should be protected by placing it in a plastic bag. The
+    venom action should be tested after 12 or more hours. This consists of a brief
+    warming period to determine whether or not the action of the venom can be
+    felt. The patient should be kept warm at all times; and the warming at the
+    termination of treatment should be done gradually, preferably by allowing
+    the water to warm slowly to room temperature.</p>
+<p>Advocates of the L-C method warn against making incisions unless they
+    are absolutely necessary, the theory being that each cut permits additional
+    bacterial infection and does little good in removing venom. However, McCollough
+    and Gennaro (1963:963) demonstrated that, in bites where the
+    fangs had only slightly penetrated the skin, more than 50 per cent of the
+    venom was removed in some instances if suction was started within three
+    minutes after the injection. With deeper injection the amount of venom
+    recovered sometimes reached 20 per cent of the dose. Stahnke suggested that
+    an incision be made at the site of the bite only after the site has been
+    refrigerated for at least 30 minutes.</p>
+<p>Stimson and Engelhardt (<i>loc. cit.</i>) stated that two constricting bands
+    should be used between the bite and the body and that cracked ice in a cloth
+    should be applied to the bite before reaching a hospital. In addition, they
+    suggested the following procedure. Rings of incisions should follow the swelling,
+    and suction should continue for several hours. After the edema has
+    receded, the limb should be wrapped in a towel containing crushed ice.
+    Antivenin should be given only in severe cases. Calcium gluconate and gas
+    gangrene antitoxin as well as antibiotics are helpful.</p>
+<p>The most recent and up-to-date summary of snakebite treatment is that by
+    McCollough and Gennaro (1963). Following is a brief summary of their
+    suggestions:</p>
+<p>1. Immobilization&mdash;Systemic immobilization is effected by body rest and
+    locally by splinting the bitten area.</p>
+<p>2. Tourniquet&mdash;A lightly occlusive tourniquet during a 30- to 60-minute
+    period of incision and suction would seem to possess some advantages. In
+    severe cases where medical attention is hours away, a completely occlusive
+    tourniquet may be necessary to prevent death. Sacrifice of the extremity may
+    be necessary for the preservation of life.</p>
+<p>3. Incision and suction&mdash;Suction should begin three to five minutes after
+    injection of venom if symptoms of poisoning are present. Incisions one-fourth
+    inch to an inch long across each fang mark should be made in order to open
+    the wound for more efficient suction. Multiple incisions are not useful for the
+    removal of venom but may be employed under hospital conditions to reduce
+    subcutaneous tensions and ischemia.</p>
+<p>4. Cryotherapy&mdash;An ice cap over the site of the bite for relief of pain
+    would seem to be permissible, especially prior to the administration of antivenin.
+    It must be remembered that cooling during the administration of the antivenin
+    radically reduces the access of the antiserum to the bite area.</p>
+<p>5. Antivenin&mdash;Antiserum is the keystone to the therapy of snakebite. Careful
+    evaluation of the severity of the bite and the patient's sensitivity should be
+    made before the use of antivenin. In Grade II (moderate) bites, the intramuscular
+    injection on the side of the bite may suffice. In Grades III (severe)
+    and IV (very severe), shock and systemic effects require intravenous injection.
+    In bites producing symptoms of this severity, antivenin must be given in <span class="pagenum"><a name="Page_479" id="Page_479">[479]</a></span> amounts large enough to produce clinical improvement. Ten to 20 units may
+    be necessary to prevent the relapse that sometimes occurs after small doses
+    of antivenin. Permanent remission of swelling and interruption of necrosis are
+    the therapeutic end point in the clinical use of the antiserum.</p>
+<p>In all cases of snakebite where there is any doubt as to the snake's identity,
+    it should be killed if possible and taken to the hospital for positive identification.
+    In many instances of actual bites by poisonous snakes the only treatment
+    needed was an injection of tetanus antitoxin or toxoid and sedation, because
+    physical examination revealed no indication of poisoning (Stimson and Engelhardt, <i>loc. cit.</i>).</p>
+<h3>Case History of a Bite</h3>
+<p>On July 29, 1963, at 8:20 a.m., I was treating a nine-month-old cottonmouth
+    for mites. As I dropped the snake into a sink, it twisted its head and
+    bit the tip of my right middle finger with one fang. The fang entered just
+    under the fingernail and was directed downward, the venom being injected
+    about five millimeters below the site of fang penetration. After placing the
+    snake back in its cage, I squeezed the finger once to promote bleeding, wrapped
+    a string around the base of the finger, and drove to Watkins Memorial Hospital
+    on the University of Kansas campus. I began to feel a burning sensation in the
+    tip of the finger almost immediately. Upon my arrival at the hospital, an additional
+    ligature was placed around my wrist. At 8:30 a.m. a small incision
+    was made in the end of the finger, which by this time was beginning to darken
+    at the point of venom deposition. I sucked on the finger until 8:35 a.m.,
+    when a pan of ice water that I had requested was brought to me. No pain
+    was felt except that caused by the ice. Fresh ice was added as needed to
+    keep the temperature low. By 9:30 a.m. the finger had swollen and stiffened.
+    At 10:00 a.m. the swelling had progressed to the index finger and back of
+    the hand. I experienced difficulty in opening and closing the hand. Blood
+    oozed slowly from the incision. A dull ache persisted and about every two
+    to four minutes a sharp throb could be felt until nearly 11:00 a.m., when the
+    pain diminished. The rate and intensity of throbbing increased whenever the
+    hand was removed from the ice bath for more than a few seconds. Although
+    only the hand was immersed, the entire forearm was cold. Pain was felt along
+    the lymphatics on top of the arm when it was touched, and by 1:00 p.m. a
+    slight pain could be felt in the armpit. Since swelling and pain were almost
+    nonexistent by 2:00 p.m., I was permitted to leave. After walking to a nearby
+    building, I again felt a burning sensation as the hand warmed. I made
+    another ice bath and again immersed the hand in it until 4:10 p.m., at which
+    time it was removed from the water. The pain and swelling began anew, and
+    the hand was placed back in an ice bath from 5:30 p.m. until about 7:30 p.m.
+    At this time cryotherapy was discontinued. From 10:00 p.m. to
+    12:00 midnight my legs twitched periodically, and pain could be felt in both
+    armpits. A slight difficulty in breathing also was experienced for a short time.
+    The acute pain and burning sensation remained in the finger until the following
+    morning, but swelling progressed only as far as the wrist. The only discomfort
+    that day was in the finger. The tip was darkened, the entire first
+    digit red and feverish, and the lymphatics still painful when touched. By the
+    third day the swelling had regressed. The incision itself was the main cause
+    of discomfort, and the soreness at the site of the bite persisted for at least four
+    days.</p>
+<p>Although the L-C method of snakebite treatment has been vigorously attacked
+    by many, there is still need of much more data before it can be unequivocally
+    condemned or praised. It was preferred in the treatment of this
+    bite because: I knew that envenomation was minimal and that there would be
+    no need for antivenin; only one fang of a snake less than one foot long had
+    entered the tip of the finger; the snake had bitten three frogs in the previous <span class="pagenum"><a name="Page_480" id="Page_480">[480]</a></span> two days and had possibly used up a considerable amount of its venom; the
+    venom was deposited at such a shallow depth that at least a portion of it
+    could be removed by suction; and the wound bled freely even before suction
+    was applied. The ice water was uncomfortably cold but was not cold enough
+    to cause frostbite, a major objection to the L-C method. Ideally, fresh ice
+    should be added little by little to replace that which is melting, and the immersed
+    area should be protected from the water by a plastic bag. Pain and
+    swelling can be minimized by cryotherapy, but I would recommend its use
+    only in cases of mild poisoning such as the one described herein.</p>
+<h3>Snakebite in the United States</h3>
+<p>Many estimates have been made of the number of bites of poisonous snakes
+    that occur annually in the United States. The occurrence of poisonous snakebite
+    has been nearly as badly underestimated as fatal results of their envenomations
+    have been overrated. For important data on number of persons bitten
+    by poisonous snakes in the United States, see the following: Allen and
+    Swindell (1948:15); Githens (1935:172); Klauber (1956:811); Parrish (1963);
+    Sowder and Gehres (1963:973); Stimson and Engelhardt (1960:153); Swaroop
+    and Grab (1956:441); Swartzwelder (1950:579); Willson (1908:530); and
+    Wood (1954b:937).</p>
+<p>Judging from estimates made in several states, the number of poisonous
+    snakebites in the United States would be about 5000 per year. In the region
+    where the cottonmouth occurs there are approximately 2000 persons bitten
+    annually by poisonous snakes. Of these approximately 39 per cent are copperhead
+    bites, 30 per cent each are cottonmouth and rattlesnake bites, and I per
+    cent are coral snake bites. These percentages vary considerably from place
+    to place, because of the distribution and abundance of the eight species of
+    poisonous snakes whose ranges overlap that of the cottonmouth.</p>
+<p>According to Parrish (1963), about 14 people die of snakebite each year in
+    the United States. Of these deaths, about 6.6 per cent are attributable to
+    cottonmouths, 77.0 per cent to rattlesnakes, and 1.6 per cent to coral snakes;
+    14.8 per cent are unidentified. Almost half of the fatalities are in persons
+    less than 20 years of age, the high mortality rate being partially due to the
+    greater ratio of venom to body weight.</p>
+<hr class="chap" />
+<h2>SUMMARY</h2>
+<p>In my study, 306 living and preserved cottonmouths were examined.
+    This species occurs throughout the coastal plains of the
+    southeastern United States, usually at altitudes of less than 500 feet
+    but occasionally up to altitudes of more than 2000 feet.</p>
+<p>Two subspecies are recognized: the eastern cottonmouth, <i>A. p.
+    piscivorus</i>, occurring from extreme eastern Mississippi to southeastern
+    Virginia and Florida; and the western cottonmouth, <i>A. p.
+    leucostoma</i>, occurring from eastern Mississippi northward to southern
+    Illinois and Missouri and westward to central Texas. Intergradation
+    occurs in eastern Mississippi.</p>
+<p><span class="pagenum"><a name="Page_481" id="Page_481">[481]</a></span></p>
+<p>The northern edge of the range is probably limited by low temperatures
+    in winter, and the western edge by lack of available
+    habitat resulting from insufficient precipitation. Old records of occurrence
+    indicate that the range has decreased in the last 100 years.
+    The species inhabits mostly areas where water is found, but at times
+    wanders a mile or more from the nearest water.</p>
+<p>The ground color is predominantly a brown, but varies from a
+    brownish-green to almost black with a pattern of 10 to 17 irregular
+    bands of a darker shade of brown. The pattern is better defined in
+    the eastern subspecies than in the western.</p>
+<p>The scutellation resembles that of other species of <i>Agkistrodon</i>.
+    In the specimens examined supralabials ranged from 7 to 9, and
+    infralabials from 8 to 12. The number of dorsal scale rows on the
+    neck, at mid-body, and immediately anterior to the anus is relatively
+    constant at 27-25-21, respectively. Ventral scales of 34 males averaged
+    134.4 (128 to 139), and those of 48 females 133.5 (128 to 137).
+    The number of caudal scales showed some degree of sexual dimorphism;
+    the average was 45.4 (41 to 50) in 34 males and 42.6
+    (39 to 49) in 44 females. In general, caudal scales on the basal
+    half of the tail are undivided, whereas those on the distal half are
+    divided. No marked geographical variation was found in any scale
+    character.</p>
+<p>The poison fangs vary in length from 1.3 per cent of snout-vent
+    length in juveniles to 1.0 per cent in large adults. Fangs of
+    captive cottonmouths were shed and replaced at intervals of about
+    21 days, but the interval was variable. Relationships in distance
+    between the base of fangs and between fang punctures in an actual
+    bite indicate that examination of the wound does not provide a
+    good basis for judging accurately the size of the snake that inflicted
+    the bite.</p>
+<p>In general, females less than 450 millimeters in snout-vent length
+    were juveniles; those more than 450 millimeters were classified as
+    post partum or reproductive on the basis of sizes of ovarian follicles.
+    Since about half the adult females were fecund, it was concluded
+    that a biennial reproductive cycle occurs in this species. An annual
+    cycle may occur in areas where temperature permits year-round
+    activity. It was estimated that females become sexually mature at
+    an age of approximately two and one-half years. Mating is probably
+    most concentrated in early spring at about the time when females
+    ovulate, but copulation is not a stimulus for ovulation. Sperm
+    retention and delayed fertilization allow young to be produced without <span class="pagenum"><a name="Page_482" id="Page_482">[482]</a></span> copulation occurring in each breeding season. The testes increase
+    in size gradually rather than rapidly at maturity or in each
+    breeding season, but seasonal cycles in sperm production occur.</p>
+<p>The gestation period is three and one-half to four months. Determination
+    of sex in the embryos is possible by late June, because
+    the hemipenes of males are evaginated until the time of birth.
+    Parturition generally occurs in August or September, but captivity
+    may delay birth for a month or more. From one to 16 young per
+    litter are born, depending on size of the mother and other factors;
+    but the average is between six and seven. Mortality rate at birth is
+    high in captive individuals but has not been determined in natural
+    populations. The sex ratio in embryos and adults examined revealed
+    about 53 per cent females. Because sufficient information on
+    population composition is not available, an estimate of the percentage
+    of adults in a natural population was based upon the number
+    found in my study. The reproductive potential was estimated
+    from these figures.</p>
+<p>Normal young at birth are 230 to 240 millimeters in snout-vent
+    length, but their size is influenced by the condition of the mother.
+    Comparison of newborn young with those captured in spring
+    indicates that little growth occurs during winter. Early growth is
+    largely dependent upon feeding before winter quiescence.</p>
+<p>The umbilical cord is broken at birth and the navel closes within
+    a few days, but the scar remains throughout life. Sexual dimorphism
+    in the position of the scar is characteristic of some snakes but is
+    minimal in cottonmouths.</p>
+<p>In those snakes more than 700 millimeters in length, males outnumber
+    females three to one. The maximum age of cottonmouths
+    in nature is unknown, but one has been kept in captivity for more
+    than 18 years.</p>
+<p>Allometric growth is striking in cottonmouths. The head and
+    tail are proportionately longer in young individuals than in adults;
+    and in males the tail is, on the average, slightly longer than in
+    females of the same size.</p>
+<p>Shedding of the skin provides for growth and wear in snakes.
+    The young shed within a few days after birth and generally shed
+    more frequently than adults. Frequency of shedding depends
+    mostly on amount of food consumed, and there is some evidence
+    that injuries on the head and neck increase the frequency of shedding.
+    Before shedding, the eyes become cloudy for about five <span class="pagenum"><a name="Page_483" id="Page_483">[483]</a></span> and one-half days, then clear up again for about four days before
+    the skin is shed.</p>
+<p>The food of cottonmouths consists mainly of small vertebrates
+    and occasionally invertebrates that are found near water. Fish,
+    amphibians, and reptiles make up nearly 70 per cent of the diet.
+    Carrion is also eaten and cannibalism occurs occasionally. Food
+    is obtained by lying in ambush or by active searching. The young
+    are known to lure their prey within striking range by waving their
+    yellow tails in a manner suggestive of writhing grubs. The method
+    of obtaining prey differs according to the kind of prey. Generally,
+    cottonmouths retain their hold on fish or frogs but release mice
+    and larger prey after delivering a bite.</p>
+<p>The major causes of mortality of cottonmouths are obscure.
+    Predators are known to include alligators, indigo snakes, king-snakes,
+    largemouth bass, and blue herons; there are probably
+    numerous others. Heavy parasitic infestations were found among
+    the snakes examined. Snake mites, <i>Ophionyssus natricus</i>, became
+    increasingly abundant on almost all captive snakes in April and
+    May of 1963. Lung flukes (<i>Ochetosoma</i> sp.) were in 16 of 20
+    captive snakes, and many preserved specimens contained nematodes
+    (<i>Kalicephalus</i> sp.) in the stomach and/or tapeworms (<i>Ophiotaenia</i> sp.) in the intestine. Although parasitic infestation causes discomfort
+    and may lower resistance to other detrimental factors, it
+    is difficult to attribute death to the effect of any particular kind
+    of parasite. Miscellaneous causes of death of some captive snakes
+    also were discussed.</p>
+<p>The maximal body temperatures tolerated by four cottonmouths
+    were between 38&deg; and 40&deg; C., but a temperature of 38&deg; was lethal
+    to a fifth individual. Cottonmouths have been found on occasion
+    when other snakes were inactive because of low temperatures, but
+    minimal temperatures tolerated by this species are not known. The
+    annual cycle of activity is dependent upon temperature and thus
+    varies from north to south. Cottonmouths generally migrate inland
+    in autumn, usually to dry forested hillsides, where they den along
+    with other species of snakes. After a few warm days in spring
+    they migrate back to the water's edge. The diel activity cycle likewise
+    depends upon temperatures but is influenced by other factors
+    as well. In spring and autumn, the snakes are active mostly on
+    warm, sunny days, whereas in summer they are active mostly at
+    night. In order to maintain adequate internal temperatures, much <span class="pagenum"><a name="Page_484" id="Page_484">[484]</a></span> time is spent basking mostly in a characteristic flat, resting coil
+    either beside a body of water or above water on limbs of dead
+    trees. In this position the snake is ready either for a short strike
+    or a hasty getaway.</p>
+<p>Juveniles appear particularly aggressive and strike repeatedly
+    when approached, a behavioral pattern definitely favoring survival.
+    Adults vary in disposition, usually appearing sluggish and lazy,
+    but they are capable of striking rapidly when disturbed. The typical
+    threat display consists of lying in a coiled position with the mouth
+    opened widely, exposing the white interior, and with the tail vibrating
+    rapidly. The striking posture resembles the resting coil except
+    that the anterior part of the body is raised off the ground and the
+    mouth is sometimes opened. Musk is often ejected in a fine spray
+    from glands in the tail as a further defensive action.</p>
+<p>&quot;Head bobbing,&quot; more properly described as spastic contractions
+    of the body, was observed in captives when food was introduced
+    into a cage containing several individuals or when one of the
+    snakes was returned to the cage after being handled. Reports in
+    the literature also have connected these jerking movements with
+    courtship. The response appears to be elicited whenever a nervous
+    state is recognized in another individual and may serve to protect
+    the jerking individual from aggressive advances of the former.</p>
+<p>The relatively heavy appearance of the body, sluggish habits,
+    and cryptic coloration are correlated with the development of
+    venom and fangs. The poison apparatus has developed primarily
+    as a means of causing rapid death in prey and secondarily, perhaps,
+    to begin the digestion of small animals that are the usual prey, but
+    it is also important as a defensive device. The venom contains at
+    least eight constituents that aid in its action on prey. Toxicity of
+    the venom is difficult to determine because of numerous variables,
+    but cottonmouth venom is generally believed to be less potent
+    than that of most rattlesnakes and more potent than that of the
+    copperhead. Snakes in general are more resistant to snake venoms
+    than other vertebrates of similar size, but there is no immunity
+    even to their own venom.</p>
+<p>About ten per cent of the approximately 5000 bites of poisonous
+    snakes per year in the United States are attributable to cottonmouths,
+    and about seven per cent of the approximately 14 deaths
+    per year are caused by cottonmouths.</p>
+<hr class="chap" />
+<p><span class="pagenum"><a name="Page_485" id="Page_485">[485]</a></span></p>
+<h2><a name="LITERATURE_CITED" id="LITERATURE_CITED"></a>LITERATURE CITED</h2>
+<p><span class="smcap">Allen, E. R.</span></p>
+<blockquote>
+    <p>1937. Florida snake venom experiments. Florida Acad. Sci., 2:7 pp.</p>
+</blockquote>
+<p><span class="smcap">Allen, E. R.</span>, and <span class="smcap">Swindell, D.</span></p>
+<blockquote>
+    <p>1948. Cottonmouth moccasin of Florida. Herpetologica, 4:1-16 (first
+        supplement).</p>
+</blockquote>
+<p><span class="smcap">Allen, M. J.</span></p>
+<blockquote>
+    <p>1932. A survey of the amphibians and reptiles of Harrison County, Mississippi.
+        Amer. Mus. Novit., 542:1-20.</p>
+</blockquote>
+<p><span class="smcap">Anderson, P.</span></p>
+<blockquote>
+    <p>1941. The cottonmouth in northern Missouri.  Copeia, 1941(3):178.</p>
+    <p>1945. New herpetological records for Missouri. Bull. Chicago Acad.
+        Sci., 7(5):271-275.</p>
+</blockquote>
+<p><span class="smcap">Anon.</span></p>
+<blockquote>
+    <p>1953. Snake collecting hobby of Colonial Heights lad. Virginia Wildlife,
+        14-24.</p>
+</blockquote>
+<p><span class="smcap">Auffenberg, W.</span></p>
+<blockquote>
+    <p>1963. The fossil snakes of Florida. Tulane Studies Zool., 10(3):131-216,
+        51 figs.</p>
+</blockquote>
+<p><span class="smcap">Bailey, R. M.</span></p>
+<blockquote>
+    <p>1948. Winter mortality in the snake <i>Storeria dekayi</i>. Copeia, 1948(3):
+        215.</p>
+</blockquote>
+<p><span class="smcap">Barbour, R. W.</span></p>
+<blockquote>
+    <p>1956. A study of the cottonmouth, <i>Agkistrodon piscivorus leucostoma</i> Troost, in Kentucky. Trans. Kentucky Acad. Sci., 17(1):33-41,
+        1 fig.</p>
+</blockquote>
+<p><span class="smcap">Blanchard, F. N.</span></p>
+<blockquote>
+    <p>1922. The amphibians and reptiles of western Tennessee. Occ. Pap.
+        Mus. Zool.; Univ. Michigan, 117:1-18.</p>
+</blockquote>
+<p><span class="smcap">Bogert, C. M.</span></p>
+<blockquote>
+    <p>1943. Dentitional phenomena in cobras and other elapids with notes on
+        adaptive modifications of fangs. Bull. Amer. Mus. Nat. Hist.,
+        81(3):285-360.</p>
+</blockquote>
+<p><span class="smcap">Brattstrom, B. H.</span></p>
+<blockquote>
+    <p>1954. The fossil pitvipers (Reptilia: Crotalidae) of North America.
+        Trans. San Diego Soc. Nat. Hist., 12(3):31-46, 2 figs.</p>
+</blockquote>
+<p><span class="smcap">Brown, A. E.</span></p>
+<blockquote>
+    <p>1903. Texas reptiles and their faunal relations. Proc. Acad. Nat. Sci.
+        Philadelphia, pp. 543-558.</p>
+</blockquote>
+<p><span class="smcap">Carpenter, C. C.</span></p>
+<blockquote>
+    <p>1958. Reproduction, young, eggs, and food of Oklahoma snakes. Herpetologica,
+        14:113-115.</p>
+</blockquote>
+<p><span class="smcap">Carr, A. F., Jr.</span></p>
+<blockquote>
+    <p>1936. The gulf-island cottonmouths. Proc. Florida Acad. Sci., 1:86-90.</p>
+</blockquote>
+<p><span class="smcap">Carr, A. F., Jr.</span>, and <span class="smcap">Carr, M. H.</span></p>
+<blockquote>
+    <p>1942. Notes on the courtship of the cottonmouth moccasin. Proc. New
+        England Zool. Club, July 18, 20:1-6.</p>
+</blockquote>
+<p><span class="smcap">Clark, R. F.</span></p>
+<blockquote>
+    <p>1949. Snakes of the hill parishes of Louisiana. Jour. Tennessee Acad.
+        Sci., 24(4):244-261.</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_486" id="Page_486">[486]</a></span></p>
+<p><span class="smcap">Conant, R.</span></p>
+<blockquote>
+    <p>1933. Three generations of cottonmouths, <i>Agkistrodon piscivorus</i> (Lac&eacute;p&egrave;de).
+        Copeia, 1933(1):43.</p>
+    <p>1934. Two rattlesnakes killed by a cottonmouth. Science, 80(2078):382.</p>
+    <p>1958. A field guide to reptiles and amphibians. Houghton Mifflin Co.,
+        Boston, 366 pp.</p>
+</blockquote>
+<p><span class="smcap">Cook, F. A.</span></p>
+<blockquote>
+    <p>1962. Snakes of Mississippi. Mississippi Game and Fish Comm., Surv.
+        Bull., ii + 45 pp.</p>
+</blockquote>
+<p><span class="smcap">Corrington, J. D.</span></p>
+<blockquote>
+    <p>1929. Herpetology of the Columbia, South Carolina region. Copeia,
+        1929:58-83.</p>
+</blockquote>
+<p><span class="smcap">Cowles, R. B.</span></p>
+<blockquote>
+    <p>1938. Unusual defense postures assumed by rattlesnakes. Copeia,
+        1938(1):13.</p>
+</blockquote>
+<p><span class="smcap">Cowles, R. B.</span>, and <span class="smcap">Bogert, C. M.</span></p>
+<blockquote>
+    <p>1944. A preliminary study of the thermal requirements of desert reptiles.
+        Bull. Amer. Mus. Nat. Hist., 83(5):263-296.</p>
+</blockquote>
+<p><span class="smcap">Criley, B. R.</span></p>
+<blockquote>
+    <p>1956. Development of a multivalent antivenin for the family Crotalidae.
+        Pp. 373-380 <i>in</i> Venoms (ed. Buckley, E. E., and Porges, N., Amer.
+        Assoc. Adv. Sci., Publ. No. 44).</p>
+</blockquote>
+<p><span class="smcap">Darlington, P. J.</span></p>
+<blockquote>
+    <p>1957. Zoogeography: the geographical distribution of animals. John
+        Wiley and Sons, Inc., New York, xi + 675 pp.</p>
+</blockquote>
+<p><span class="smcap">Davis, D. D.</span></p>
+<blockquote>
+    <p>1936. Courtship and mating behavior in snakes. Zool. Series Field Mus.
+        Nat. Hist., 20:257-290, figs. 28-34.</p>
+</blockquote>
+<p><span class="smcap">Didisheim, P.</span>, and <span class="smcap">Lewis, J. H.</span></p>
+<blockquote>
+    <p>1956. Fibrinolytic and coagulent activities of certain snake venoms and
+        proteases. Proc. Soc. Exp. Biol. Med., 93(1):10-13.</p>
+</blockquote>
+<p><span class="smcap">Ditmars, R. L.</span></p>
+<blockquote>
+    <p>1915. The reptile book. Doubleday, Page and Co., Garden City, N. Y.,
+        xxxii + 472 pp.</p>
+    <p>1945. The reptiles of North America. Doubleday, Doran and Co., Inc.,
+        Garden City, N. Y., xvi + 476 pp., 135 pls.</p>
+</blockquote>
+<p><span class="smcap">Dowling, H. G.</span></p>
+<blockquote>
+    <p>1951a. A proposed standard system of counting ventrals in snakes. British
+        Jour. Herp., 1(5):97-98, 1 fig.</p>
+    <p>1951b. A proposed method of expressing scale reductions in snakes.
+        Copeia, 1951(2):131-134.</p>
+</blockquote>
+<p><span class="smcap">Dundee, H. A.</span>, and <span class="smcap">Burger, W. L., Jr.</span></p>
+<blockquote>
+    <p>1948. A denning aggregation of the western cottonmouth. Nat. Hist.
+        Misc., Chicago Acad. Sci., 21:1-2.</p>
+</blockquote>
+<p><span class="smcap">Edgren, R. A.</span></p>
+<blockquote>
+    <p>1951. The umbilical scar, a sexually dimorphic character in <i>Heterodon
+        platyrhinos</i>. Nat. Hist. Misc., 83:1-2.</p>
+</blockquote>
+<p><span class="smcap">Fairley, N. H.</span></p>
+<blockquote>
+    <p>1929. The present position of snake bite and the snake bitten in Australia.
+        Med. Jour. Australia, 1(10):296-313.</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_487" id="Page_487">[487]</a></span></p>
+<p><span class="smcap">Fitch, H. S.</span></p>
+<blockquote>
+    <p>1956. Temperature responses in free-living amphibians and reptiles in
+        northeastern Kansas. Univ. Kansas Publ. Mus. Nat. Hist., 8(7):417-476,
+        10 figs., 6 tables.</p>
+    <p>1960. Autecology of the copperhead. Univ. Kansas Publ. Mus. Nat. Hist.,
+        13(4):85-288, pls. 13-20, 26 figs.</p>
+</blockquote>
+<p><span class="smcap">Force, E. R.</span></p>
+<blockquote>
+    <p>1930. The amphibians and reptiles of Tulsa County, Oklahoma, and
+        vicinity. Copeia, 1930(2):25-39.</p>
+</blockquote>
+<p><span class="smcap">Fox, W.</span></p>
+<blockquote>
+    <p>1948. Effect of temperature on development of scutulation in the garter
+        snake, <i>Thamnophis elegans atratus</i>. Copeia, 1948(4):252-262.</p>
+</blockquote>
+<p><span class="smcap">Githens, T. S.</span></p>
+<blockquote>
+    <p>1935. Studies on the venoms of North American pit vipers. Jour. Immun.,
+        29(2):165-173.</p>
+</blockquote>
+<p><span class="smcap">Glissmeyer, H. R.</span></p>
+<blockquote>
+    <p>1951. Symposium. A snake den in Tooele County, Utah. Egg production
+        of the great basin rattlesnake. Herpetologica, 7(1):24-27.</p>
+</blockquote>
+<p><span class="smcap">Gloyd, H. K.</span></p>
+<blockquote>
+    <p>1933. On the effects of moccasin venom upon a rattlesnake. Science,
+        78(2010):13-14.</p>
+    <p>1934. Studies on the breeding habits and young of the copperhead, <i>Agkistrodon mokasen</i> Beauvois. Papers Michigan Acad. Sci., Arts
+        and Letters, 19:587-604.</p>
+</blockquote>
+<p><span class="smcap">Gloyd, H. K.</span>, and <span class="smcap">Conant, R.</span></p>
+<blockquote>
+    <p>1943. A synopsis of the American forms of <i>Agkistrodon</i> (copperheads and
+        moccasins). Bull. Chicago Acad. Sci., 7(2):147-170, 16 figs.</p>
+</blockquote>
+<p><span class="smcap">Goodman, J. D.</span></p>
+<blockquote>
+    <p>1958. Material ingested by the cottonmouth, <i>Agkistrodon piscivorus</i>, at
+        Reelfoot Lake, Tennessee. Copeia, 1958(2):149.</p>
+</blockquote>
+<p><span class="smcap">Guidry, E. V.</span></p>
+<blockquote>
+    <p>1953. Herpetological notes from southeastern Texas. Herpetologica, 9:49-56.</p>
+</blockquote>
+<p><span class="smcap">Hall, H. H.</span>, and <span class="smcap">Smith, H. M.</span></p>
+<blockquote>
+    <p>1947. Selected records of reptiles and amphibians from southeastern
+        Kansas. Trans. Kansas Acad. Sci., 49(4):447-454.</p>
+</blockquote>
+<p><span class="smcap">Hamilton, W. J., Jr.</span>, and <span class="smcap">Pollack, J. A.</span></p>
+<blockquote>
+    <p>1955. The food of some crotalid snakes from Fort Benning, Georgia.
+        Nat. Hist. Misc., 140:1-4.</p>
+</blockquote>
+<p><span class="smcap">Herald, E. S.</span></p>
+<blockquote>
+    <p>1949. Effects of DDT oil solution upon amphibians and reptiles. Herpetologica,
+        5(6):117-120.</p>
+</blockquote>
+<p><span class="smcap">Hickman, C. P.</span></p>
+<blockquote>
+    <p>1922. A northern record for the water moccasin. Copeia, 1922(106):39.</p>
+</blockquote>
+<p><span class="smcap">Hurter, J. H.</span></p>
+<blockquote>
+    <p>1897. A contribution to the herpetology of Missouri. Trans. Acad. Sci.
+        St. Louis, 7:499-503.</p>
+</blockquote>
+<p><span class="smcap">Jacques, R.</span></p>
+<blockquote>
+    <p>1956. The hyaluronidase content of animal venoms. Pp. 291-293 <i>in</i> Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv.
+        Sci., Publ. No. 44).</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_488" id="Page_488">[488]</a></span></p>
+<p><span class="smcap">Keegan, H. L.</span>, and <span class="smcap">Andrews, T. F.</span></p>
+<blockquote>
+    <p>1942. Effects of crotalid venom on North American snakes. Copeia,
+        1942:251-254.</p>
+</blockquote>
+<p><span class="smcap">Kellogg, R.</span></p>
+<blockquote>
+    <p>1925. Poisonous snakes of the United States. U. S. D. A. Papers (371),
+        13 pp.</p>
+</blockquote>
+<p><span class="smcap">Klauber, L. M.</span></p>
+<blockquote>
+    <p>1941. Four papers on the application of statistical methods to herpetological
+        problems. Bull. Zool. Soc. San Diego, 17:1-95.</p>
+    <p>1956. Rattlesnakes. Univ. California Press, 2 vols., xxix + 1476 pp.</p>
+</blockquote>
+<p><span class="smcap">Klimstra, W. D.</span></p>
+<blockquote>
+    <p>1959. Food habits of the cottonmouth in southern Illinois. Chicago Acad.
+        Sci., Nat. Hist. Misc., 168:1-8.</p>
+</blockquote>
+<p><span class="smcap">Laughlin, H. E.</span></p>
+<blockquote>
+    <p>1959. Stomach contents of some aquatic snakes from Lake McAlester,
+        Pittsburgh County, Oklahoma. Texas Jour. Sci., 11(1):83-85.</p>
+</blockquote>
+<p><span class="smcap">Lederer, G.</span></p>
+<blockquote>
+    <p>1931. Aus meinem Tagebuch. Wachenschrift fur Aquar. und Terr'kde.,
+        28:651-653.</p>
+</blockquote>
+<p><span class="smcap">Lee, H. T.</span></p>
+<blockquote>
+    <p>1964. Letters to the Editor, Texas Game and Fish Mag., 22(3):32.</p>
+</blockquote>
+<p><span class="smcap">Lowe, C. H., Jr.</span></p>
+<blockquote>
+    <p>1948. Territorial behavior in snakes and the so-called courtship dance.
+        Herpetologica, 4(4):129-145.</p>
+</blockquote>
+<p><span class="smcap">Mansueti, R.</span></p>
+<blockquote>
+    <p>1946. Mating of the pilot blacksnake. Herpetologica, 3:98-100, 1 fig.</p>
+</blockquote>
+<p><span class="smcap">Martin, J. R.</span>, and <span class="smcap">Wood, J. T.</span></p>
+<blockquote>
+    <p>1955. Notes on the poisonous snakes of the Dismal Swamp area. Herpetologica,
+        11(3):237-238.</p>
+</blockquote>
+<p><span class="smcap">McCollough, N. C.</span>, and <span class="smcap">Gennaro, J. F., Jr.</span></p>
+<blockquote>
+    <p>1963. Evaluation of venomous snake bite in the southern United States
+        from parallel clinical and laboratory investigations. Jour. Florida
+        Med. Assn., 49(12):959-967.</p>
+</blockquote>
+<p><span class="smcap">McIlhenny, E. A.</span></p>
+<blockquote>
+    <p>1935. The alligator's life history. The Christopher Publ. House, Boston,
+        Massachusetts, 117 pp.</p>
+</blockquote>
+<p><span class="smcap">Minton, S. A., Jr.</span></p>
+<blockquote>
+    <p>1953. Variation in venom samples from copperheads (<i>Agkistrodon contortrix
+        mokeson</i>) and timber rattlesnakes (<i>Crotalus horridus horridus</i>).
+        Copeia, 1953:212-215.</p>
+    <p>1954. Polyvalent antivenin in the treatment of experimental snake venom
+        poisoning. Amer. Jour. Trop. Med. and Hyg., 3:1077-1082.</p>
+    <p>1956. Some properties of North American pit viper venoms and their
+        correlation with phylogeny. Pp. 145-151 <i>in</i> Venoms (ed. Buckley,
+        E. E., and Porges, N., Amer. Assoc. Adv. Sci., Publ. No. 44).</p>
+</blockquote>
+<p><span class="smcap">Munro, D. F.</span></p>
+<blockquote>
+    <p>1949. Effect of DDT powder on small cottonmouths. Herpetologica,
+        5:71-72.</p>
+    <p>1950. Additional observations on head bobbing by snakes. Herpetologica,
+        6:88.</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_489" id="Page_489">[489]</a></span></p>
+<p><span class="smcap">Neill, W. T.</span></p>
+<blockquote>
+    <p>1947. Size and habits of the cottonmouth moccasin.  Herpetologica,
+        3:203-205.</p>
+    <p>1949. Head bobbing, a widespread habit of snakes.  Herpetologica,
+        5:114-115.</p>
+    <p>1960. The caudal lure of various juvenile snakes. Quart. Jour. Florida
+        Acad. Sci., 23(3):173-200, 2 figs.</p>
+</blockquote>
+<p><span class="smcap">Neill, W. T.</span>, and <span class="smcap">Allen, E. R.</span></p>
+<blockquote>
+    <p>1955. Metachrosis in snakes. Quart. Jour. Florida Acad. Sci., 18(3):207-215.</p>
+</blockquote>
+<p><span class="smcap">Netting, M. G.</span></p>
+<blockquote>
+    <p>1929. The venom of <i>Sistrurus catenatus</i>. Bull. Antivenin Inst. Amer.,
+        2(4):108-109.</p>
+</blockquote>
+<p><span class="smcap">Parrish, H. M.</span></p>
+<blockquote>
+    <p>1959. Poisonous snakebites resulting in lack of venom poisoning. Virginia
+        Med. Month, 86:396-401.</p>
+    <p>1963. Analysis of 460 fatalities from venomous animals in the United
+        States. Amer. Jour. Med. Sci., 245(2):35-47.</p>
+</blockquote>
+<p><span class="smcap">Parrish, H. M.</span>, and <span class="smcap">Pollard, C. B.</span></p>
+<blockquote>
+    <p>1959. Effects of repeated poisonous snakebite in man. Amer. Jour. Med.
+        Sci., 237(3):277-286.</p>
+</blockquote>
+<p><span class="smcap">Penn, G. H.</span></p>
+<blockquote>
+    <p>1943. Herpetological notes from Cameron Parish, Louisiana. Copeia,
+        1943(1):58-59.</p>
+</blockquote>
+<p><span class="smcap">Perkins, C. B.</span></p>
+<blockquote>
+    <p>1955. Longevity of snakes in captivity in the United States. Copeia,
+        1955(3):262.</p>
+</blockquote>
+<p><span class="smcap">Pope, C. H.</span>, and <span class="smcap">Perkins, R. M.</span></p>
+<blockquote>
+    <p>1944. Differences in the patterns of bites of venomous and of harmless
+        snakes. Archives of Surgery, 49:331-336.</p>
+</blockquote>
+<p><span class="smcap">Rahn, H.</span></p>
+<blockquote>
+    <p>1942. The reproductive cycle of the prairie rattler. Copeia, 1942(4):233-240.</p>
+</blockquote>
+<p><span class="smcap">Ramsey, L. W.</span></p>
+<blockquote>
+    <p>1948. Combat dance and range extension of <i>Agkistrodon piscivorus
+        leucostoma</i>. Herpetologica, 4:228.</p>
+</blockquote>
+<p><span class="smcap">Richmond, M. D.</span></p>
+<blockquote>
+    <p>1952. Head bobbing in reptiles. Herpetologica, 8:38.</p>
+</blockquote>
+<p><span class="smcap">Rosenfeld, S.</span>, and <span class="smcap">Glass, S.</span></p>
+<blockquote>
+    <p>1940. The inhibiting effect of snake bloods upon the hemorrhagic action
+        of viper venoms on mice. Amer. Jour. Med. Sci., 199:482-486.</p>
+</blockquote>
+<p><span class="smcap">Schmidt, K. P.</span></p>
+<blockquote>
+    <p>1946. On the zoogeography of the Holarctic region.  Copeia, 1946:144-152.</p>
+</blockquote>
+<p><span class="smcap">Shaw, C. E.</span></p>
+<blockquote>
+    <p>1948. The male combat &quot;dance&quot; of some crotalid snakes. Herpetologica,
+        4:137-145.</p>
+    <p>1951. Male combat in American colubrid snakes with remarks on combat
+        in other colubrid and elapid snakes. Herpetologica, 7(4):149-168.</p>
+</blockquote>
+<p><span class="smcap">Smith, H. M.</span></p>
+<blockquote>
+    <p>1956. Handbook of amphibians and reptiles of Kansas. 2nd Edition.
+        Univ. Kansas Mus. Nat. Hist., Misc. Publ., 9:1-356, 253 figs.</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_490" id="Page_490">[490]</a></span></p>
+<p><span class="smcap">Smith, H. M.</span>, and <span class="smcap">Buechner, H. K.</span></p>
+<blockquote>
+    <p>1947. The influence of the Balcones Escarpment on the distribution of
+        amphibians and reptiles in Texas. Bull. Chicago Acad. Sci.,
+        pp. 1-16.</p>
+</blockquote>
+<p><span class="smcap">Smith, P. W.</span></p>
+<blockquote>
+    <p>1961. The amphibians and reptiles of Illinois. Illinois Nat. Hist. Survey,
+        28(1):1-298.</p>
+</blockquote>
+<p><span class="smcap">Smith, P. W.</span>, and <span class="smcap">List, J. C.</span></p>
+<blockquote>
+    <p>1955. Notes on Mississippi amphibians and reptiles. Amer. Midl. Nat.,
+        53(1):115-125.</p>
+</blockquote>
+<p><span class="smcap">Sowder, W. T.</span>, and <span class="smcap">Gehres, G. W.</span></p>
+<blockquote>
+    <p>1963. Snakebites in Florida. Jour. Florida Med. Assn., 49(12):973-976.</p>
+</blockquote>
+<p><span class="smcap">Stabler, R. M.</span></p>
+<blockquote>
+    <p>1951. Some observations on two cottonmouth moccasins made during 12
+        and 14 years of captivity. Herpetologica, 7:89-92.</p>
+</blockquote>
+<p><span class="smcap">Stahnke, H. M.</span></p>
+<blockquote>
+    <p>1953. The L-C treatment of venomous bites and stings. Amer. Jour.
+        Trop. Med. and Hyg., 2(1):142-143.</p>
+    <p>1954. The L-C method of treating venomous bites and stings. Pois.
+        Anim. Res. Lab., Arizona State Coll., 28 pp.</p>
+</blockquote>
+<p><span class="smcap">Stejneger, L.</span></p>
+<blockquote>
+    <p>1895. The poisonous snakes of North America. Smithsonian Inst., U. S.
+        Nat. Mus., 1893:337-487, pls. 1-19, figs. 1-70.</p>
+</blockquote>
+<p><span class="smcap">Stimson, A. C.</span>, and <span class="smcap">Engelhardt, T. H.</span></p>
+<blockquote>
+    <p>1960. The treatment of snakebite. Jour. Occ. Med., 2(4):163-168.</p>
+</blockquote>
+<p><span class="smcap">Sutherland, I. D.</span></p>
+<blockquote>
+    <p>1958. The &quot;combat dance&quot; of the timber rattlesnake. Herpetologica,
+        14(1):23-24.</p>
+</blockquote>
+<p><span class="smcap">Swanson, P. L.</span></p>
+<blockquote>
+    <p>1946. Effects of snake venoms on snakes. Copeia, 1946(4):242-249.</p>
+</blockquote>
+<p><span class="smcap">Swaroop, S.</span>, and <span class="smcap">Grab, B.</span></p>
+<blockquote>
+    <p>1956. The snakebite mortality problem in the world. Pp. 439-466 <i>in</i> Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv.
+        Sci., Publ. No. 44).</p>
+</blockquote>
+<p><span class="smcap">Swartzwelder, J. C.</span></p>
+<blockquote>
+    <p>1950. Snake-bite accidents in Louisiana with data on 306 cases. Amer.
+        Jour. Trop. Med., 30(4):575-589.</p>
+</blockquote>
+<p><span class="smcap">Tinkle, D. W.</span></p>
+<blockquote>
+    <p>1962. Reproductive potential and cycles in female <i>Crotalus atrox</i> from
+        northwestern Texas. Copeia, 1962(2):306-313.</p>
+</blockquote>
+<p><span class="smcap">Trowbridge, A. H.</span></p>
+<blockquote>
+    <p>1937. Ecological observations on amphibians and reptiles collected in
+        southeastern Oklahoma during the summer of 1934. Amer. Midl.
+        Nat., 18(2):285-303.</p>
+</blockquote>
+<p><span class="smcap">Vols&oslash;e, H.</span></p>
+<blockquote>
+    <p>1944. Structure and seasonal variation of the male reproductive organs
+        in <i>Vipera berus</i> (L.). Spolia Zool. Mus. Hauniensis V. Reprint,
+        Copenhagen, pp. 1-172.</p>
+</blockquote>
+<p><span class="smcap">Wharton, C. H.</span></p>
+<blockquote>
+    <p>1960. Birth and behavior of a brood of cottonmouths, <i>Agkistrodon piscivorus
+        piscivorus</i>, with notes on tail-luring. Herpetologica, 16:125-129.</p>
+</blockquote>
+<p><span class="pagenum"><a name="Page_491" id="Page_491">[491]</a></span></p>
+<p><span class="smcap">Willson, P.</span></p>
+<blockquote>
+    <p>1908. Snake poisoning in the United States: a study based on an
+        analysis of 740 cases. Arch. Int. Med., 1(5):516-570.</p>
+</blockquote>
+<p><span class="smcap">Wolff, N. O.</span>, and <span class="smcap">Githens, T. S.</span></p>
+<blockquote>
+    <p>1939a. Record venom extraction from water moccasin. Copeia, 1939(1):52.</p>
+    <p>1939b. Yield and toxicity of venom from snakes extracted over a period of
+        two years. Copeia, 1939(4):234.</p>
+</blockquote>
+<p><span class="smcap">Wood, J. T.</span></p>
+<blockquote>
+    <p>1954a. The distribution of poisonous snakes in Virginia. Virginia Jour.
+        Sci., 5(3):152-167, 4 maps.</p>
+    <p>1954b. A survey of 200 cases of snake-bite in Virginia. Amer. Jour. Trop.
+        Med. and Hyg., 3(5):936-943.</p>
+</blockquote>
+<p><span class="smcap">Wood, J. T.</span>, <span class="smcap">Hoback, W. W.</span>, and <span class="smcap">Green, T. W.</span></p>
+<blockquote>
+    <p>1955. Treatment of snake venom poisoning with ACTH and cortisone.
+        Virginia Med. Month, 82:130-135.</p>
+</blockquote>
+<p><span class="smcap">Wright, A. H.</span>, and <span class="smcap">Wright, A. A.</span></p>
+<blockquote>
+    <p>1957. Handbook of snakes of the United States and Canada. Comstock
+        Publ. Assoc., Cornell Univ. Press, 2:ix + 565-1106 pp.</p>
+</blockquote>
+<p><span class="smcap">Yamaguti, S.</span></p>
+<blockquote>
+    <p>1958. Systema helminthum. Interscience Publ., Inc., New York, 3 vols.,
+        5 parts, 1:xi + 1575 pp., 2:vii + 860 pp., 3:1261 pp.</p>
+</blockquote>
+<p><span class="smcap">Yerger, R. W.</span></p>
+<blockquote>
+    <p>1953. Yellow bullhead preyed upon by cottonmouth moccasin. Copeia,
+        1953(2):115.</p>
+</blockquote>
+<p> <i>Transmitted June 20, 1966.</i></p>
+<hr class="chap" />
+<p> <br />
+</p>
+<h2><a name="UNIVERSITY_OF_KANSAS_PUBLICATIONS" id="UNIVERSITY_OF_KANSAS_PUBLICATIONS"></a>UNIVERSITY OF KANSAS PUBLICATIONS
+    MUSEUM OF NATURAL HISTORY</h2>
+<p>Institutional libraries interested in publications exchange may obtain this
+    series by addressing the Exchange Librarian, University of Kansas Library,
+    Lawrence, Kansas. Copies for individuals, persons working in a particular
+    field of study, may be obtained by addressing instead the Museum of Natural
+    History, University of Kansas, Lawrence, Kansas. When copies are requested
+    from the Museum, 25 cents should be included (for each 100 pages or part
+    thereof) for the purpose of defraying the costs of wrapping and mailing. For
+    certain longer papers an additional amount indicated below, toward the cost
+    of production, is to be included. Materials published to date in this series
+    are as follows.</p>
+<p> * An asterisk designates those numbers of which the Museum's supply (not necessarily<br />
+    the Library's supply) is exhausted.  Materials published to date, in this series, are as<br />
+    follows:<br />
+    <br />
+    Vol. 1.  Nos. 1-26 and index. Pp. 1-638, 1946-1950.<br />
+    <br />
+    *Vol. 2.  (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. 1-444, 140 figures in text. April 9, 1948.<br />
+    <br />
+    *Vol. 3.  Nos. 1-4 and index. Pp. 1-681. 1951.<br />
+    <br />
+    *Vol. 4.  (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41 plates, 31 figures in text. December 27, 1951.<br />
+    <br />
+    Vol. 5.  Nos. 1-37 and index. Pp. 1-676, 1951-1953.<br />
+    <br />
+    *Vol. 6.  (Complete)  Mammals of Utah, <i>taxonomy and distribution</i>.  By Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables. August 10, 1952.<br />
+    <br />
+    Vol. 7.  Nos. 1-15 and index. Pp. 1-651, 1952-1955.<br />
+    <br />
+    Vol. 8.  Nos. 1-10 and index. Pp. 1-675, 1954-1956.<br />
+    <br />
+    Vol. 9.  Nos. 1-23 and index. Pp. 1-690, 1955-1960.<br />
+    <br />
+    Vol. 10. Nos. 1-10 and index. Pp. 1-626, 1956-1960.<br />
+    <br />
+    Vol. 11. Nos. 1-10 and index. Pp. 1-703, 1958-1960.<br />
+    <br />
+    Vol. 12.&nbsp; *1. Functional morphology of three bats: Eumops, Myotis, Macrotus. By Terry<br />
+    <span style="margin-left: 6em;">A. Vaughan. Pp. 1-153, 4 plates, 24 figures in text. July 8, 1959.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">*2. The ancestry of modern Amphibia: a review of the evidence. By Theodore</span><br />
+    <span style="margin-left: 6em;">H. Eaton, Jr.&nbsp; Pp. 155-180, 10 figures in text. July 10, 1959.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. The baculum in microtine rodents. By Sydney Anderson. Pp. 181-216, 49</span><br />
+    <span style="margin-left: 6em;">figures in text. February 19, 1960.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">*4. A new order of fishlike Amphibia from the Pennsylvanian of Kansas. By</span><br />
+    <span style="margin-left: 6em;">Theodore H. Eaton, Jr., and Peggy Lou Stewart. Pp. 217-240, 12 figures in</span><br />
+    <span style="margin-left: 6em;">text. May 2, 1960.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. Natural history of the Bell Vireo. By Jon C. Barlow. Pp. 241-296, 6 figures</span><br />
+    <span style="margin-left: 6em;">in text. March 7, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">6. Two new pelycosaurs from the lower Permian of Oklahoma. By Richard C.</span><br />
+    <span style="margin-left: 6em;">Fox. Pp. 297-307, 6 figures in text. May 21, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">7. Vertebrates from the barrier island of Tamaulipas, M&eacute;xico. By Robert K.</span><br />
+    <span style="margin-left: 6em;">Selander, Richard F. Johnston, B. J. Wilks, and Gerald G. Raun. Pp. 309-345,</span><br />
+    <span style="margin-left: 6em;">plates 5-8. June 18, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">8. Teeth of edestid sharks. By Theodore H. Eaton, Jr. Pp. 347-362, 10 figures</span><br />
+    <span style="margin-left: 6em;">in text. October 1, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">9. Variation in the muscles and nerves of the leg in two genera of grouse</span><br />
+    <span style="margin-left: 6em;">(Tympanuchus and Pedioecetes). By E. Bruce Holmes. Pp. 363-474, 20</span><br />
+    <span style="margin-left: 6em;">figures. October 25, 1962. $1.00.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">10. A new genus of Pennsylvanian fish (Crossopterygii, Coelacanthiformes) from</span><br />
+    <span style="margin-left: 6em;">Kansas. By Joan Echols. Pp. 475-501, 7 figures. October 25, 1963.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">11. Observations on the Mississippi Kite in southwestern Kansas. By Henry S.</span><br />
+    <span style="margin-left: 6em;">Fitch. Pp. 503-519. October 25, 1963.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">12. Jaw musculature of the Mourning and White-winged doves. By Robert L.</span><br />
+    <span style="margin-left: 6em;">Merz. Pp. 521-551, 22 figures. October 25, 1963.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">13. Thoracic and coracoid arteries in two families of birds, Columbidae and</span><br />
+    <span style="margin-left: 6em;">Hirundinidae. By Marion Anne Jenkinson. Pp. 553-573, 7 figures. March</span><br />
+    <span style="margin-left: 6em;">2, 1964.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">14. The breeding birds of Kansas. By Richard F. Johnston. Pp. 575-655, 10</span><br />
+    <span style="margin-left: 6em;">figures. May 18, 1964. 75 cents.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">15. The adductor muscles of the jaw in some primitive reptiles. By Richard C.</span><br />
+    <span style="margin-left: 6em;">Fox. Pp. 657-680, 11 figures in text. May 18, 1964.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">Index. Pp. 681-694.</span><br />
+    <br />
+    Vol. 13.  1. Five natural hybrid combinations in minnows (Cyprinidae). By Frank B.<br />
+    <span style="margin-left: 6em;">Cross and W. L. Minckley. Pp. 1-18. June 1, 1960.</span><br />
+    <br />
+    <span style="margin-left: 4em;">2. A distributional study of the amphibians of the Isthmus of Tehuantepec,</span><br />
+    <span style="margin-left: 6em;">M&eacute;xico. By William E. Duellman. Pp. 19-72, plates 1-8, 3 figures in text.</span><br />
+    <span style="margin-left: 6em;">August 16, 1960. 50 cents.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. A new subspecies of the slider turtle (Pseudemys scripta) from Coahuila,</span><br />
+    <span style="margin-left: 6em;">M&eacute;xico.&nbsp; By John M. Legler.&nbsp; Pp. 73-84, plates 9-12, 3 figures in text.</span><br />
+    <span style="margin-left: 6em;">August 16, 1960.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">*4. Autecology of the copperhead. By Henry S. Fitch. Pp. 85-288, plates 13-20,</span><br />
+    <span style="margin-left: 6em;">26 figures in text. November 30, 1960.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. Occurrence of the garter snake, Thamnophis sirtalis, in the Great Plains and</span><br />
+    <span style="margin-left: 6em;">Rocky Mountains. By Henry S. Fitch and T. Paul Maslin. Pp. 289-308,</span><br />
+    <span style="margin-left: 6em;">4 figures in text. February 10, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">6. Fishes of the Wakarusa River in Kansas. By James E. Deacon and Artie L.</span><br />
+    <span style="margin-left: 6em;">Metcalf. Pp. 309-322, 1 figure in text. February 10, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">7. Geographic variation in the North American cyprinid fish, Hybopsis gracilis.</span><br />
+    <span style="margin-left: 6em;">By Leonard J. Olund and Frank B. Cross. Pp. 323-348, plates 21-24, 2</span><br />
+    <span style="margin-left: 6em;">figures in text. February 10, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">8. Descriptions of two species of frogs, genus Ptychohyla; studies of American</span><br />
+    <span style="margin-left: 6em;">hylid frogs, V. By William E. Duellman. Pp. 349-357, plate 25, 2</span><br />
+    <span style="margin-left: 6em;">figures in text. April 27, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">9. Fish populations, following a drought, in the Neosho and Marais des Cygnes</span><br />
+    <span style="margin-left: 6em;">rivers of Kansas. By James Everett Deacon. Pp. 359-427, plates 26-30,</span><br />
+    <span style="margin-left: 6em;">3 figures. August 11, 1961. 75 cents.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">10. Recent soft-shelled turtles of North America (family Trionychidae).&nbsp; By</span><br />
+    <span style="margin-left: 6em;">Robert G. Webb. Pp. 429-611, plates 31-54, 24 figures in text. February</span><br />
+    <span style="margin-left: 6em;">16, 1962.&nbsp; $2.00.</span><br />
+    <br />
+    <span style="margin-left: 4em;">Index. Pp. 613-624.</span><br />
+    <br />
+    Vol. 14.  1. Neotropical bats from western M&eacute;xico.  By Sydney Anderson.  Pp. 1-8.<br />
+    <span style="margin-left: 6em;">October 24, 1960.</span><br />
+    <br />
+    <span style="margin-left: 4em;">2. Geographic variation in the harvest mouse, Reithrodontomys megalotis, on</span><br />
+    <span style="margin-left: 6em;">the central Great Plains and in adjacent regions.&nbsp; By J. Knox Jones, Jr.,</span><br />
+    <span style="margin-left: 6em;">and B. Mursaloglu. Pp. 9-27, 1 figure in text. July 24, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. Mammals of Mesa Verde National Pork, Colorado. By Sydney Anderson.</span><br />
+    <span style="margin-left: 6em;">Pp. 29-67, plates 1 and 2, 3 figures in text. July 24, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">4. A new subspecies of the black myotis (bat) from eastern Mexico. By E.</span><br />
+    <span style="margin-left: 6em;">Raymond Hall and Ticul Alvarez. Pp. 69-72, 1 figure in text. December</span><br />
+    <span style="margin-left: 6em;">29, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. North American yellow bats, &quot;Dasypterus,&quot; and a list of the named kinds</span><br />
+    <span style="margin-left: 6em;">of the genus Lasiurus Gray. By E. Raymond Hall and J. Knox Jones, Jr.</span><br />
+    <span style="margin-left: 6em;">Pp. 73-98, 4 figures in text. December 29, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">6. Natural history of the brush mouse (Peromyscus boylii) in Kansas with</span><br />
+    <span style="margin-left: 6em;">description of a new subspecies. By Charles A. Long. Pp. 99-111, 1 figure</span><br />
+    <span style="margin-left: 6em;">in text. December 29, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">7. Taxonomic status of some mice of the Peromyscus boylii group in eastern</span><br />
+    <span style="margin-left: 6em;">Mexico, with description of a new subspecies. By Ticul Alvarez. Pp. 113-120,</span><br />
+    <span style="margin-left: 6em;">1 figure in text. December 29, 1961.</span><br />
+    <br />
+    <span style="margin-left: 4em;">8. A new subspecies of ground squirrel (Spermophilus spilosoma) from Tamaulipas,</span><br />
+    <span style="margin-left: 6em;">Mexico. By Ticul Alvarez. Pp. 121-124. March 7, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">9. Taxonomic status of the free-tailed bat, Tadarida yucatanica Miller. By J.</span><br />
+    <span style="margin-left: 6em;">Knox Jones, Jr., and Ticul Alvarez. Pp. 125-133, 1 figure in text. March 7,</span><br />
+    <span style="margin-left: 6em;">1962.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">10. A new doglike carnivore, genus Cynaretus, from the Clarendonian Pliocene,</span><br />
+    <span style="margin-left: 6em;">of Texas. By E. Raymond Hall and Walter W. Dalquest. Pp. 135-138,</span><br />
+    <span style="margin-left: 6em;">2 figures in text. April 30, 1962.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">11. A new subspecies of wood rat (Neotoma) from northeastern Mexico. By</span><br />
+    <span style="margin-left: 6em;">Ticul Alvarez. Pp. 139-143, April 30, 1962.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">12. Noteworthy mammals from Sinaloa, Mexico. By J. Knox Jones, Jr., Ticul</span><br />
+    <span style="margin-left: 6em;">Alvarez, and M. Raymond Lee. Pp. 145-159. 1 figure in text. May 18,</span><br />
+    <span style="margin-left: 6em;">1962.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">13. A new bat (Myotis) from Mexico. By E. Raymond Hall. Pp. 161-164,</span><br />
+    <span style="margin-left: 6em;">1 figure in text. May 21, 1962.</span><br />
+    <br />
+    <span style="margin-left: 3em;">*14. The mammals of Veracruz. By E. Raymond Hall and Walter W. Dalquest.</span><br />
+    <span style="margin-left: 6em;">Pp. 165-362, 2 figures. May 20, 1963. $2.00.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">15. The recent mammals of Tamaulipas, M&eacute;xico. By Ticul Alvarez. Pp. 363-473,</span><br />
+    <span style="margin-left: 6em;">5 figures in text. May 20, 1963. $1.00.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">16. A new subspecies of the fruit-eating bat, Sturnira ludovici, from western</span><br />
+    <span style="margin-left: 6em;">Mexico. By J. Knox Jones, Jr., and Gary L. Phillips. Pp. 475-481, 1 figure</span><br />
+    <span style="margin-left: 6em;">in text. March 2, 1964.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">17. Records of the fossil mammal Sinclairella, Family Apatemyidae, from the</span><br />
+    <span style="margin-left: 6em;">Chadronian and Orellan. By William A. Clemens. Pp. 483-491. 2 figures</span><br />
+    <span style="margin-left: 6em;">in text. March 2, 1964.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">18. The mammals of Wyoming. By Charles A. Long. Pp. 493-758, 82 figs.</span><br />
+    <span style="margin-left: 6em;">July 6, 1965. $3.00.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">Index. Pp. 759-784.</span><br />
+    <br />
+    Vol. 15.  1. The amphibians and reptiles of Michoac&aacute;n, M&eacute;xico. By William E. Duellman.<br />
+    <span style="margin-left: 6em;">Pp. 1-148, plates 1-6, 11 figures in text. December 20, 1961. $1.50.</span><br />
+    <br />
+    <span style="margin-left: 4em;">2. Some reptiles and amphibians from Korea. By Robert G. Webb, J. Knox</span><br />
+    <span style="margin-left: 6em;">Jones, Jr., and George W. Byers. Pp. 149-173. January 31, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. A new species of frog (Genus Tomodactylus) from western M&eacute;xico. By</span><br />
+    <span style="margin-left: 6em;">Robert G. Webb. Pp. 175-181, 1 figure in text. March 7, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">4. Type specimens of amphibians and reptiles in the Museum of Natural History,</span><br />
+    <span style="margin-left: 6em;">the University of Kansas. By William E. Duellman and Barbara Berg.</span><br />
+    <span style="margin-left: 6em;">Pp. 183-204. October 26, 1962.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. Amphibians and Reptiles of the Rainforests of Southern El Pet&eacute;n, Guatemala.</span><br />
+    <span style="margin-left: 6em;">By William E. Duellman. Pp. 205-249, plates 7-10, 6 figures in text. October</span><br />
+    <span style="margin-left: 6em;">4, 1963.</span><br />
+    <br />
+    <span style="margin-left: 4em;">6. A revision of snakes of the genus Conophis (Family Colubridae, from Middle</span><br />
+    <span style="margin-left: 6em;">America). By John Wellman. Pp. 251-295, 9 figures in text. October 4,</span><br />
+    <span style="margin-left: 6em;">1963.</span><br />
+    <br />
+    <span style="margin-left: 4em;">7. A review of the Middle American tree frogs of the genus Ptychohyla. By</span><br />
+    <span style="margin-left: 6em;">William E. Duellman. Pp. 297-349, plates 11-18, 7 figures in text. October</span><br />
+    <span style="margin-left: 6em;">18, 1963. 50 cents.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">*8. Natural history of the racer Coluber constrictor. By Henry S. Fitch. Pp.</span><br />
+    <span style="margin-left: 6em;">351-468, plates 19-22, 20 figures in text. December 30, 1963. $1.00.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">9. A review of the frogs of the Hyla bistincta group. By William E. Duellman.</span><br />
+    <span style="margin-left: 6em;">Pp. 469-491, 4 figures in text. March 2, 1964.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">10. An ecological study of the garter snake, Thamnophis sirtalis. By Henry S.</span><br />
+    <span style="margin-left: 6em;">Fitch. Pp. 493-564, plates 23-25, 14 figures in text. May 17, 1965.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">11. Breeding cycle in the ground skink, Lygosoma laterale. By Henry S. Fitch</span><br />
+    <span style="margin-left: 6em;">and Harry W. Greene. Pp. 565-575, 3 figures in text. May 17, 1965.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">12. Amphibians and reptiles from the Yucatan Peninsula, M&eacute;xico. By William</span><br />
+    <span style="margin-left: 6em;">E. Duellman. Pp. 577-614, 1 figure in text. June 22, 1965.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">13. A new species of turtle, Genus Kinosternon, from Central America, by John</span><br />
+    <span style="margin-left: 6em;">M. Legler. Pp. 615-625, pls. 26-28, 2 figures in text. July 20, 1965.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">14. A biogeographic account of the herpetofauna of Michoac&aacute;n, M&eacute;xico. By</span><br />
+    <span style="margin-left: 6em;">William E. Duellman. Pp. 627-709, pls. 29-36, 5 figures in text. December</span><br />
+    <span style="margin-left: 6em;">30, 1965.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">15. Amphibians and reptiles of Mesa Verde National Park, Colorado. By Charles</span><br />
+    <span style="margin-left: 6em;">L. Douglas. Pp. 711-744, pls. 37, 38, 6 figures in text. March 7, 1966.</span><br />
+    <br />
+    <span style="margin-left: 3.5em;">Index. Pp. 745-770.</span><br />
+    <br />
+    Vol. 16.  1. Distribution and taxonomy of Mammals of Nebraska. By J. Knox Jones, Jr.<br />
+    <span style="margin-left: 6em;">Pp. 1-356, pls. 1-4, 82 figures in text. October 1, 1964. $3.50.</span><br />
+    <br />
+    <span style="margin-left: 4em;">2. Synopsis of the lagomorphs and rodents of Korea. By J. Knox Jones, Jr.,</span><br />
+    <span style="margin-left: 6em;">and David H. Johnson. Pp. 357-407. February 12, 1965.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. Mammals from Isla Cozumel, Mexico, with description of a new species of</span><br />
+    <span style="margin-left: 6em;">harvest mouse. By J. Knox Jones, Jr., and Timothy E. Lawlor. Pp. 409-419,</span><br />
+    <span style="margin-left: 6em;">1 figure in text. April 13, 1965.</span><br />
+    <br />
+    <span style="margin-left: 4em;">4. The Yucatan deer mouse, Peromyscus yucatanicus. By Timothy E. Lawlor.</span><br />
+    <span style="margin-left: 6em;">Pp. 421-438, 2 figures in text. July 20, 1965.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. Bats from Guatemala. By J. Knox Jones, Jr. Pp. 439-472. April 18, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">More numbers will appear in volume 16.</span><br />
+    <br />
+    Vol. 17.  1. Localities of fossil vertebrates obtained from the Niobrara Formation (Cretaceous)<br />
+    <span style="margin-left: 6em;">of Kansas. By David Bardack. Pp. 1-14. January 22, 1965.</span><br />
+    <br />
+    <span style="margin-left: 4em;">2. Chorda tympani branch of the facial nerve in the middle ear of tetrapods.</span><br />
+    <span style="margin-left: 6em;">By Richard C. Fox. Pp. 15-21, May 22, 1965.</span><br />
+    <br />
+    <span style="margin-left: 4em;">3. Fishes of the Kansas River System in relation to zoogeography of the Great</span><br />
+    <span style="margin-left: 6em;">Plains. By Artie L. Metcalf. Pp. 23-189, 4 figures in text, 51 maps.</span><br />
+    <span style="margin-left: 6em;">March 24, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">4. Factors affecting growth and reproduction of channel catfish, Ictalurus punctatus.</span><br />
+    <span style="margin-left: 6em;">By Bill A. Simco and Frank B. Cross. Pp. 191-256, 13 figures in</span><br />
+    <span style="margin-left: 6em;">text. June 6, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">5. A new species of fringe-limbed tree frog, genus Hyla, from Dari&eacute;n, Panam&aacute;.</span><br />
+    <span style="margin-left: 6em;">By William E. Duellman. Pp. 257-262, 1 figure in text. June 17, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">6. Taxonomic notes on some Mexican and Central American hylid frogs. By</span><br />
+    <span style="margin-left: 6em;">William E. Duellman. Pp. 263-279. June 17, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">7. Neotropical hylid frogs, genus Smilisca. By William E. Duellman and</span><br />
+    <span style="margin-left: 6em;">Linda Trueb. Pp. 281-375, pls. 1-12, 17 figures in text.&nbsp; July 14, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">8. Birds from North Borneo. By Max C. Thompson. Pp. 377-433, 1 figure in</span><br />
+    <span style="margin-left: 6em;">text. October 27, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">9. Natural history of cottonmouth moccasin, Agkistrodon piscivorus (Reptilia).</span><br />
+    <span style="margin-left: 6em;">By Ray D. Burkett. Pp. 435-491, 7 figures in text. October 27, 1966.</span><br />
+    <br />
+    <span style="margin-left: 4em;">More numbers will appear in volume 17.</span><br />
+</p>
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of Natural History of Cottonmouth
+Moccasin, Agkistrodon piscovor, by Ray D. Burkett
+
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@@ -0,0 +1,4055 @@
+The Project Gutenberg EBook of Natural History of Cottonmouth Moccasin,
+Agkistrodon piscovorus (Reptilia), by Ray D. Burkett
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Natural History of Cottonmouth Moccasin, Agkistrodon piscovorus (Reptilia)
+
+Author: Ray D. Burkett
+
+Release Date: December 15, 2011 [EBook #38308]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK NATURAL HISTORY OF ***
+
+
+
+
+Produced by Chris Curnow, Joseph Cooper and the Online
+Distributed Proofreading Team at http://www.pgdp.net
+
+
+
+
+
+
+
+Transcriber's Note.
+
+[=X] in Table 12 represents "x bar" or "x overbar" (the mean value).
+
+Hyphenation has been standardised save for the contents of 'Literature
+Cited' and the 'List of Publications.'
+
+
+
+
+  =================================
+
+  UNIVERSITY OF KANSAS PUBLICATIONS
+  MUSEUM OF NATURAL HISTORY
+
+  Vol. 17, No. 9, pp. 435-491, 7 figures in text
+  ------------ October 27, 1966 ----------------
+
+  Natural History of Cottonmouth Moccasin,
+  Agkistrodon piscivorus (Reptilia)
+
+  BY
+
+  RAY D. BURKETT
+
+  UNIVERSITY OF KANSAS
+  LAWRENCE
+  1966
+
+
+
+
+  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
+
+
+  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
+  Frank B. Cross
+
+  Volume 17, No. 9, pp. 435-491, 7 figures in text
+  Published October 27, 1966
+
+  UNIVERSITY OF KANSAS
+  Lawrence, Kansas
+
+  PRINTED BY
+  ROBERT R. (BOB) SANDERS, STATE PRINTER
+  TOPEKA, KANSAS
+  1966
+
+[Illustration: Printer's Logo]
+
+  31-4629
+
+
+
+
+  Natural History of Cottonmouth Moccasin,
+     Agkistrodon piscivorus (Reptilia)
+
+  BY RAY D. BURKETT
+
+
+
+
+CONTENTS
+
+
+                                                                PAGE
+     INTRODUCTION                                                439
+     ACKNOWLEDGMENTS                                             440
+     SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION                   441
+     DESCRIPTION                                                 444
+       Color and Pattern                                         444
+       Scutellation                                              444
+       Dentition                                                 449
+     HABITAT AND LIMITING FACTORS                                450
+     REPRODUCTION                                                452
+       Courtship and Mating                                      452
+       Reproductive Cycles                                       452
+       Embryonic Development                                     454
+       Birth of Young                                            454
+       Number of Young per Litter                                454
+       Population Composition                                    455
+       Reproductive Potential                                    455
+     GROWTH AND DEVELOPMENT                                      456
+       Size at Birth and Early Growth                            456
+       The Umbilical Scar                                        457
+       Later Growth and Bodily Proportions                       457
+     SHEDDING                                                    459
+       The Shedding Operation                                    459
+       Frequency of Shedding                                     460
+     FOOD HABITS                                                 461
+       Methods of Obtaining Prey                                 461
+       Food and Food Preferences                                 462
+     MORTALITY FACTORS                                           465
+       Natural Enemies and Predators                             465
+       Parasites and Diseases                                    465
+       Miscellaneous Causes of Death                             466
+     BEHAVIOR                                                    466
+       Annual and Diel Cycles of Activity                        466
+       Basking                                                   469
+       Coiling                                                   469
+       Locomotion                                                470
+       Disposition                                               470
+       Defense and Escape                                        471
+       "Head Bobbing"                                            471
+       Combat Dance                                              472
+     THE VENOM                                                   473
+       Properties of the Venom                                   473
+       Venom Yield and Toxicity                                  473
+       Susceptibility of Snakes                                  475
+     THE BITE                                                    476
+       Effects of the Bite                                       476
+       Treatment                                                 477
+       Case History of a Bite                                    479
+       Snakebite in the United States                            480
+     SUMMARY                                                     480
+     LITERATURE CITED                                            485
+
+
+
+
+INTRODUCTION
+
+
+Objectives of the study here reported on were to: (1) learn as much as
+possible concerning the natural history and economic importance of the
+cottonmouth; (2) determine what factors limit its geographic
+distribution; (3) determine the role of the cottonmouth in its
+ecological community; and (4) compare the cottonmouth's life history
+with that of other crotalid snakes, especially the kinds that are most
+closely related to it.
+
+Twenty-five live cottonmouths were kept in the laboratory for the
+purpose of studying behavior and fang shedding and for comparison of
+measurements with those of preserved specimens. Live snakes were
+obtained in Brazoria and Nacogdoches counties, Texas, from Hermann Park
+Zoo, Houston, Texas, and from the late Paul Anderson of Independence,
+Missouri. Preserved western cottonmouths were examined for the purpose
+of determining variation, distribution, food habits, body proportions,
+embryonic development, and reproductive cycles. The cottonmouths
+examined include: 221 from Texas; 33 from Arkansas; 22 from Louisiana; 2
+from Illinois; and 1 each from Kansas, Mississippi, and Oklahoma.
+
+In the preparation of this report I have examined all available
+literature pertaining to the cottonmouth and have drawn from these
+sources for comparative or additional material. Some of the more
+noteworthy contributions to knowledge of the cottonmouth are the general
+accounts of the life history by Allen and Swindell (1948), Barbour
+(1956), and Wright and Wright (1957); the publications by Gloyd and
+Conant (1943) concerning taxonomy; Klimstra (1959) concerning food
+habits; and Allen (1937), Parrish and Pollard (1959), Swanson (1946),
+and Wolff and Githens (1939b) concerning the venom. Numerous other
+publications, although brief, contain worthwhile contributions. Also of
+special interest as a source of material for comparison of cottonmouths
+with other crotalids are the works of Fitch (1960) on the copperhead and
+of Klauber (1956) on the rattlesnakes.
+
+The cottonmouth has been well known for nearly 200 years. Wright and
+Wright (1957) listed the following vernacular names that are applied to
+the cottonmouth: black moccasin, black snake, blunt-tail moccasin,
+congo, copperhead, cottonmouth water moccasin, cotton-mouthed snake,
+gapper, highland moccasin, lowland moccasin, mangrove rattler, moccasin,
+North American cottonmouth snake, North American water moccasin, North
+American water viper, pilot, rusty moccasin, salt-water rattler,
+stubtail, stump (-tail) moccasin, stump-tail viper, swamp lion, Texas
+Moccasin, trapjaw, Troost's moccasin, true horn snake, true water
+moccasin, viper, water mokeson, water pilot, water rattlesnake, and
+water viper.
+
+Some of the names listed above are based upon superstition and folklore
+prevailing in pioneer times, and others are based upon the behavior or
+appearance of the snake at various ages. Names like "stump-tail
+moccasin" are derived from the appearance of females which have short
+tails or snakes that have lost part of the tail. Names like "gapper" and
+"trapjaw" came to be applied because of the habit of the snake's lying
+with its mouth open when approached. The name "cottonmouth" also was
+derived from this behavior, although the lining of the mouth is whitish
+in most other snakes. The term "rattlesnake" may have come from the fact
+that the cottonmouth vibrates its tail vigorously when nervous as do
+many other snakes, or it may have been confused with rattlesnakes.
+Because of the general public's fear of snakes and their reluctance to
+learn to discriminate between the poisonous and harmless species,
+numerous kinds of snakes seen in or near water have been called
+moccasins. The general appearance, pugnacious behavior, and whitish
+mouth of water-snakes (_Natrix_) have earned them a bad reputation. In
+fact, a great majority of the "cottonmouths" reported in many areas are
+found to be water-snakes.
+
+The cottonmouth is economically important mainly because of the
+injurious or fatal effects of its bite and the psychological effect that
+its actual or suspected presence has upon many persons. The species eats
+a wide variety of prey items and helps to prevent overabundance of
+certain kinds of organisms. The venom has been used in the therapeutic
+treatment of blood clots owing to its anticoagulant properties
+(Didisheim and Lewis, 1956). It also is employed in the treatment of
+haemorrhagic conditions and rheumatoid arthritis, as well as in the
+production of antivenin (Allen and Swindell, _op cit._:13). None of
+these uses of venom has become widely accepted, and its value is
+questionable.
+
+
+
+
+ACKNOWLEDGMENTS
+
+
+For guidance in the course of my study, I am especially indebted to
+Professor Henry S. Fitch. For suggestions concerning the preparation of
+the manuscript, I thank Professor E. Raymond Hall. I am grateful to my
+wife, Janis, for her invaluable assistance and for typing the
+manuscript.
+
+For use of specimens in their care, I thank Professors William E.
+Duellman, University of Kansas; Robert L. Packard, formerly of Stephen
+F. Austin State College; W. Frank Blair, University of Texas; and
+William B. Davis and Richard J. Baldauf, Texas Agricultural and
+Mechanical College. Mr. John E. Werler of the Hermann Park Zoo, Houston,
+Texas, contributed live individuals; Mr. Richard S. Funk contributed
+information on the birth of a brood of cottonmouths; and Dr. Henry M.
+Parrish contributed information on the incidence of snakebite. To
+numerous other persons at leading museums throughout the United States
+for information on the cottonmouths in their collections, to all who
+helped with the field work in various ways, and to others at the
+University of Kansas for their help and suggestions I am grateful.
+
+
+
+
+SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION
+
+
+Snakes of the genus _Agkistrodon_ are relatively primitive members of
+the Crotalidae, which is one of the most specialized families of snakes.
+A majority of the pit-vipers are found in the Americas, but close
+relatives are found from extreme southeastern Europe through temperate
+Asia to Japan (_A. halys_) and southeastern Asia including Indonesia
+(_Agkistrodon_ and _Trimeresurus_). Familial characters include:
+vertical pupil of the eye; facial pit present between the preoculars and
+loreal; scales usually keeled; short, rotatable maxilla bearing a large
+hollow fang; toothless premaxilla; chiefly hematoxic venom; and
+undivided anal plate.
+
+The genus _Agkistrodon_ includes about nine species in the Old World and
+three in North and Central America. Some of the primitive characters of
+the genus are: head covered with nine enlarged shields or having the
+internasals and prefrontals broken up into small scales; subcaudals on
+proximal part of tail undivided; fangs relatively short; tail lacking
+rattles. In one species, _A. rhodostoma_, the scales are smooth; and the
+female is oviparous and guards her eggs until they hatch. Other species
+have keeled scales and are ovo-viviparous.
+
+There is little paleontological evidence illustrating evolution of the
+cottonmouth or for that matter of crotalids in general. Brattstrom
+(1954) summarized the current knowledge of fossil pit-vipers in North
+America. The few fossils found of the cottonmouth are from Alacha,
+Brevard, Citrus, Levy, Pasco, and Pinellas counties, Florida
+(Brattstrom, _op. cit._:35; Auffenberg, 1963:202). All are of late
+Pleistocene Age and well within the present geographic range of the
+cottonmouth.
+
+Of crotalid genera only _Agkistrodon_ occurs in both the Old World and
+the New World, suggesting that this genus is relatively old. Schmidt
+(1946: 149-150) mentioned several other closely related groups of
+animals found in both eastern Asia and eastern North America, including
+the reptilian genera: _Natrix_, _Opheodrys_, _Elaphe_, _Ophisaurus_,
+_Leiolopisma_ (= _Lygosoma_), _Eumeces_, _Clemmys_, _Emmys_, and
+_Alligator_. Of the groups of animals now confined to these two regions
+the most important are the cryptobranchid salamanders, the genus
+_Alligator_, and the spoon-bills (_Psephurus_ in China and _Polyodon_ in
+the Mississippi drainage). Fossil evidence for these groups indicates
+that existing forms common to eastern Asia and eastern North America are
+remnants of a late Cretaceous or early Tertiary Holarctic fauna which
+was forced southward as the climate became gradually cooler to the
+north. "Other clues suggest that both _Agkistrodon_ and _Trimeresurus_
+(_Bothrops_) moved from Asia to America, one of these presumably giving
+rise to the rattlesnakes." (Darlington, 1957:228).
+
+The named, American kinds of _Agkistrodon_ currently are arranged as
+three species: the copperhead, the cantil and the cottonmouth. The
+copperhead (_A. contortrix_) is divided into four subspecies, all of
+which are terrestrial. This species occurs from southern New England to
+eastern Kansas and along the Atlantic and Gulf Coastal plains, exclusive
+of peninsular Florida and the delta of the Mississippi River in
+Louisiana. It extends southwest from Kansas through the Edwards Plateau
+of west-central Texas. Isolated populations occur in the Chisos and
+Davis mountains of Trans-Pecos Texas. The cantil or Mexican moccasin
+(_A. bilineatus_), probably the nearest relative of the cottonmouth (_A.
+piscivorus_), is divisible into two subspecies and occupies a nearly
+complementary range from Mexico south to Nicaragua. The cottonmouth
+occurs throughout the coastal plains of the southeastern United States,
+usually at altitudes of 500 feet or less. Two subspecies are recognized,
+the eastern _A. p. piscivorus_ and the western _A. p. leucostoma_. A
+revision of the genus is underway by Professor Howard K. Gloyd.
+
+The basic pattern and various behavioral traits are common to all three
+species. The young are more nearly alike in appearance than adults, the
+copperhead and the cottonmouth being easily confused. Adults differ in
+color, size, body proportions, habitat, and habits. In range and habitat
+preference the cottonmouth more closely resembles the southern
+subspecies of the copperhead, _A. c. contortrix_, which is usually found
+in lowlands, near swamps and streams, but seldom in water.
+
+[Illustration: FIG. 1.]
+
+FIG. 1. Geographic range of the cottonmouth, showing marginal and
+near-marginal records, based largely upon maps by Gloyd and Conant
+(1943:165) and Conant (1958:336) but including additional records. The
+more important of these records (from east to west) are discussed in the
+following paragraphs. Crosshatching indicates the area of intergradation
+between the eastern and western subspecies. Old records, indicated by
+dates, and their sources are as follows: 1850's and 1891--U. S. National
+Museum numbers 4263 and 32753 respectively; 1897--Hurter (1897); and
+1895--Stejneger (1895:408).
+
+The northernmost record for the eastern subspecies is in the Petersburg
+area, Prince George County, Virginia (Anon., 1953:24). A sight record
+(Hickman, 1922:39) near Bristol, West Virginia, probably was based on a
+water-snake (_Natrix_ sp.), since the stream in which the snake was seen
+flows north into the Ohio River rather than southeast through Virginia.
+In North Carolina the most inland record is from the Neuse River, six to
+eight miles east of Raleigh (Stejneger, 1895:408). Neill (1947:205)
+reported a population in the vicinity of Dry Fork Creek on the boundary
+line of Wilkes and Oglethorpe counties, Georgia. Distribution of
+cottonmouths in Florida is statewide, including the Keys and other
+offshore islands.
+
+The ranges of the two subspecies, _piscivorus_ and _leucostoma_, meet
+near the eastern border of Mississippi. _A. p. piscivorus_ has been
+reported from Tishomingo County to the Gulf and east of the Loess Bluff
+area in central Mississippi, and _A. p. leucostoma_ has been reported
+from this area westward. A few specimens from along the Coast indicate
+intergradation (Cook, 1962:33) between the two subspecies.
+
+Barbour (1956:33) reported one specimen from Cypress Creek, in the Green
+River drainage, Muhlenberg County, Kentucky, and stated that suitable
+habitat can be found in several areas east of Kentucky Lake. Hence,
+cottonmouths may have entered this area via the Ohio River. Stejneger
+(_loc. cit._) reported the species in the Wabash River at Mount Carmel,
+Wabash County, Illinois, and mentioned a former occurrence at Vincennes,
+Knox County, Indiana; but there are no recent records at these
+localities. Hurter (1897) reported having seen cottonmouths in Illinois,
+opposite St. Louis; Smith (1961:265) believes that this and a population
+in Monroe County, Illinois, are isolated relicts, since no specimens
+have been found within 50 miles to the south of Monroe County. The
+specimens reported by Anderson (1941:178; 1945:274) near Chillicothe
+(three miles southwest and seven miles northwest, respectively),
+Livingston County, Missouri, also are thought to represent a relict
+population. Hall and Smith (1947:453) reported one specimen from Jasper
+County, Missouri, in the Spring River which flows through extreme
+southeastern Kansas and into Oklahoma and another in the Neosho River at
+Chetopa, Kansas. Both of these specimens were taken after a flood, and
+no additional specimens have been taken in this region. Nevertheless,
+sufficient habitat is probably available along the Neosho and Verdigris
+rivers in the southeastern part of Kansas.
+
+In Texas the cottonmouth has penetrated marginal habitat perhaps farther
+than anywhere else in its range. Formerly it was thought to be limited
+to the country east of the Balcones Escarpment (Smith and Buechner,
+1947:8), but semiarid areas of the state have been invaded primarily via
+the Colorado and Brazos River systems up to altitudes of 2300 feet. Two
+additional specimens are said to have been collected along the Rio
+Grande. Dr. Howard K. Gloyd (_in litt._) stated that the specimen
+reported from Eagle Pass, Maverick County, is believed to have been
+taken in the 1850's; and the one said to have come from the mouth of the
+Devil's River is actually marked "near Santa Rosa, Cameron County,
+September 30, 1891." No additional specimens have been taken in that
+area; and the range now probably extends no farther south than Corpus
+Christi, Texas. Brown's (1903:554) knowledge of the extension of the
+range of the cottonmouth west of longitude 98 deg. is probably based upon
+the records along the Rio Grande reported in the nineteenth century.
+
+Three extensions of the known range in Texas are reported herein. One
+specimen was captured by Mr. Harry Green (HWG 346) along the San Saba
+River, 8.1 miles west of Menard, Menard County. The other two specimens
+(KU 84375 and 84376) were taken by the late Paul Anderson one and
+one-half miles north of Pecan Crossing, South Concho River, Tom Green
+County, and one mile west of Mertzon, Irion County.
+
+In the hypsithermal period following Pleistocene glaciation,
+cottonmouths gradually moved northward occupying areas beyond their
+present range. The distributional records since the 1850's and the
+apparent relict populations now in existence indicate that the range
+of this species has since receded.
+
+
+
+
+DESCRIPTION
+
+Color and Pattern
+
+
+Color predominantly brown, ranging through pale reddish-brown or dark
+reddish-brown, brownish-green, to almost black; 10 to 17 irregular dark
+brown bands on paler brown ground color; young paler (some nearly salmon
+pink), retaining a vivid pattern throughout first year; pattern of most
+individuals nearly obliterated by third year; brilliance and dullness of
+predominant color correlated with molting cycle (skin especially bright
+and shiny immediately following shedding); tip of tail yellowish in
+juveniles; posterior part of venter and tail uniformly black in some
+adult individuals, especially females; secondary sexual differences in
+dorsal coloration, such as found in copperhead by Fitch (1960:102), not
+noted.
+
+The eastern subspecies, _A. p. piscivorus_, has the more brilliant
+pattern in which the centers of the dark cross-bands are invaded by the
+ground color. The cross-bands are slightly constricted in the mid-line
+and may or may not be bilaterally symmetrical. One-half of the
+cross-band may be displaced anteriorly or posteriorly to a slight degree
+or may even be completely absent. From one to several dark spots may be
+present within the cross-bands.
+
+The western subspecies, _A. p. leucostoma_, has a comparatively dull
+pattern in which the ground color does not invade the center of the
+cross-bands. In many instances the bands are outlined by white scales,
+as in the Mexican moccasin (this character is not so prominent in _A. p.
+piscivorus_ because of the paler ground color). A large, dark blotch
+usually occurs at the base of the cross-band and may completely cross
+the ventral scales. The characteristic variations found in _piscivorus_
+are also present in _leucostoma_.
+
+The number of bands is often difficult to count because of the dark
+color of some specimens. Gloyd and Conant (1943:168) reported averages
+of 12.5 (11 to 16) and 12.2 (10 to 16) in males and females,
+respectively, of _leucostoma_ and ranges of 10 to 17 for males and 10 to
+16 for females with averages of 13 in both sexes of _piscivorus_. On 20
+specimens of _leucostoma_ from Texas the average number of bands was
+12.7 (11 to 15). If the number of bands differed on the two sides of an
+animal, the total number of the two sides was divided by two.
+
+
+Scutellation
+
+The scutellation of the cottonmouth closely resembles that of the other
+species of _Agkistrodon_. For example, the nine cephalic shields are
+characteristic of most species of _Agkistrodon_, as well as most other
+primitive crotalids and viperids, and most colubrids. Most individuals
+have an additional pair of large scales behind the parietals.
+
+The numbers of postoculars, supralabials, and infralabials are variable.
+On either side the postoculars (three in most specimens) are reduced to
+two in some specimens. The supralabials (eight in most specimens)
+frequently vary (usually on one side only) from seven to nine. The
+number of infralabials is somewhat more variable than the number of
+supralabials, the usual number being 11, but 10 is also common; 8, 9,
+and 12 are more rare (Table 1). In 102 snakes in which these characters
+were examined, four different combinations of supralabials and seven
+combinations of infralabials were found. Both characters together
+yielded 16 combinations, considering only the actual number of scales
+and not taking into account the side of the head on which they occurred
+(Table 2). The combinations found in a brood of seven young from
+Houston, Texas, are shown in Table 3 to illustrate the variability of
+this character. Gloyd and Conant (1943:168) found a variation of 6 to 11
+(8) and 7 to 9 (8) supralabials and 8 to 13 (11) and 8 to 12 (10.4)
+infralabials in samples of 301 _leucostoma_ and 119 _piscivorus_,
+respectively (numbers in parentheses represent average). Also of
+interest is the variability of the scales themselves. In one instance a
+scale was found that had not completely divided. In another specimen the
+last supralabial and last infralabial were one scale that completely
+lined the angle of the jaw. Instances of one scale almost crowding out
+another were common. In still other instances one or two supralabials
+were divided horizontally into two scales. Individual variation rather
+than geographical variation occurs in these characters.
+
+     TABLE 1.--Frequency of Occurrence of Various Numbers of
+     Supralabial and Infralabial Scales in 102 Cottonmouths.
+
+      ====================================================
+     |          |Specimens  |Specimens |      |           |
+     |Number    |having     |having    |Total |Percentage |
+     |of scales |number on  |number on |      |           |
+     |          |both sides |one side  |      |           |
+     |----------------------------------------------------|
+     |                     Supralabials                   |
+     |----------------------------------------------------|
+     |    7     |    11     |    24    |  35   |   25.2   |
+     |    8     |    64     |    27    |  91   |   65.5   |
+     |    9     |     0     |    3     |   3   |    2.2   |
+     |----------------------------------------------------|
+     |                      Infralabials                  |
+     |----------------------------------------------------|
+     |    8     |     0     |    2     |   2   |    1.5   |
+     |    9     |     3     |    10    |  13   |    9.6   |
+     |    10    |    12     |    32    |  44   |   32.4   |
+     |    11    |    53     |    22    |  75   |   55.1   |
+     |    12    |     0     |    2     |   2   |    1.5   |
+      ----------------------------------------------------
+
+     TABLE 2.--Numbers of Supralabials and Infralabials of 102
+     Cottonmouths.
+
+      ===========================================
+     |  Number of  |  Number of   |  Number of   |
+     | individuals | supralabials | infralabials |
+     |     37      |      8       |      11      |
+     |     15      |      8       |    10-11     |
+     |     12      |     7-8      |      11      |
+     |      6      |     7-8      |    10-11     |
+     |      5      |      8       |      10      |
+     |      5      |      8       |     9-10     |
+     |      4      |      7       |      11      |
+     |      3      |      7       |     9-10     |
+     |      3      |     7-8      |      10      |
+     |      2      |      7       |      9       |
+     |      2      |      7       |      10      |
+     |      2      |      8       |    10-12     |
+     |      2      |     8-9      |      10      |
+     |      2      |     7-8      |     8-9      |
+     |      1      |     7-8      |      9       |
+     |      1      |     8-9      |    10-11     |
+      -------------------------------------------
+
+The dorsal scales of cottonmouths are strongly keeled except that those
+of the two lower scale-rows on each side are weakly keeled. Also they
+are slightly larger than the others. Two apical pits are present on each
+dorsal scale. The shape of the scales and number of scale rows vary
+depending upon the position on the body. Scales on the neck are
+considerably smaller than those elsewhere on the body and are arranged
+in two or three more rows than those at mid-body. The skin in the region
+of the throat, neck, and fore-body is especially elastic and allows the
+swallowing of large prey. Posteriorly from the mid-body the scales
+decrease in size and become more angular, those on the tail tending to
+be rhomboidal and wider than long. In the region of the anus the number
+of scale rows diminishes rapidly, leaving only 12 to 14 rows at the base
+of the tail and only three rows immediately ahead of the tail tip. The
+tail ends in a spine composed of two scales: one scale covers the
+bottom, lower parts of the sides, and tip of the spine; and a shorter
+dorsal scale covers the top and upper parts of the sides of the basal
+two-thirds of the spine. The spine of embryos and young cottonmouths is
+blunt, but is pointed in most adults.
+
+     TABLE 3.--Variation in Numbers of Supralabials and Infralabials
+     in a Brood of Seven Cottonmouths.
+
+     ===========================================
+    |  Number of  |  Number of   |  Number of   |
+    | individuals | supralabials | infralabials |
+    |      1      |      7       |      9       |
+    |      1      |      7       |     9-10     |
+    |      2      |     7-8      |     8-9      |
+    |      1      |     7-8      |      9       |
+    |      1      |      8       |     9-10     |
+    |      1      |     8-9      |      10      |
+     -------------------------------------------
+
+     TABLE 4.--Analysis of Number of Scale Rows at Three Parts of
+     the Body in 81 Cottonmouths.
+
+   ==============================================================
+  |        |       Neck      |     Mid-body    | Anterior to anus|
+  |        |--------+--------+--------+--------+--------+--------|
+  | Number | Number |  Per-  | Number |  Per-  | Number |  Per-  |
+  |   of   |   of   |centage |   of   |centage |   of   |centage |
+  | scales |indivi- |        |indivi- |        |indivi- |        |
+  |per row | duals  |        | duals  |        | duals  |        |
+  |--------+--------+--------+--------+--------+--------+--------|
+  |   29   |    1   |   1.2  |  ...   |  ...   |  ...   |  ...   |
+  |   28   |    3   |   3.7  |  ...   |  ...   |  ...   |  ...   |
+  |   27   |   52   |  64.2  |  ...   |  ...   |  ...   |  ...   |
+  |   26   |   16   |  18.0  |    2   |   2.5  |  ...   |  ...   |
+  |   25   |    8   |   9.9  |   67   |  82.7  |  ...   |  ...   |
+  |   24   |    1   |   1.2  |    4   |   4.9  |  ...   |  ...   |
+  |   23   |  ...   |  ...   |    8   |   9.9  |    4   |   4.9  |
+  |   22   |  ...   |  ...   |  ...   |  ...   |    4   |   4.9  |
+  |   21   |  ...   |  ...   |  ...   |  ...   |   68   |  84.0  |
+  |   20   |  ...   |  ...   |  ...   |  ...   |    5   |   6.2  |
+   --------------------------------------------------------------
+
+The number of scale rows on the neck, at mid-body, and just anterior to
+the anus is relatively constant at 27-25-21, respectively; but some
+individual variation is evident (Table 4). Since the rows are diagonally
+arranged, it is necessary in counting scales to proceed either
+anteriorly or posteriorly across the back; or the row may be counted in
+either direction up to the center of the back and then reversed on the
+other side of the snake. In order to count the scale rows in a position
+where no scale reduction or addition was occurring and to avoid as much
+error as possible, I counted from anterior to center and back on the
+neck, in any direction at mid-body, and from posterior to center and
+back near the anus. Because females generally are the larger in
+circumference posteriorly, they could have more scale rows than males
+just anterior to the anus. The few snakes having more than 21 scale rows
+in the posterior region offer no conclusive evidence as to tendencies,
+but in both instances in which this occurred the females outnumbered the
+males three to one. An odd, rather than an even, number of scale rows
+occurs on most of the length of the snakes examined, because there is a
+mid-dorsal row and scale rows tend to be lost on both sides at about the
+same level. An example of scale reduction of one snake was as follows:
+
+      6+7 (13)                  6+7 (96)
+   27 --------  25 --------  24 --------   23 ---------  22 ---------
+      5+6 (13)     5+6 (90)                   7+8 (111)     7+8 (114)
+
+                                6+7 (122)                  +7, -5 (125)
+   23 --------  22 --------  23 ---------  21 --------  22 ------------
+      -6 (118)     +6 (119)     6+7 (121)     +6 (123)
+
+      -6 (126)
+   22 --------  21 (130).
+
+This scale reduction follows the method proposed by Dowling (1951b: 133)
+in which the numbers on the mid-line represent the number of scale rows,
+upper figures refer to the right side of the snake, and figures in
+parentheses indicate the number of the ventral scale (counted from the
+anterior end of the series), thus marking the position of the addition
+or reduction. Addition of a row is shown by a plus sign and the number
+of the row, whereas reductions are shown by a minus sign and the number
+of the row that is lost or by a plus sign between the number of two rows
+that join. According to Dowling, variation in number of dorsal scales
+characterizes the few genera and species of snakes in which it has been
+studied. The time and difficulty involved in ascertaining the number of
+scales explain why it has not been widely used in classification.
+
+[Illustration: FIG. 2. Number of ventral scales in 48 female and 34
+male _A. p. leucostoma_.]
+
+Ventral scales on 34 males averaged 134.4 (128 to 139), and on 48
+females 133.5 (128 to 137) (Fig. 2.). Barbour (1956:34) found an average
+of 135.3 ventral scales on 64 males and 44 females, and Gloyd and Conant
+(_loc. cit._) found an average of 134 for both males and females. The
+average for the eastern cottonmouth obtained by Gloyd and Conant,
+however, was 137 ventrals in both sexes. Some of my counts were made
+before I knew of the standard system of counting ventrals proposed by
+Dowling (1951a:97-99), in which the first ventral plate is defined as
+the most anterior one bordered on both sides by the first row of
+dorsals. Therefore, some inconsistencies may exist in my counts. Where
+differences occur, Dowling's method probably will indicate the presence
+of an additional scale, since it appears to begin farther anteriorly on
+the average, than I began counting.
+
+[Illustration: FIG. 3. Number of caudal scales in 44 female and 34
+male _A. p. leucostoma_.]
+
+     TABLE 5.--Caudal Scale Combinations in 95 Cottonmouths.
+     U = Undivided; D = Divided.
+
+   =====================================================================
+          |                         Number of scales
+          |-------------------------------------------------------------
+   Number |   |     |     |   |    |   |    |   |     | |  | |  | | | |
+   of     |   |     |     |   |    |   |    |   |     | |  | |  | | | |
+   samples| D |  U  |  D  | U | D  | U |  D | U |  D  |U| D|U| D|U|D|U|D
+   -------+---+-----+-----+---+----+---+----+---+-----+-+--+-+--+-+-+-+-
+     25   |   |13-35|10-32|   |    |   |    |   |     | |  | |  | | | |
+     11   |1-2|12-33|14-28|   |    |   |    |   |     | |  | |  | | | |
+     20   |   |16-39| 1-9 |1-3|3-24|   |    |   |     | |  | |  | | | |
+     20   |1-4| 3-37| 1-21|1-5|1-29|   |    |   |     | |  | |  | | | |
+      4   |   |14-30| 1-8 |1-7|1-8 |1-4|2-10|   |     | |  | |  | | | |
+      3   | 1 |18-23| 1-2 |1-2|6-11|1-3|6-9 |   |     | |  | |  | | | |
+      4   |   | 1-17|   1 |1-3|1-8 |1-4|1-3 |1-4|13-22| |  | |  | | | |
+      2   |1-2| 4-16|   1 |1-4| 2  | 1 |1-4 | 1 |18-21| |  | |  | | | |
+      1   |   |  20 |   1 | 1 | 1  | 1 | 6  | 1 |  3  |1|11| |  | | | |
+      1   |   |  10 |   2 | 3 | 2  |10 | 1  | 2 |  2  |1| 4|4|  | | | |
+      1   |   |  20 |   1 | 1 | 2  | 1 | 1  | 4 |  4  |2| 4|1| 3| | | |
+      1   | 1 |  13 |   1 | 1 | 1  | 3 | 1  | 1 |  1  |4| 2|4|13| | | |
+      1   |   |  17 |   1 | 1 | 2  | 1 | 1  | 6 |  2  |1| 2|3| 2|7| | |
+      1   |   |   9 |   1 | 1 | 8  | 1 | 3  | 1 |  1  |3| 1|1| 2|1|1|1|6
+   ---------------------------------------------------------------------
+
+Analysis of caudal scales revealed sexual dimorphism. In the six
+specimens from Tennessee, Blanchard (1922:16) found the same thing.
+Caudals averaged 45.4 (41 to 50) on 34 males and 42.6 (39 to 49) on 44
+females (Fig. 3). Barbour (_loc. cit._) found an average of 45.7 (30 to
+54) caudals in males and 43 (17 to 56) in females. Caudal scale counts
+by Gloyd and Conant (_loc. cit._) averaged 44 (38 to 49) in males and 42
+(37 to 48) in females of _leucostoma_; in _piscivorus_ they averaged 48
+(42 to 53) in males and 44 (41 to 49) in females. Another
+seldom-mentioned, unusual characteristic of the caudal scales of
+copperheads and cottonmouths is that some are single (usually those at
+the base of the tail) and others divided (Table 5). To my knowledge, all
+other species have either single or divided scales the entire length of
+the tail. See Klauber (1941:73) and Fox (1948:252) concerning
+correlation of few scales with warm environment.
+
+
+Dentition
+
+Cottonmouths, like other pit-vipers, have their teeth reduced in number
+and have enlarged, highly specialized fangs. Small teeth occur on the
+palatine and the pterygoid in the upper jaw and on the dentary in the
+lower jaw. The dentary bone bears 17 curved teeth that decrease in size
+posteriorly. The palatine bears five small, strongly curved teeth, and
+the pterygoid bears 16 to 18 strongly curved teeth decreasing in size
+posteriorly. The numbers of teeth mentioned above in each instance refer
+to the number of sockets rather than the actual number of teeth, because
+teeth are frequently shed, leaving some of the sockets empty at any one
+time.
+
+The maxillary bone has two sockets side by side which bear the poison
+fangs, usually one at a time. During the period shortly before a fang is
+to be shed, however, its replacement becomes attached in the alternate
+socket; and both fangs may be functional for a short time. The old fang
+then becomes weakened at its base, eventually breaks off, and is
+swallowed. At any one time four or five replacement fangs in various
+stages of development are found in the gum behind the functional fang.
+These replacement fangs, which are arranged in alternate rows, gradually
+enlarge as they move forward in their development and, in juveniles, are
+generally slightly longer than the fangs that they replace.
+
+In 1963 I examined the fangs of 14 cottonmouths at four- to seven-day
+intervals for a period of six weeks. The fang-shedding cycle was found
+to be highly irregular, with a double condition (on one or both sides)
+occurring one-third of the time. Approximately the same proportion of
+double fangs was found in preserved individuals. A replacement period of
+at least five days was observed in one snake. One-half the cycle (from
+replacement on one side to replacement on the other) varied from five to
+twenty days, indicating that the cycles for each fang are independent of
+one another. Bogert (1943:324) found that young rattlesnakes are born
+with functional fangs in the two inner sockets. Nonsynchronous use of
+the sockets on opposite sides of the head in rattlesnakes is a later
+development which results from accidents or other conditions leading to
+a longer retention of the fang on one side than on the other (Klauber,
+1956:723). I found a double set of fangs in cottonmouths only twice in
+the six-week period. A complete cycle was recorded in ten instances in a
+period of 19 to 23 days and in two instances in 32 days. One cottonmouth
+was examined periodically over a 34-day period by Allen and Swindell
+(1948:12), but a complete fang-shedding cycle was not observed. Fitch
+(1960:110) reported a 33-day cycle in copperheads; Klauber (1956:726)
+estimated the normal active life of each fang of an adult rattlesnake to
+be from six to ten weeks, but he made no observations to confirm his
+estimation.
+
+Fangs measured from the tip of the notch of the basal lumen to the end
+of the fang vary from about 1.3 per cent of the snout-vent length in
+juveniles to about 1.0 per cent in large adults (Table 6). The fangs are
+longer than those of copperheads (Fitch, 1960:111). Klauber's (1956:736)
+figures on fang-lengths in all species of rattlesnakes are percentages
+of total length rather than of the snout-vent length. The fangs of
+various species of rattlesnakes range from nearly the same proportionate
+length as those of cottonmouths to some much longer.
+
+From patterns of bites of venomous snakes, Pope and Perkins
+(1944:333-335) attempted to correlate number, size, and patterns of
+tooth marks with size and generic identity of the snake responsible for
+the bite. Distance between fangs is relatively constant for snakes of a
+particular size (Table 6) regardless of genus, but the fangs of a
+cottonmouth are directed outward to variable degrees, and puncture
+wounds could easily resemble those of a much larger snake (Table 7).
+Also there is no direct relationship between size of snake and toxicity
+or amount of venom injected. Consequently information of this kind is of
+little or no value from a medical standpoint.
+
+     TABLE 6.--Correlation of Relative Fang-length and Distance
+     Between Fangs at Base with Snout-vent Length of Cottonmouths.
+
+   =======================================================
+  |Snout-vent    |Number |Average     |Number |Average    |
+  |length        |in     |ratio of    |in     |ratio of   |
+  |(millimeters) |sample |fang-length |sample |distance   |
+  |              |       |to          |       |between    |
+  |              |       |snout-vent  |       |fangs to   |
+  |              |       |length      |       |snout-vent |
+  |              |       |(percent)   |       |length     |
+  |              |       |            |       |(percent)  |
+  |--------------+-------+------------+-------+-----------|
+  |   200-299    |   3   |    1.33    |   3   |   2.57    |
+  |   300-399    |   7   |    1.30    |   5   |   2.48    |
+  |   400-499    |  13   |    1.21    |   9   |   2.21    |
+  |   500-599    |  12   |    1.22    |   8   |   2.19    |
+  |   600-699    |   7   |    1.17    |   1   |   2.10    |
+  |   700-799    |   5   |    1.07    |   4   |   1.65    |
+  |   800-899    |   1   |    1.00    |   1   |   2.00    |
+   -------------------------------------------------------
+
+     TABLE 7.--Contrast in Measurements Between the Base of the
+     Fangs and Between Fang Punctures of Nine Cottonmouths (in
+     millimeters).
+
+   ==================================================
+  | Distance between | Distance between | Snout-vent |
+  |  base of fangs   |  fang punctures  |   length   |
+  |------------------+------------------+------------|
+  |       7.7        |       13.0       |    400     |
+  |       8.7        |       14.0       |    575     |
+  |      10.0        |       22.5       |    526     |
+  |      11.0        |    18.0-19.0     |    590     |
+  |      12.0        |       18.0       |    793     |
+  |      13.0        |    17.0, 20.0    |  558, 612  |
+  |      15.5        |       23.5       |    800     |
+  |      16.0        |       24.0       |    800     |
+   --------------------------------------------------
+
+
+
+
+HABITAT AND LIMITING FACTORS
+
+
+Although usually associated with swamps and lowlands along river
+bottoms, the cottonmouth lives in a variety of habitats ranging from
+salt marshes to cool, clear streams and from sea level to an altitude of
+2300 feet. Shaded, moist areas either in or beside shallow waters are
+preferred, but cottonmouths occasionally wander as far as a mile from
+water.
+
+In the pine-oak forests of Nacogdoches County in eastern Texas
+cottonmouths and copperheads are probably the most abundant species of
+snakes. Specimens have been collected near Nacogdoches in ponds, swamps,
+clear and fast-running streams with rock bottoms, and sluggish muddy
+streams. On the Stephen F. Austin Experimental Forest numerous
+cottonmouths live in a swamp until around mid-July, when it becomes dry.
+A small stream west of the swamp seems to be used as a migration route
+to and from the swamp. Slightly more than a mile downstream cottonmouths
+are common in a bottomland area. The ground is always moist and no
+undergrowth occurs; a few small clear springs produce shallow trickles
+that run into a swamp. Cottonmouths can often be found here, lying in or
+beside the small trickles.
+
+I have seen cottonmouths in various types of aquatic habitats in
+Brazoria County. In most places in this area, cottonmouths are found in
+association with one or more species of water-snakes (including _Natrix
+cyclopion_, _N. erythrogaster_, _N. rhombifera_, and _N. confluens_),
+which greatly outnumber the cottonmouth. Interspecific competition may
+be reduced somewhat by cottonmouths sometimes feeding on water-snakes.
+
+The numerous statements in the literature concerning the habitat of the
+cottonmouth can be summarized most easily by the following short
+quotations:
+
+     _Agkistrodon piscivorus piscivorus_--"Marshes and lakes; ponds
+     and streams with wooded shores; low country near water;
+     roadside ponds; drainage ditches; coastal 'banks'; keys; some
+     Gulf coast islands; mangrove swamps." (Wright and Wright,
+     1957:919.)
+
+     _Agkistrodon piscivorus leucostoma_--"Cypress, gum, river
+     swamps; alluvial swamps wooded or not wooded; water courses of
+     the south such as rivers, bayous, backwaters of small branches;
+     hill streams in the north; ... marshy places in prairies ...
+     rice fields, bottomland pools; margins of above habitats,
+     pools, shallow lakes, swampy places, temporary flood lands....
+     In, under, or on fallen timber, in holes in banks, rocky
+     bluffs, crayfish burrows. In short it is very aquatic." (Wright
+     and Wright, _op. cit._:923.)
+
+Geographically cottonmouths differ somewhat in their ecological
+requirements, but are basically much alike in most respects. The areas
+of greatest abundance are those having 40 inches or more of annual
+rainfall. The northern edge of the range has a mean temperature of
+approximately 38 deg. F. in January in Virginia and 30 deg. F. in Missouri,
+although the lowest temperature reached in these areas is more important
+as a limiting factor. The annual rainfall in both Virginia and Missouri
+amounts to approximately 40 inches. Moisture, as well as temperature,
+may play an important role in the northward distribution of the species.
+The eastern cottonmouth seems to be less tolerant of low temperatures
+than the western subspecies. Mean January temperatures equal to those
+along the northern limits of the western cottonmouth's distribution are
+reached in the vicinity of Connecticut, which is north of the geographic
+range of the eastern subspecies.
+
+The depths to which cottonmouths penetrate into their dens may have a
+limiting influence upon the geographic range, especially in the northern
+extremes. Bailey (1948:215) discussed the possibility that populations
+of snakes may be significantly depressed because of winter kill of
+individuals that "hibernate" at shallow depths. He speculated also that
+the short growing season does not allow enough time for the essentials
+of existence to be carried out, and the prolonged period of inactivity
+overtaxes the energy reserve of the species.
+
+Available food does not seem to be of much importance as a limiting
+factor, for the cottonmouth is remarkably indiscriminate in its choice
+of prey, feeding upon almost any vertebrate animal that happens to come
+within reach. Competition for food, however, may play an important role.
+
+
+
+
+REPRODUCTION
+
+Courtship and Mating
+
+
+A review of available literature indicates no records of courtship of
+the cottonmouth other than statements that breeding occurs in early
+spring. In a close relative, the copperhead (see Fitch, 1960:159-160),
+mating occurs almost any time in the season of activity but is mainly
+concentrated in the few weeks after spring emergence, at about the time
+when females are ovulating. Klauber (1956:692) concluded that along the
+southern border of the United States rattlesnakes normally mate in
+spring soon after coming out of their winter retreats; but farther north
+where broods are produced biennially, the mating times may be more
+widely dispersed, and summer and fall matings may even predominate.
+
+The only record of copulation in the cottonmouth was reported by Allen
+and Swindell (1948:11), who observed a pair copulating for three hours
+on October 19, 1946, at the Ross Allen Reptile Institute. Davis
+(1936:267-268) stated that courtship in cottonmouths is violent and
+prolonged but did not note any nervous, jerky motions or nudging of the
+female along her back and sides as had been observed in other genera of
+snakes. Carr (1936:90) saw a male cottonmouth seize a female in his
+mouth and hold her, but no courtship followed.
+
+
+Reproductive Cycles
+
+Many persons have assumed that gestation periods in snakes are the
+intervals between mating and parturition, and that mating and ovulation
+occur at approximately the same time. However, retention of spermatozoa
+and delayed fertilization indicate that copulation is not a stimulus for
+ovulation.
+
+A biennial reproductive cycle was found for the copperhead in Kansas
+(Fitch, 1960:162), the prairie rattler in Wyoming (Rahn, 1942:239) and
+in South Dakota (Klauber, 1956:688), the great basin rattler in Utah
+(Glissmeyer, 1951:24), and the western diamondback rattler in
+northwestern Texas (Tinkle, 1962:309). Klauber's (1956:687) belief that
+the reproductive cycle of rattlesnakes varies with climate, being
+biennial in the north and annual in the south, is supported by similar
+climatic variation in the reproductive cycle of the European viper which
+was discussed by Volsoe (1944:18, 149).
+
+If data for a large number of females were arranged as are those in
+Table 8, they might reveal whether the breeding cycle is annual or
+biennial. The figures presented in Table 8 are misleading if viewed
+separately because of the small number of individuals included in some
+of the size classes.
+
+The smallest reproductive female found measured 455 millimeters in
+snout-vent length. Conant (1933:43) reported that a female raised in
+captivity gave birth to two young at an age of two years and ten months.
+The size classes represented by gravid females found by Barbour
+(1956:38) in Kentucky indicate that breeding occurs at least by the
+third year.
+
+The ovaries of female cottonmouths examined revealed ova in various
+stages of development. In individuals less than 300 millimeters in
+snout-vent length the ovaries are almost completely undeveloped; in
+immature individuals from 300 to 450 millimeters in length the follicles
+are from one to two millimeters in length; in post-post females
+follicles vary in size, the largest being about seven millimeters.
+Reproductive females also contain follicles of various sizes. One or two
+sets are less than three millimeters in length, and large ova that soon
+are to be ovulated are present. Ovarian ova found in April ranged in
+length from 23 to 35 millimeters. No embryonic development was observed
+in most individuals until June or later.
+
+     TABLE 8.--Percentage of Gravid Females of _A. p. leucostoma_ in
+     50 Millimeter Size Classes.
+
+   =====================================
+  |Snout-vent |Number |Total |Percentage|
+  |           |  of   |number|          |
+  |  length   |gravid |  in  |  gravid  |
+  |           |females| size |          |
+  |           |       |class |          |
+  |-----------+-------+------+----------|
+  | 450-499   |   3   |  14  |   21.4   |
+  | 500-549   |   7   |  17  |   41.2   |
+  | 550-599   |   8   |  17  |   47.1   |
+  | 600-649   |   5   |  7   |   71.4   |
+  | 650-699   |   2   |  9   |   22.2   |
+  | 700-749   |   2   |  3   |   66.7   |
+  | 750-799   |   1   |  1   |  100.0   |
+  | 850-899   |   1   |  1   |  100.0   |
+  |  Totals   |  29   |  69  |   42.0   |
+   -------------------------------------
+
+Increase in length of testes appears to be correlated with length of the
+individual rather than cyclic reproductive periods (Fig. 4).
+
+The reproductive cycle in cottonmouths resembles that illustrated by
+Rahn (_op. cit._:237), in which the ovarian follicles of post-partum
+females begin to enlarge in late summer and autumn, with ovulation
+occurring the following spring. By means of retaining sperm successive
+broods possibly are produced after only one mating. In captivity, at
+least, some females may not follow this biennial cycle; Stanley Roth
+(M.S.), biology teacher in high school at Lawrence, Kansas, had a female
+of _A. p. piscivorus_, from Florida, that produced broods of 14 and 12
+young in two consecutive years.
+
+[Illustration: FIG. 4. Length of testes in cottonmouths of various
+sizes (.--left; º--right). The right testis is always longer than
+the left.]
+
+
+Embryonic Development
+
+After ova are fertilized a three and one-half to four-month period of
+development begins which varies somewhat depending on the temperature.
+In almost every instance the ova in the right uterus outnumber those in
+the left. Embryos usually assume the serpentine form in the latter part
+of June and are coiled in a counterclockwise spiral with the head on the
+outside of the coil. At this time the head is relatively large and
+birdlike in appearance with conspicuous protruding eyes. Sex is easily
+noted because the hemipenes of males are everted. By late July scales
+are well developed and the embryo is more snakelike in appearance, but
+pigmentation is still absent. By mid-August the color and pattern are
+well developed, the egg tooth is present, the snake shows a considerable
+increase in size over that of the previous month, and much of the yolk
+has been consumed. Some females that contain well developed embryos also
+contain eggs that fail to develop. Sizes of ova vary irrespective of
+size of female and stage of embryonic development. Lengths of ova ranged
+from 22 to 51 millimeters in May to 35 to 49 millimeters in July and
+August. A two-yolked egg was found in one female.
+
+
+Birth of Young
+
+Accounts in the literature of 15 litters of cottonmouths fix the time of
+birth as August and September. Conant (1933:43) reported the birth of a
+litter in mid-July by a female that had been raised in captivity, and
+one female that I had kept in captivity for two months gave birth to a
+litter between October 19 and October 25. The conditions of captivity
+undoubtedly affected the time of birth in both instances.
+
+Wharton (1960:125-126) reported the birth and behavior of a brood of
+seven cottonmouths in Florida. I was given notes of a similar nature by
+Richard S. Funk of Junction City, Kansas, on a brood of five
+cottonmouths. The mother of the brood was caught in June, 1962, in
+Tarrant County, Texas, by Richard E. Smith, and was 705 millimeters in
+snout-vent length. The first young was found dead in an extended
+position a few inches from the fetal membranes at 11:05 p.m. on August
+22. The second young was born at 11:07 p.m. The intervals between the
+successive births were three, seven, and four minutes; and time until
+the sac was ruptured in each instance was six, five, eight, and 11
+minutes. The time interval between the rupture of the sac and emergence
+of each individual was 41, 92, 154, and 34 minutes. The mother's actions
+in giving birth to the last four young were essentially as described by
+Wharton (_loc. cit._), except that the intervals between successive
+births did not increase. Within one minute after rupturing the sac and
+while its head was protruding, each of the four living young opened its
+mouth widely from three to seven times, then took its first breath.
+Breaths for the first three hours were steady at three or four per
+minute but then decreased to two or three per minute. Pulse rate for the
+four averaged 38 per minute while at rest but increased to 44 per minute
+after voluntarily crawling.
+
+
+Number of Young per Litter
+
+Records of from one to 16 young per litter have been reported (Ditmars,
+1945:330; Clark, 1949:259), but the average is probably between six or
+seven. Most accounts in the literature present information on number of
+ova or embryos per female rather than the number of young. Size and age
+of the mother (Table 9) influence the number of ova produced. Allen and
+Swindell (1948:11) recorded three to 12 embryos in 31 cottonmouths
+varying in total length from 26 to 44 inches. An average of 6.5 embryos
+per female was found.
+
+     TABLE 9.--Number of Ova Produced by Fecund Cottonmouths.
+
+  ====================+============+======================
+    Snout-vent length |  Number    |    Number of ova,
+     in millimeters   | in sample  | average and extremes
+  --------------------+------------+----------------------
+         450-549      |     10     |     4.1 (2 to 7)
+         550-649      |     11     |     4.9 (1 to 8)
+         650-749      |      4     |     6.3 (4 to 8)
+         750-849      |      1     |          5
+         850-949      |      1     |         14
+  --------------------------------------------------------
+
+Mortality at birth has been recorded for almost every litter born in
+captivity (see Allen and Swindell, _loc. cit._; Conant, 1933:43;
+Wharton, 1960:125). A female that I kept in captivity gave birth to
+seven young. Three never ruptured their sacs, and another died soon
+after leaving the sac. The effects of captivity on females may result in
+higher rates of deformity and mortality in young than is common in
+nature. Klauber (1956:699-700) estimated that the defects brought about
+by conditions of captivity on rattlesnakes eliminate about three young
+per litter.
+
+
+Population Composition
+
+No investigator has yet analyzed the composition of a population of
+cottonmouths according to age, sex and snout-vent length. Barbour
+(1956:35) did sort 167 snakes into size classes, but did not determine
+sex ratio, size at sexual maturity, reproductive cycles, or snout-vent
+length. He recorded total lengths from which snout-vent lengths cannot
+be computed because of differential growth rates and different bodily
+proportions of the two sexes. I judge from my findings that he included
+immature individuals in his three smallest size classes (45.5 per cent
+of the population). I found at least 32.5 per cent immature individuals
+(Fig. 5) in my material, but it was not a natural population.
+
+The sex ratios of several small collections from natural populations
+varied, and no conclusions could be drawn. Females comprised 53 per cent
+of the specimens included in Fig. 5 and in a group of 48 embryos which
+represented eight broods. That percentage may not be the percentage in a
+natural population but is used in making assumptions because I lack
+better information.
+
+
+Reproductive Potential
+
+If data in Fig. 5 are representative of a natural population and if 61
+per cent of the females are sexually mature, the reproductive potential
+can be estimated as follows: assuming a cohort of 1000 cottonmouths
+contains 530 females, 61 per cent of the females (323 individuals)
+probably are adults. If 42 per cent of these females produce 6.5 young
+per female in any season (Tables 8 and 9), 136 females will produce 884
+young. But if 50 per cent of the adult females are reproductive (as
+would be assumed if reproduction is biennial), 1050 young will be
+produced. Actually the number of young required per year to sustain a
+population is unknown, because mortality rates at any age are unknown.
+
+[Illustration: FIG. 5. Composition of a group of cottonmouths examined
+in this study. Individuals less than 450 millimeters in snout-vent
+length are considered as immature. Specimens from 200 to 249 millimeters
+in length are included in the 200-millimeter class, _etc._]
+
+
+
+
+GROWTH AND DEVELOPMENT
+
+Size at Birth and Early Growth
+
+
+Size at birth depends on the health of the mother. According to Fitch
+(1960:182), many litters of copperheads born in captivity are stunted.
+Seven young cottonmouths (two males and five females) born in captivity
+were each 185 millimeters in snout-vent length and 40 millimeters in
+tail length. Weights of the three living young were 10.0, 10.1, and 11.1
+grams. Another litter of five young measured by Richard S. Funk were
+larger, and differences in the proportions of the tail length and
+snout-vent length suggest the sexual dimorphism found in larger
+individuals. However, sex of these young snakes was not recorded.
+Snout-vent length and tail length in millimeters were 232, 41; 243, 47;
+229, 40; 240, 48; and 225, 40 in the order of their birth. These snakes
+are considerably smaller than the nine young of _A. p. piscivorus_
+reported by Wharton (1960:127) that averaged 338 millimeters total
+length and 28.7 grams. The yolk of one young _piscivorus_ was 11.7 per
+cent of the total weight. Yolk is used up in about two weeks if its rate
+of utilization resembles that of the copperhead as reported by Gloyd
+(1934:600).
+
+Early rates of growth of three living young are shown in Table 10. On
+the 56th day after birth, each was fed one minnow less than two inches
+long. Between the 80th and 120th days three additional small minnows
+were fed to each snake. Young cottonmouths increase nearly 50
+millimeters in length by the first spring if they inhabit warm areas and
+feed in autumn or winter.
+
+Variation in size of newborn cottonmouths may be less in nature than in
+captivity. Average size at birth can be determined accurately by the
+size of young captured in early spring, at least in northern parts of
+the range where winter feeding and growth do not occur at all or are
+negligible. Total lengths of 19 juveniles thought by Barbour (1956:38)
+to be seven to eight months old do not differ markedly from lengths of
+the five newly-born young measured by Funk.
+
+     TABLE 10.--Rate of Growth of Three Young Cottonmouths.
+
+      ========+=================================================
+     |        |  Snout-vent length/tail length--weight in grams  |
+     |  Age   +----------------+----------------+----------------|
+     |in days |  Female No. 1  |  Female No. 2  |      Male      |
+     |--------+----------------+----------------+----------------|
+     |    2   | 185/40--11.1   | 185/40--10.1   |  185/40--10.0  |
+     |    7   | 192/40--       | 190/40--       |  189/40--      |
+     |   22   | 195/40--10.3   | 200/41.5--10.6 |  197/40--      |
+     |   80   | 204/40--11.7   | 203/42--10.4   |  218/48--14.3  |
+     |   88   |      ....      | 204/44--       |      ....      |
+     |  143   | 215/40.5--13.3 |      ....      |  225/48--15.1  |
+      --------+----------------+----------------+----------------
+
+
+The Umbilical Scar
+
+The umbilical cord is broken at birth and the navel closes within a few
+days; but the scar, involving from two to four ventral scales, remains
+throughout life. Position of the scar was found by Edgren (1951:1) to be
+sexually dimorphic in the eastern hog-nose snake (_Heterodon
+platyrhinos_), but nothing has been published on this matter concerning
+the cottonmouth. Consequently, I counted the scales of several
+individuals from the anal plate, and there was no marked difference in
+the position of the scar in males and females; it varied in position
+from the 10th to the 18th scale. When counted from the anterior end, the
+scar ranged from ventral number 115 to 122 (average, 119) in 28 females
+and from number 117 to 126 (average, 121) in 14 males. The difference
+between male and female cottonmouths is not nearly so great as in
+_Heterodon_.
+
+
+Later Growth and Bodily Proportions
+
+The only records of growth increments in a natural population of
+cottonmouths are those in Table 11. The period of growth is mostly the
+period of activity, and differences are expected between northern and
+southern populations. As size increases, determination of growth rate
+becomes more difficult because age classes overlap in size. Growth of
+any individual depends not only on climate and food but also on disease
+and parasitism and the innate size potential. Stabler (1951:91) showed
+weight and length relationships in two cottonmouths for a period of six
+and one-half years.
+
+     TABLE 11.--Growth Increments in Cottonmouths (Barbour,
+     1956:38-39).
+
+   =============================================
+  | Number of |   Total   |Estimated| Estimated |
+  |           |  length   |   age   |  growth   |
+  |           |           |         |   from    |
+  |           |           |         | preceding |
+  |           |           |         |   year    |
+  |individuals|    in     |in months|    in     |
+  |           |millimeters|         |millimeters|
+  |-----------+-----------+---------+-----------|
+  |    19     |  260-298  |   7-8   |    25     |
+  |    11     |  312-337  |  19-20  |    45     |
+  |    40     |  355-485  |  31-32  |    95+-    |
+  |    83     |  500-1000 |  43-44+ |     ?     |
+   ---------------------------------------------
+
+My study failed to reveal any secondary sexual difference in growth rate
+and maximum size. Of the 306 cottonmouths measured by me, 16 males and
+five females exceeded 700 millimeters in snout-vent length. Two males
+were more than 850 millimeters long. One cottonmouth lived in captivity
+for 18 years and 11 months (Perkins, 1955:262). The maximum total
+lengths were reported by Conant (1958:186-187) to be 74 inches (1876
+mm.) in _A. p. piscivorus_ and 54 inches (1370 mm.) in _A. p.
+leucostoma_.
+
+[Illustration: FIG. 6. Head length (º) and head width (.) expressed as a
+percentage of snout-vent length of living and preserved cottonmouths.
+Head length was measured from the tip of the snout to the posterior end
+of the mandible. Head width was measured across the supraocular scales,
+since accuracy was greater than if measured at the posterior edge of the
+jaw. No sexual dimorphism or geographical variation occurs in these
+characters.]
+
+Proportions of various parts of the body vary considerably depending on
+age, size and, in some instances, sex. Heads are proportionately larger
+in young than in adults (Fig. 6), as is true of vertebrates in general.
+This larger head has survival value for the cottonmouth in permitting
+more venom to be produced and in permitting it to be injected deeper
+than would be the case if the proportions were the same as in adults.
+Relative to the remainder of the snake the head is considerably larger
+than in the copperhead (Fitch, 1960:108) and slightly larger than in the
+rattlesnake, _Crotalus ruber_ (Klauber, 1956:152).
+
+[Illustration: FIG. 7. Tail length expressed as a percentage of
+snout-vent length of living and preserved cottonmouths (.--males;
+º--females).]
+
+In general, tails are relatively longer in males than in females of the
+same size (Fig. 7), except that there is little or no difference at
+birth. Growth of the tail in males proceeds at a more rapid rate. In
+certain individuals sex cannot be recognized from length of the tail
+relative to snout-vent length because overlapping occurs, especially in
+medium-sized individuals. Similar changes of proportions with increase
+in age occur in copperheads (Fitch, 1960:106) and rattlesnakes (Klauber,
+1956:158-159), but the tail of the cottonmouth is relatively much
+longer.
+
+
+
+
+SHEDDING
+
+The Shedding Operation
+
+
+Shedding of the skin is necessary to provide for growth and wear in
+snakes. The milkiness or bluing of the eyes, which causes partial
+blindness, marks the initial stage of shedding and is caused by a
+discharge of the exuvial glands that loosens the old _stratum corneum_
+from the layer below. In four to seven days the opaqueness disappears,
+and the snake sheds after an additional three to six days (Table 12).
+Young snakes first shed within a few days after birth and generally shed
+more frequently than adults, but the interval is variable. The eyes of
+three young cottonmouths observed by Wharton (1960:126) became milky on
+the fourth day but cleared on the seventh day, and the skin was shed on
+the eighth day. The eyes of three young kept by me became milky two to
+three days after birth, cleared on the seventh to tenth days, and the
+skin was shed on the thirteenth day. Possibly the relatively long
+interval in this instance resulted from low relative humidity in the
+room where the snakes were kept. According to Fitch (1960:134), litters
+of young copperheads usually shed within three to ten days after birth;
+but under unusually dry conditions shedding did not occur for several
+weeks.
+
+     TABLE 12.--Duration of Preparatory Period (in days) to Shedding
+     in 11 Cottonmouths.
+
+   ==============================
+  |Duration  |  Time  |Time from |
+  |   of     |between |beginning |
+  |cloudiness|clearing|    of    |
+  |          |  and   |cloudiness|
+  |of eyes   |shedding|  until   |
+  |          |        | shedding |
+  |----------+--------+----------|
+  |    5     |   6    |    11    |
+  |    7     |   3    |    10    |
+  |    -     |   -    |     6    |
+  |    -     |   -    |     6    |
+  |    5     |   3    |     8    |
+  |    4     |   6    |    10    |
+  |    7     |   3    |    10    |
+  |    5     |   6    |    11    |
+  |    5     |   3    |     8    |
+  |    7     |   -    |    -     |
+  |    7     |   3    |    10    |
+  |   ----   |    ----|     ---- |
+  |[=X] 5.4  |[=X] 3.8| [=X] 9.0 |
+   ------------------------------
+
+Cottonmouths as well as other snakes usually do not feed until after the
+skin is shed and are generally quiescent during the period preceding
+shedding, except that immediately before shedding they become active and
+rub their snouts on some rough object and may yawn several times
+seemingly in an attempt to loosen the skin along the edges of the lips.
+After the skin is loosened from the head, more rubbing against rough
+surfaces and writhing serves to pull the old skin off, turning it inside
+out. Once the old skin has passed over the thick mid-body, the snake
+often crawls forward using rectilinear locomotion until the skin is
+completely shed. It normally comes off in one piece; but, if the snake
+is unhealthy or has not had sufficient food or water, the skin may come
+off in patches. Frequently one or both of the lens coverings are not
+shed immediately and impair the sight. Bathing or swimming ordinarily
+causes dried skin to peel off; and, because of the cottonmouth's aquatic
+habits, its chances of shedding successfully are much greater than those
+of less aquatic snakes. Cottonmouths that have recently shed have bright
+and glossy patterns, in contrast to the dull and dark appearance of
+those that are preparing to shed.
+
+
+Frequency of Shedding
+
+Most of our knowledge concerning the frequency of shedding is based upon
+observations of captives. It is known that the intervals between
+exuviations are largely dependent upon the amount of food taken and the
+rate of growth. Unless laboratory conditions closely resemble those in
+the field, shedding frequencies in captives probably differ much from
+those of free-living snakes.
+
+Only two of my captives shed twice. The intervals between exuviations in
+the two snakes were eight and five months, lasting from August to April
+and from December to May, respectively. Ten other snakes shed once in
+the period from January through July. Stabler (1951:91) presented data
+concerning shedding of two cottonmouths kept 12 and 14 years in
+captivity. One shed 25 times in 12 years and the other shed 37 times in
+14 years, giving an average of 2.1 and 2.6 per year, respectively.
+Neither of the snakes shed from December through March, but the period
+of shedding corresponded to the period of greatest activity and growth.
+In Florida, cottonmouths shed four to six times a year, according to
+rate of growth (Allen and Swindell, 1948:7).
+
+
+
+
+FOOD HABITS
+
+Methods of Obtaining Prey
+
+
+Food is obtained by a variety of methods depending on the type of food,
+age of the cottonmouth, and possibly other factors. Some captives lie in
+ambush and others crawl slowly in active search. At the first cue of
+possible prey, either by sight, scent, or differential temperature
+detection by the pit, the snake appears to become alert and flicks its
+tongue out at fairly rapid intervals.
+
+By means of the facial or loreal pit found in all crotalids, the snake
+is able to detect objects having temperatures different from that of the
+surroundings of the objects. In detecting prey the tongue acts to
+sharpen the sense of "smell" by conveying particles to Jacobson's organs
+in the roof of the mouth. On many occasions cottonmouths appeared to
+rely solely on sight; they passed within a few inches of prey,
+apparently unaware of its presence until it moved. When pools of water
+begin to dry up toward the end of summer, cottonmouths often congregate
+and feed on dying fish. In these instances the fish are usually taken as
+they come to the surface. In laboratory observations moccasins seize
+live fish and some moccasins carry the fish until they have received
+lethal doses of venom; afterward the fish are swallowed. But grasping
+and manipulation of the prey occurs without the fangs' being employed,
+especially in the case of dead fish. On one occasion a cottonmouth was
+observed to grasp the edge of a glass dish that had contained fish and
+apparently retained the odor. On another occasion I placed several fish
+in a bowl, rubbed a stick on the fish, and then touched each snake
+lightly on the nose with the stick. The snakes crawled directly to the
+bowl and began feeding. At other times these same snakes crawled around
+the cage in an apparent attempt to locate the food but paid little
+attention to fish held in front of them. If the catching of prey under
+natural conditions were as uncoordinated as it sometimes is in
+captivity, the snakes probably would not be able to survive.
+
+Wharton (1960:127-129) described tail-luring in one individual of a
+76-day-old brood of cottonmouths. The snake lay loosely coiled with the
+tail held about six centimeters from the ground; a constant waving
+motion passed posteriorly through the terminal inch of the tail. These
+movements ceased at 7:20 p.m. but were resumed at 7:40 a.m. the
+following day. All observations were under artificial light. The "caudal
+lure" as a means of obtaining prey has been described in other species
+and related genera by Neill (1960:194) and Ditmars (1915:424).
+
+Various authors have suggested that the method of capture differs
+according to the kind of prey. Allen and Swindell (1948:5) stated that
+cottonmouths retain their hold after striking fish or frogs but will
+release a mouse after delivering a bite and are timid in striking at
+larger rodents. Neill (1947:203) noted that a cottonmouth always waited
+several minutes after biting a large rat before approaching its prey.
+This same type of behavior has been reported for copperheads (Fitch,
+1960:194) and rattlesnakes (Klauber, 1956:618). Cottonmouths observed by
+me retained a strong hold on fish, frogs, and sometimes mice, but almost
+always released large mice and baby chicks, which were not eaten until
+after death.
+
+Different behavior according to type of prey is correlated with ability
+of prey to retaliate, although some animals may not be released because
+they could easily escape. For instance, a frog could hop far enough to
+escape in a matter of seconds if released. A 73-millimeter _Rana
+pipiens_ that I observed was bitten twice within one and a quarter hours
+and died 45 minutes after the last bite. Its movement was uncoordinated
+by the time of the second bite, but it could have escaped had the frog
+not been confined. Although it is doubtful that normal, healthy fish are
+frequently captured by cottonmouths, Allen (1932:17) reported that a
+cottonmouth was seen pushing a small, dead pike about on the surface of
+a stream. A wound on the belly of the fish indicated that it had been
+bitten. A 17-gram creek chub (_Semotilus_) and a 13.7-gram bass
+(_Micropterus_) were injected by me with one-fourth cubic centimeter of
+fresh venom near the base of the tail in order to determine whether the
+fish could escape after being bitten and released. The creek chub
+flipped onto its back after a minute and 45 seconds and gill movements
+stopped in eight minutes and 35 seconds; the bass flipped over after 50
+seconds and died in two minutes and 10 seconds. The venom immediately
+affected both fish, and it is unlikely that either could have swum more
+than a few feet.
+
+After its prey has been killed, a cottonmouth examines the body from end
+to end by touching it with the tongue. Then the animal is grasped in the
+mouth without the use of the fangs and is slowly manipulated until one
+end (usually the head) is held in the mouth. The lengthy process of
+swallowing then takes place, the fangs and lower jaws alternately
+pushing the prey down the throat.
+
+
+Food and Food Preferences
+
+The cottonmouth seems to be an opportunistic omni-carnivore, because it
+eats almost any type of flesh that is available, including carrion. It
+feeds primarily upon vertebrates found in or near water; but
+invertebrates and eggs have also been found in the diet. The only
+potential prey items that seem not to be normally eaten are bufonid
+toads and tadpoles. I have occasionally offered tadpoles and frogs to
+cottonmouths, but only the frogs were accepted. But, Stanley Roth kept a
+cottonmouth in captivity that ate both toads and tadpoles. If tadpoles
+are commonly eaten, their probable rapid digestion would make
+identification almost impossible.
+
+Following is a list of known foods of the cottonmouth:
+
+     Captivity: "... rattlesnake.... The same moccasin also killed
+     and ate a smaller snake of its own species...." (Conant,
+     1934:382.)
+
+     Florida: "3 heron feathers, bird bone, _Eumeces inexpectatus_,
+     3 fish all under one inch in length, 1 heron egg shell" (Carr,
+     1936:89). According to Allen and Swindell (1948:5), "the food
+     included other moccasins, prairie rattlesnakes, king-snakes,
+     black snakes, water snakes, garter snakes, ribbon snakes, and
+     horn snakes ... most of the species of frogs, baby alligators,
+     mice, rats, guinea pigs, young rabbits, birds, bats, squirrels,
+     and lizards ... a mud turtle ... a case of a four footer eating
+     ten to twelve chicken eggs. The most common food appears to be
+     fish and frogs. Catfish are included on this list...." Yerger
+     (1953:115) mentions "an adult yellow bullhead, _Ameiurus
+     natalis_ ... 306 mm. in standard length [from a 63-inch
+     cottonmouth]."
+
+     Georgia: "... full grown _Rana catesbeiana_, several foot-long
+     pickerel ... dead fish if placed in a pan of water.... _Natrix
+     sipedon fasciata_ and _Masticophis flagellum_ ... rats....
+     Toads and large _Eumeces laticeps_ were always ignored."
+     (Neill, 1947:203.) "_Natrix_, _Heterodon_, _Kinosternon_,
+     _Rana_, _Hyla cinerea_, _Microhyla_, Microtine [_Pitymys
+     pinetorum_]." (Hamilton and Pollack, 1955:3.)
+
+     Mississippi: "... _Hyla gratiosa_.... In captivity specimens
+     have eaten frogs, mice, birds, dead fish, pigmy rattlers and
+     copperheads. Toads ... were refused" (Allen, 1932:17). One
+     moccasin "disgorged a smaller decapitated moccasin ... killed
+     the day before by boys" (Smith and List, 1955:123).
+
+     Tennessee: "Beetles in one stomach; lizard (_Eumeces_) in
+     another stomach; small snake (_Natrix_) in one intestine, and
+     hair in another intestine. One stomach contained numerous bits
+     of wood, up to four inches in length...." (Goodman, 1958:149.)
+
+     Kentucky: "_Siren intermedia_ was the most abundant food item
+     in both volume and occurrence. Frogs of the genus _Rana_ ranked
+     second. Together, these two items comprised almost 2/3 of the
+     food of the snakes. The other food items were distributed among
+     the fishes, reptiles, and other amphibians [one _Rana_ tadpole
+     included]." (Based on 42 samples--Barbour, 1956:37.)
+
+     Illinois: (Based on 84 samples--Klimstra, 1959:5.)
+
+                          _Per cent Frequency_    _Per cent_
+     _Food Item_            _of Occurrence_        _Volume_
+
+     Pisces                      39.3                31.9
+     Amphibia                    36.9                26.0
+     Reptilia                    25.0                18.2
+     Mammalia                    30.9                17.9
+     Gastropoda                  17.8                 1.0
+     Miscellaneous               25.0                 5.0
+       (Algae, Arachnida,
+       Aves, Insecta)
+
+     Louisiana: Penn (1943:59) mentions that a "female had just
+     eaten two young cottonmouths...." Clark (1949:259) mentions
+     "100 specimens--34 fish; 25 _Rana pipiens_; 16 _Rana
+     clamitans_; 7 _Acris_; 4 _Natrix sipedon confluens_; 8 birds; 5
+     squirrels ... catfish thirteen and one-half inches in length
+     ... small-mouth black bass [eleven inches]."
+
+     Oklahoma: Force (1930:37) remarks that the moccasin "eats
+     bullfrogs ... but refuses leopard frogs." Trowbridge (1937:299)
+     writes: "several sun perch.... Another had eaten six catfish
+     six to ten inches long ... a water snake (_Natrix s.
+     transversa_) about 18 inches long ... frogs, mostly _Rana
+     sphenocephala_." Carpenter (1958:115) mentions "a juvenile
+     woodthrush.... Seven last instar cicadas ... a young
+     cottontail." According to Laughlin (1959:84), one moccasin
+     "contained the following items: 18 contour feathers of a duck,
+     probably a teal; one juvenile cooter turtle, _Pseudemys
+     floridana_; and a large mass of odd-looking unidentifiable
+     material. The other cottonmouth contained one juvenile pond
+     turtle, _Pseudemys scripta_...."
+
+     Texas: "... several ... feeding on frogs.... One ... found DOR
+     was found to contain a large catfish." (Guidry, 1953:54.)
+
+Of 246 cottonmouths that I examined for food items, only 46 contained
+prey in their digestive tracts. Almost all of the snakes examined were
+museum specimens that had been collected at many places over a period of
+about 40 years. It was not known how long each had been kept alive
+before being preserved. Therefore it was impossible to determine what
+proportion of any population of cottonmouths could be expected to
+contain food. The food items were not analyzed numerically because the
+scales and hair, by means of which many food items in the intestine were
+identified, yielded no clue as to the number of individuals actually
+present unless several distinct kinds were found. Each occurrence of
+scales or hair was thus recorded as a single individual, although some
+such occurrences may have represented more than one animal. The contents
+of some stomachs were so well digested that it was difficult to
+determine the number of items present. As a rule only one food item was
+present in a digestive tract, but a few tracts contained several items
+of the same or different species. Three frogs (_Acris crepitans_) were
+in one snake and three hylas (_Hyla versicolor_) in another. Still
+another individual captured beside a drying pond contained six
+individuals of _Lepomis_ each about three inches long and two pikes
+(_Esox_) about six inches long.
+
+    TABLE 13.--Analysis of Food Items of 46 Cottonmouths Collected
+    in Arkansas, Louisiana, and Texas (1922-1962).
+
+   ===========================+========+==========+=========+==========
+  |                           | Number | Percent  |Estimated|Estimated |
+  |                           |   of   |          |         |          |
+  |                           |samples |frequency | weight  |percentage|
+  |                           |   in   |          |         |          |
+  |        FOOD ITEMS         | which  |    of    |   in    |    by    |
+  |                           |  item  |          |         |          |
+  |                           |occurred|occurrence|  grams  |   bulk   |
+  |---------------------------+--------+----------+---------+----------|
+  |Fish                       |  (7)   |   13.2   |   20    |   18.4   |
+  |  _Esox_ sp.               |   1    |          |         |          |
+  |  _Lepomis_ sp.            |   2    |          |   15    |          |
+  |  Unidentified             |   4    |          |         |          |
+  |Amphibians                 |  (12)  |   23.0   |         |   20.4   |
+  |  _Scaphiopus hurteri_     |   1    |          |   13    |          |
+  |  _Acris crepitans_        |   2    |          |    4    |          |
+  |  _Hyla cinerea_           |   2    |          |   12    |          |
+  |  _Hyla versicolor_        |   1    |          |   12    |          |
+  |  _Rana catesbeiana_       |   1    |          |   20    |          |
+  |  _Rana pipiens_           |   3    |          |   15    |          |
+  |  Unidentified             |   2    |          |         |          |
+  |Reptiles                   |  (15)  |   28.4   |         |   29.9   |
+  |  _Pseudemys scripta_      |   2    |          |   15    |          |
+  |  _Anolis carolinensis_    |   1    |          |    6    |          |
+  |  _Eumeces fasciatus_      |   1    |          |    7    |          |
+  |  _Lygosoma laterale_      |   2    |          |    5    |          |
+  |  _Natrix_ sp.             |   1    |          |   10    |          |
+  |  _Natrix erythrogaster_   |   2    |          |   10    |          |
+  |  _Agkistrodon piscivorus_ |   2    |          |   20    |          |
+  |  _Crotalus_ sp.           |   1    |          |   30    |          |
+  |  Unidentified snakes      |   3    |          |         |          |
+  |Birds                      |  (4)   |   7.6    |         |   18.6   |
+  |  _Anhinga anhinga_ (juv.) |   1    |          |   60    |          |
+  |  Egret (head and neck)    |   1    |          |   20    |          |
+  |  Passeriformes            |   2    |          |   20    |          |
+  |Mammals                    |  (6)   |   11.3   |         |   12.7   |
+  |  _Blarina brevicauda_     |   1    |          |   12    |          |
+  |  Cricetinae               |   5    |          |   18    |          |
+  |Unidentified               |  (9)   |   17.0   |         |          |
+   ---------------------------+--------+----------+---------+-----------
+
+The "unidentified" category (Table 13) refers to jellylike masses in the
+stomach or material in the intestine in which no scales, feathers, hair,
+or bones could be found. Most of the unidentifiable matter could be
+assumed to consist of remains of amphibians, since they leave no hard
+parts. If this assumption is correct, amphibians comprise about 40 per
+cent of the diet. Since intestinal contents were included, a volumetric
+analysis was not feasible. Therefore, the weight of each type of food
+item was estimated and the percentage by bulk calculated from it (Table
+13).
+
+Pieces of dead leaves and small sticks constituted most of the plant
+material found and presumably were ingested secondarily because they
+adhered to the moist skin of the prey, especially to fish and
+amphibians. However, some plant materials probably are eaten because
+they have acquired the odor of the prey. One cottonmouth contained a
+_Hyla cinerea_, several leaves, and five sticks from 37 to 95
+millimeters long and from 12 to 14 millimeters in diameter.
+
+Most reports in the literature state that gravid females do not feed,
+but four gravid females examined by me containing large, well-developed
+embryos also contained evidences of having recently fed. Two of them had
+scales of snakes in the stomach or intestine, one contained a six-inch
+_Lepomis_, and the other had hair in the intestine and the head and neck
+of an adult egret in the stomach.
+
+
+
+
+MORTALITY FACTORS
+
+Natural Enemies and Predators
+
+
+Published records of other animals preying on cottonmouths or killing
+them are few. Reptiles more often than other classes of vertebrates prey
+on the cottonmouth. McIlhenny (1935:44) reported on the scarcity of
+snakes in areas where alligators were present. Predation on cottonmouths
+by indigo snakes (_Drymarchon corais_) was reported by Conant (1958:153)
+and Lee (1964:32). Allen and Swindell (1948:6) obtained a photograph of
+a king-snake (_Lampropeltis getulus_) killing a cottonmouth but thought
+that moccasins are not eaten by _L. getulus_. However, one occasion
+reported herein shows that cottonmouths are eaten by king-snakes; and
+Clark (1949:252) reported finding 13 cottonmouths, along with other
+prey, in the stomach contents of 301 king-snakes (_L. g. holbrooki_)
+from northwestern Louisiana. Cannibalism is also common among
+cottonmouths. Klauber (1956:1058;1079) cited predation on cottonmouths
+by a blue heron (_Ardea herodias_) and a largemouth bass (_Micropterus
+salmoides_). Man is probably the greatest enemy of the cottonmouth.
+Intentional killing, capturing, road kills, and alteration of the
+environment destroy large numbers.
+
+
+Parasites and Diseases
+
+Allen and Swindell (1948:12) listed several diseases and parasites of
+snakes and stated that "some moccasins captured in the woods are so poor
+and weak from parasitic infection that they can barely crawl." The only
+kind of ectoparasite found on captive cottonmouths in the course of my
+study was a snake mite, _Ophionyssus natricus_. An infestation of that
+mite was thought to be partly responsible for the death of one captive
+moccasin. Other moccasins spent increasing amounts of time in their
+water dish after they became infected with mites. Under natural
+conditions frequent swimming probably keeps cottonmouths nearly free of
+mites.
+
+Endoparasites found included lung flukes, stomach nematodes, and
+tapeworms. Lung flukes (_Ochetosoma_ sp.) were found in 16 of 20 captive
+cottonmouths. Snails and frogs serve as intermediate hosts for various
+stages in the life cycle of these flukes. The high percentage of
+cottonmouths infested with flukes is indicative of the use of frogs as a
+major source of food. Less than ten flukes were usually observed in the
+snakes' mouths but occasionally more were seen. One snake was observed
+thrashing about in its cage for nearly an hour, after which time it
+died. Upon examination of the mouth, 32 flukes were found, most of which
+were located in the Jacobson's organs. Whether or not flukes caused the
+death is not known. Nematodes (_Kalicephalus_ sp.) were found in the
+stomach of each of several preserved specimens; most of these snakes had
+no food in their digestive tracts. In a high percentage of the
+moccasins, tapeworms (_Ophiotaenia_ sp.) were in the duodenum, in many
+instances so tightly packed as seemingly to prevent passage of food. The
+importance of fish in the diet is reflected by the high percentage of
+snakes containing tapeworms. An unidentified cyst (?) about an inch long
+and containing two hooks on one end was found attached to the outer wall
+of the stomach of a cottonmouth. Yamaguti (1958) listed all the kinds of
+helminths known from cottonmouths.
+
+
+Miscellaneous Causes of Death
+
+Munro (1949:71-72) reported on the lethal effect of 10 per cent DDT
+powder on two young cottonmouths which were dusted with it to kill
+mites. Herald (1949:117) reported an equal effect caused by spraying a
+five per cent DDT solution in a room with several snakes. All but three
+large cottonmouths, which were under shelter at the time of spraying,
+were killed.
+
+One individual that refused to eat was dissected soon after death, and a
+short piece of a branch on which two large thorns were located at 90 deg.
+angles was found blocking the intestine at the posterior end of the
+stomach.
+
+An unexpected and probably unusual circumstance caused the death of two
+captives. After cleaning a cage containing five cottonmouths and placing
+several mice in the cage for food, I noticed two of the snakes lying
+stretched out, partially on one side, and almost unable to move. At
+first I thought they had been bitten by other snakes which were in
+pursuit of the mice. The two died after two days. When a similar
+incident occurred in another cage, I removed the "bitten" snake and it
+fully recovered after 11 days. When the same symptoms were observed in a
+garter snake in another cage, I realized that in each instance the cage
+had been cleaned and fresh cedar chips placed in it immediately prior to
+observation of these symptoms. Fine cedar dust on the chips had
+evidently poisoned the snakes.
+
+
+
+
+BEHAVIOR
+
+Annual and Diel Cycles of Activity
+
+
+In the days following emergence in spring, cottonmouths often endure
+uncomfortable and even dangerous temperatures in order to obtain food
+and mates. They are more sluggish at this time and more vulnerable to
+predation than later in the season when temperatures are optimal. Fitch
+(1956:463) found that copperheads in northeastern Kansas begin their
+annual cycle of activity in the latter part of April, when the daily
+maximum temperature is about 22 deg. C. and the minimum is about 4 deg. C., and
+become dormant in late October or early November, at which time the
+daily maximum temperature is about 15 deg. and the minimum is about 0 deg..
+Indications are that in the northern part of its range the annual
+activity cycle of the cottonmouth resembles that of the copperhead in
+northeastern Kansas. Klimstra (1959:2) captured cottonmouths from April
+to October in southern Illinois. Barbour (1956:36) collected large
+numbers of them in early April in Kentucky and stated that they migrate
+from swamps to wooded hillsides in late August and early September.
+Spring migrations begin after a few consecutive warm days in March. In
+northern Oklahoma cottonmouths have been found along the Verdigris River
+as early as March, suggesting that a few winter in crayfish holes and
+mammal burrows. The majority of individuals found in this area were at
+denning sites along cliffs above the river and emerged later than those
+near the river (Dundee and Burger, 1948:1-2). In Virginia cottonmouths
+have been seen as early as March 5 (Martin and Wood, 1955:237) and as
+late as December 4. They have been observed in migration from the swamps
+of the barrier beach to the mainland in late October and early November
+in southeastern Virginia (Wood, 1954a:159). According to Neill
+(1947:204), the cottonmouth tolerates lower temperatures than do most
+snakes in Georgia and is one of the last to go into hibernation. Allen
+and Swindell (1948:4) stated that cottonmouths usually bask during the
+mornings of the cooler months in Florida, but they mentioned nothing of
+denning such as occurs farther north. Although winter aggregations occur
+in the northern parts of the range, I have never seen such aggregations
+in the South. However, in one instance related to me by a reliable
+observer, seven cottonmouths were found together on a creek bank near
+the Gulf Coast in early spring.
+
+During late summer and early autumn, fat is deposited in lobes in the
+lower abdomen in preparation for the period of winter quiescence. Gravid
+females usually do not feed so frequently or so much as other snakes,
+because they tend to become inactive as the ova develop. Whether or not
+females feed heavily after parturition and previous to denning is not
+known. Peaks of activity in autumn may be caused by final attempts to
+feed before denning and by the appearance of large numbers of newborn
+young. The young usually have from one to two months in which to feed
+before the advent of cold weather. According to Barbour's (_op.
+cit._:38) findings, the young probably feed before hibernation because
+they grow substantially in winter. For those that do not feed, the rate
+of survival is perhaps much lower.
+
+In preparation for winter, cottonmouths migrate inland, usually to dry
+forested hillsides where they den, commonly among rocks at the tops of
+bluffs, along with several other species of snakes. In such aggregations
+there is no hostility and each individual may derive benefit from
+contact with others by which favorable conditions of temperature and
+humidity are maintained.
+
+Neill (1947:204) has found many specimens in winter by tearing bark from
+rotting pine stumps on hillsides overlooking lakes or streams. On cold
+days they evidently retreat below the surface, while on warm days they
+lie just below the bark or emerge and bask. Neill believes that the use
+of stumps by cottonmouths is an innate pattern of behavior, because of
+the large number of young-of-the-year found in such surroundings.
+Cottonmouths were observed in winter also under logs and stumps by Allen
+(1932:17). I have twice observed cottonmouths crawling into crayfish
+burrows along the Gulf Coast of Texas, and suppose they are used as
+denning sites to some extent.
+
+The diel cycle of activity of cottonmouths is of necessity closely
+related to the seasonal cycle. Since optimal temperatures determine
+activity, the diel cycle varies greatly from time to time. It has been
+well established that cottonmouths, like most other crotalids and many
+snakes of other families, prefer nocturnal to diurnal activity, even
+though the temperature may be less favorable at night. This preference
+is correlated with increased nocturnal activity of frogs and reptiles
+that constitute the principal food supply.
+
+During spring and autumn, activity is more restricted to the day and
+long periods of basking occur. However, as hot weather approaches,
+basking occurs mainly in the morning and evening and activity becomes
+primarily nocturnal. But, in well shaded, moist forests, cottonmouths
+feed actively in the daytime.
+
+Availability of food also has an important influence upon activity.
+Allen and Swindell (_op. cit._:5) stated that moccasins congregate
+around drying ponds and feed on dying fish until the moccasins can hold
+no more. They then usually stay nearby as long as food remains. In an
+area of the Stephen F. Austin Experimental Forest near Nacogdoches,
+Texas, many cottonmouths journey daily to and from a swamp and a dry
+field, evidently to feed on rodents inhabiting the area. Ten individuals
+captured along a snake-proof fence that was built 30 yards from the
+swamp were found lying coiled along the fence after 4:30 p.m., at which
+time the area was shaded. On another occasion, I captured a large
+cottonmouth that was feeding upon dying fish in a drying pool about
+10:30 a.m. on August 19, 1962.
+
+Because of the aquatic habits of the cottonmouth, relative humidity
+probably has little influence on the snake's activity. However,
+cottonmouths are more restricted to the vicinity of water in dry weather
+than during rains or muggy weather when many of their natural prey
+species also move about more freely. Increased activity on cloudy days
+may result from protection from long exposure to sunshine. Torrential
+rains and floods, such as those following hurricanes along the Gulf and
+Atlantic coasts of the southeastern United States, bring out quantities
+of snakes of all species. Rattlesnakes and cottonmouths in particular
+are killed by the thousands at these times because they seek shelter in
+human habitations. However, these are unusual circumstances and do not
+reflect voluntary activity as a result of preferences.
+
+Thermal reactions of reptiles were classified by Cowles and Bogert
+(1944) into several categories. For each species there is a basking and
+normal activity range limited by the voluntary minimum and voluntary
+maximum at which the animal seeks shelter. Beyond this normal range are
+the critical thermal minimum and critical thermal maximum (C. T. M.) at
+which effective locomotion is prevented. The lethal minimum and maximum
+are those temperatures at which short exposure produces irreparable
+damage, and death inevitably results. These classifications are modified
+somewhat by seasonal or laboratory acclimation or by the physiological
+state of the animal. The C. T. M. of five cottonmouths was determined by
+placing each individual in an enclosed area and heating it with an
+infrared lamp. Cloacal temperatures were taken with a Schultheis
+quick-recording thermometer as soon as the snake could no longer right
+itself when placed on its back. All temperatures were in degrees
+Celcius. The C. T. M. averaged 39.2 deg. (38.0 deg. to 40.0 deg.). A temperature of
+38.0 deg. was lethal to one individual. These cottonmouths had been in
+captivity for nine months. The behavior of the snakes during heating
+resembled those instances described by Klauber (1956:382-387) for
+rattlesnakes. As the body temperature of the snakes rose past the
+optimum, each individual became disturbed and tried to escape from the
+enclosure. The snakes soon became frantic in their efforts to escape.
+After about five minutes the mouth was opened and heavy, slow breathing
+was begun, accompanied by a loss of coordination and a slowing down of
+movements. The snakes writhed spasmodically for a few seconds and then
+lay still, usually with the mouth open. Recovery was begun by rolling on
+the belly and flicking the tongue, followed by movements of the head and
+then the body. Cottonmouths are rarely exposed to dangerously high
+temperatures owing to their semi-aquatic habits, but there are probably
+occasions when individuals reach the C. T. M. for the species.
+
+
+Basking
+
+Since activity, digestion, and gestation depend upon adequate internal
+temperatures, there must be a process by which these temperatures are
+attained and for an appropriate time maintained. Basking is important in
+this respect. The cottonmouths prefer to lie in a coiled position and,
+during basking, can usually be found beside bodies of water or on
+branches of dead trees overhanging the water. They are good climbers and
+have a prehensile tail that is frequently employed in descending from
+small branches. Since cottonmouths are semi-aquatic and are often
+exposed to temperatures that are lower than those of the air, they
+either must bask more often than terrestrial snakes or tolerate lower
+temperatures. Length of the period of basking is determined not only by
+amounts of insolation and temperature but also by the size of the snake.
+A smaller snake can reach its optimum temperature more rapidly because
+of a higher surface-to-volume ratio. Another factor that may play a
+minor role in the rate of temperature change is the color of the snake.
+The wide variation in color of cottonmouths probably affects rates of
+heat increase and loss due to direct radiation. Slight hormonal control
+of melanophores described in snakes by Neill and Allen (1955) also may
+exert some influence on the length of time spent basking. No rates of
+temperature increase or decrease are available for cottonmouths.
+
+
+Coiling
+
+While inactive the cottonmouth spends most of its time lying in a coiled
+position with the tail outermost, with the body usually wound into about
+one and one-half cycles, and the head and neck in a reversed direction
+forming a U- or S-shaped loop. From this position the snake is able to
+make a short strike or a hasty getaway if necessary. In my opinion this
+position is used primarily for basking or resting and only secondarily
+for feeding. Most individuals appear to pursue their prey actively, not
+lying in ambush for the approaching prey to the extent that most other
+crotalids do.
+
+Many of the cottonmouths that I kept in captivity were observed in a
+coiled position for periods up to three or four days. Under natural
+conditions, however, they are more active. Young cottonmouths are
+inclined to remain in a coiled position for longer periods than older
+individuals.
+
+
+Locomotion
+
+Four distinct types of locomotion have been described in snakes:
+horizontal undulatory, rectilinear, sidewinding, and concertina
+(Klauber, 1956: 331-350). Most snakes are capable of employing two or
+more of these types of progression, at least to a certain degree; but
+horizontal undulatory locomotion is the most common method used by the
+majority of snakes, including the cottonmouth. In this method the
+snake's body is thrown into lateral undulations that conform with
+irregularities in the substrate. Pressure is exerted on the outside and
+posterior surface of each curve, thus forcing the body forward.
+
+Rectilinear locomotion is more useful to large, thick-bodied snakes
+which use this method of progression, chiefly when they are prowling and
+unhurried. This method depends upon the movement of alternate sections
+of the venter forward and drawing the body over the ventral scales
+resting on the substratum by means of muscular action. This mode of
+locomotion was most frequently observed in captive cottonmouths when
+they were crawling along the edge of their cages, especially when they
+were first introduced to the cages and toward the end of the shedding
+process. The other two types of locomotion, sidewinding and concertina,
+have not, to my knowledge, been observed in the cottonmouth.
+
+Both the cottonmouth and the cantil have definite affinities for water
+and are as likely to be found in water as out of it. Copperheads and
+rattlesnakes, although not aquatic, are good swimmers. When swimming, a
+motion resembling horizontal undulatory progression is used.
+
+
+Disposition
+
+The number of different opinions expressed in the literature concerning
+the cottonmouth's disposition is not at all surprising. As with any
+species there is a wide range of individual temperament, which is
+affected by many factors. The cottonmouth is considered by some writers
+to be docile while others consider it to be highly dangerous. Allen and
+Swindell (1948:7) described the variability in temperament, even among
+individuals. They wrote: "On rare occasions, moccasins are found which
+will attack. A perfectly docile snake will turn and bite viciously
+without any apparent reason." They also recounted a case in which a
+cottonmouth was kept as a pet for six years, being allowed the freedom
+of the house. Smith and List (1955:123) found them "... surprisingly
+docile in the gulf region [Mississippi], displaying none of the
+pugnacity of more northern cottonmouths." Smith (1956:310) stated:
+"Unlike the copperhead, cottonmouths are pugnacious; their powerful
+jaws, long fangs, vicious disposition and potent venom make them a very
+dangerous animal."
+
+My own observations are in general agreement with the statements of
+Allen and Swindell (_loc. cit._). In my encounters with cottonmouths, I
+have never found any aggressive individuals except for three juveniles
+that were born in captivity. In their first three days in the laboratory
+these juveniles were observed to strike repeatedly whenever anyone
+entered the room. After this short period of aggressiveness, however,
+they slowly became more docile. The disposition shown by the newborn
+young is clearly an innate behavioral pattern that undoubtedly has a
+direct relationship to survival. The majority of cottonmouths that I
+have approached in the field have moved swiftly to seek refuge in nearby
+water; a few have remained motionless as I approached, and one showed
+the typical threat display. Upon capture and handling, they react
+similarly to other pit-vipers by opening and closing the mouth and
+erecting the fangs in an attempt to bite. They often bite through the
+lower jaw and eject venom at this time as well as when the mouth is
+open. Of more than a dozen individuals kept in captivity, four were
+particularly difficult to handle whereas another was extremely docile.
+It was almost never found in aggregations with the other snakes and did
+not struggle or attempt to bite when handled. The majority remained
+unpredictable in disposition, usually appearing docile and lazy but
+capable of extremely rapid movements when disturbed.
+
+
+Defense and Escape
+
+The typical threatening posture of rattlesnakes is all but lacking in
+the cottonmouth, which relies primarily on concealing coloration or
+nearness to water for escape. When approached, it usually plunges into
+nearby water or remains motionless with the head held up at a 45 deg. angle
+and the mouth opened widely exposing the white interior. The tail is
+sometimes vibrated rapidly and musk is expelled. This threat display is
+unique to cottonmouths; although it does not attract as much attention
+as the display of rattlesnakes, it is probably an effective warning to
+most intruders at close range.
+
+Neill (1947:205) reported one case in which a cottonmouth used the "body
+blow" defense, described for _Crotalus_ by Cowles (1938:13), when
+approached by a king-snake, _Lampropeltis getulus_. In this unusual
+posture the anterior and posterior portions of the body are held against
+the ground and the middle one-fourth to one-third of the body is lifted
+up and used in striking the intruder. This same defense posture also was
+observed in rattlesnakes when presented with the odor of the spotted
+skunk, _Spilogale phenax_. However, the "king-snake defense posture" is
+probably not a well-established behavioral pattern in the cottonmouth,
+for it sometimes feeds upon king-snakes. I observed the killing and
+devouring of a cottonmouth by a speckled king-snake, _L. g. holbrooki_;
+the only attempts to escape were by rapid crawling and biting.
+
+Cottonmouths often squirt musk as a defensive action. The tail is
+switched back and forth, and musk is emitted from glands on each side of
+the base of the tail. The fine jets of musk are sprayed upward at about
+45 deg. angles for a distance of nearly five feet. How often this defense
+mechanism is used against other animals is not known, but the musky odor
+can frequently be detected in areas where cottonmouths are common. The
+odor is repulsive and, if concentrated, can cause nausea in some
+individuals. To me, the scent is indistinguishable from that of the
+copperhead.
+
+
+"Head Bobbing"
+
+"Head bobbing" in snakes has been described frequently in the
+literature, and many interpretations have been advanced to explain its
+occurrence. One of the earlier accounts was that of Corrington (1929:72)
+describing behavior of the corn snake, _Elaphe guttata_. Characteristic
+bobbing occurred when the snake was cornered, and seemingly the purpose
+was to warn or frighten foes. Neill (1949:114-115) mentioned the jerking
+or bobbing of the head in several species of snakes including the
+cottonmouth, and remarked that "it is apparently connected with
+courtship and with the recognition of individuals." According to Munro
+(1950:88), "head bobbing" appears to be a sign of annoyance in some
+instances but is usually concerned with reproduction and individual
+recognition. Richmond (1952:38) thought that many types of head
+movements among not only reptiles but also birds and some mammals are a
+result of poor vision and serve "to delimit and orient an object that
+for lack of motion is otherwise invisible." Head movements undoubtedly
+occur in animals to facilitate accommodation, but it is obvious from
+Richmond's conclusions that he has never observed "head bobbing" in
+snakes. The term itself is grossly misleading and should be discarded.
+Mansueti (1946:98) correctly described the movements as spastic
+contractions of the body. I have observed numerous instances of these
+movements in cottonmouths, copperheads, and rat snakes (_Elaphe
+obsoleta_); and in no case has the movement resembled a head bob as is
+described in lizards and other animals. The movement appears to be a
+result of a nervous or sexually excited state and consists of highly
+spastic contractions confined to the anterior part of the snake most of
+the time but affecting the entire body on some occasions.
+
+I found the response to be most common among cottonmouths in confinement
+when food was introduced to a cage containing several individuals
+(increasing the tendency to strike at a moving object) and when an
+individual was placed back in the cage after being handled. At these
+times the snakes that were inactive began to jerk for a few seconds.
+When the snake is in this seemingly nervous state, the same response is
+elicited by another snake crawling over it. At other times the movement
+of one individual causes no such response. The jerking movements appear
+to be released by the recognition of a nervous state in another
+individual and may serve to protect the jerking individual from
+aggressive advances of the former.
+
+Where courtship is involved, the jerking motions are made in conjunction
+with writhing of the male and do not result from the same type of
+releaser described above.
+
+
+Combat Dance
+
+The so-called combat dance between male snakes has long been known, but
+its significance is still poorly understood. It was for many years
+believed to be courtship behavior until the participants were examined
+and found to be males. Carr and Carr (1942:1-6) described one such
+instance in two cottonmouths as courtship. In their observations, as
+well as those of others, copulation was never observed following the
+"dance" but was assumed to be the ultimate goal. After the discovery
+that only males participated, it was suggested that combat involved
+competition for mates, but the "dance" has been observed at times other
+than the breeding season (Ramsey, 1948:228).
+
+Shaw (1948:137-145) discussed the combat of crotalids in some detail but
+drew no conclusions as to the cause of the behavior. Lowe (1948:134)
+concluded with little actual evidence that combat among male snakes is
+solely for territorial purposes. Shaw (1951:167) stated that combat may
+occur as a possible defense against homosexuality. One case of
+homosexual mating among cottonmouths was reported (Lederer,
+1931:651-653), but the incomplete description seems to be of normal
+courtship procedure except that the "female" tried to avoid the male.
+Two instances of combat observed between timber rattlesnakes (_C. h.
+horridus_) by Sutherland (1958:23-24) were definitely initiated because
+of competition for food. More observations are needed before the
+significance of the combat can be fully understood.
+
+
+
+
+THE VENOM
+
+Properties of the Venom
+
+
+The venom and poison apparatus have developed primarily as a means of
+causing rapid death in small animals that are the usual prey. As a
+protective device against larger enemies, including man, the venom may
+have some value; but this was probably unimportant in the evolution of
+the poison mechanism. A secondary function of the venom is to begin
+digestion of tissues of the prey. Since food is swallowed whole,
+injection of digestive enzymes into the body cavity enhances digestion
+of the prey.
+
+Kellogg (1925:5) described venom as a somewhat viscid fluid of a
+yellowish color and composed of 50 to 70 per cent proteins, the chief
+remaining components being water and carbohydrates, with occasional
+admixtures of abraded epithelial cells or saprophytic microorganisms.
+Salts, such as chlorides, phosphates of calcium, magnesium, and
+ammonium, occur in small quantities. Each of the components of snake
+venom has a different effect on the body of the victim. It was at first
+believed that there were two types of venoms: neurotoxic, which acts
+upon nervous tissue; and haemotoxic, which acts on blood and other
+tissues. It has since been found that venoms are composed of varying
+mixtures of both types. Fairley (1929:301) described the constituents of
+venom as: (1) neurotoxic elements that act on the bulbar and spinal
+ganglion cells of the central nervous system; (2) hemorrhagins that
+destroy the lining of the walls of blood vessels; (3) thrombose,
+producing clots within blood vessels; (4) hemolysins, destroying red
+blood corpuscles; (5) cytolysins that act on leucocytes and on cells of
+other tissues; (6) elements that retard coagulation of the blood; (7)
+antibactericidal substances; and (8) ferments that prepare food for
+pancreatic digestion. Elapid snakes tend to have more of elements 1, 4,
+and 6 in their venoms, while viperids and crotalids, of which the
+cottonmouth is one, have higher quantities of elements 2, 3, and 5.
+Kellogg (_loc. cit._) stated that venom of cottonmouths contains more
+neurotoxin than that of rattlesnakes and not only breaks down the nuclei
+of ganglion cells but also produces granular disintegration of the
+myelin sheath and fragmentation of the conducting portions of nerve
+fibers.
+
+Thus, venoms contain both toxic elements and non-toxic substances that
+promote rapid spreading of the venom through the body of the victim.
+Jacques (1956:291) attributed this rapid spreading to the hyaluronidase
+content of venoms.
+
+
+Venom Yield and Toxicity
+
+One of the most important yet undeterminable factors of the gravity of
+snakebite is the amount of venom injected into the victim. Since this
+volume varies considerably in every bite, attempts have been made to
+determine the amount and toxicity of venom produced by each species of
+poisonous snake. Individual yield is so variable that a large number of
+snakes must be milked in order to determine the average yield. Even then
+there remains an uncertainty as to how this amount may compare with that
+injected by a biting snake.
+
+Wolff and Githens (1939b:234) made 16 venom extractions from a group of
+cottonmouths in a two-year period. The average yield per snake
+fluctuated between 80 and 237 milligrams (actual weight), and toxicity
+measured as the minimum lethal dose for pigeons varied from 0.05 to 0.16
+milligrams (dry weight). No decrease in yield or toxicity was evident
+during this period. Another group of cottonmouths from which venom was
+extracted over a period of five years also showed no decrease in yield
+or toxicity. Of 315 individual extractions the average amount obtained
+from each individual was 0.55 cubic centimeters of liquid or 0.158 grams
+of dried venom (28.0 per cent solids). The minimum lethal dosage (M. L.
+D.) which was determined by injecting intravenously into 350-gram
+pigeons was found to be 0.09 milligrams (dry weight). Each snake carried
+approximately 1755 M. L. D.'s of venom.
+
+The record venom extraction for the cottonmouth was 4.0 cubic
+centimeters (1.094 grams dried venom) taken from a five-foot snake which
+had been in captivity for 11 weeks and milked five weeks earlier (Wolff
+and Githens, 1939a:52). The average yield of venom of cottonmouths is
+about three times the average yield reported for copperheads by Fitch
+(1960:256), a difference correlated with the greater bulk and relatively
+large head of the cottonmouth.
+
+Allen and Swindell (1948:13) stated that cottonmouth venom rates third
+in potency, compared drop for drop to that of _Micrurus fulvius_ and
+_Crotalus adamanteus_. Freshly dried cottonmouth venom tested on young
+white rats showed the lethal dose to be from 23 to 29 milligrams per
+kilogram of body weight. The venom of 11 one-week-old cottonmouths was
+found to be more potent than that of adult males. Githens (1935:171)
+rated _C. adamanteus_ venom as being weaker than that of the copperhead
+(_A. contortrix_), which he rated only slightly lower than cottonmouth
+venom. The crotalids which he ranked more toxic than cottonmouths are:
+the Pacific rattlesnake (_C. viridis oreganus_) and the massasauga (_S.
+catenatus_). He found _A. bilineatus_, _C. durissus_, and _C. v.
+lutosus_ to have the same toxicity as cottonmouths. Minton (1953:214)
+found that the intraperitoneal "lethal dose 50" (the dose capable of
+killing half the experimental mice receiving injections of it) was 6.36
+milligrams per kilogram for copperheads. However, in later publications
+Minton (1954:1079; 1956:146) reported that the "lethal dose 50" for
+copperheads was 25.65 milligrams. Approximately the same potency was
+determined for cottonmouths. Several rattlesnakes that he tested showed
+a higher toxicity than copperheads or cottonmouths.
+
+Criley (1956:378) found the venom of copperheads to be 6.95, nearer
+Minton's earlier estimate, and rated cottonmouth venom as being twice as
+toxic as that of copperheads. The relative toxicities of other crotalids
+tested, considering the cottonmouth to be one unit, were: _C.
+basiliscus_, 0.3; _A. contortrix_, 0.5; _C. viridis oreganus_, 1.4; _A.
+bilineatus_, 2.2; _C. adamanteus_, 2.3; _C. v. viridis_, 3.2; _C.
+durissus terrificus_, 27.5.
+
+It can be seen from the above examples that toxicity of venoms and the
+resistance of the animal receiving an injection of venom is highly
+variable. Possibly the venom of each species of snake has greatest
+effect on animals of the particular group relied on for food by the
+snake. If that is so, the venom of cottonmouths would be expected to be
+more toxic when tested on fish, reptiles, and amphibians than on birds
+and mammals. Likewise, the venom of most species of rattlesnakes would
+be expected to be more virulent when injected into mammals than when
+injected into lower vertebrates. But, according to Netting (1929:108),
+species of rattlesnakes that prey on cold-blooded animals, which are
+less susceptible to venoms than warm-blooded animals, are thought to
+have highly toxic venoms. This explanation accounts for the powerful
+venom of _Sistrurus catenatus_; and, in this respect, venom of
+cottonmouths should be highly toxic also. However, no clear-cut trends
+have been shown in most cases. Allen (1937) injected 250-gram guinea
+pigs with 4 milligrams of venom of various poisonous snakes. Survival
+time was recorded in order to indicate the relative potency of the
+venoms. Of 16 such tests _C. adamanteus_ held places 1, 2, 3, 12, and
+16; _Bothrops atrox_ held places 4, 9, 10, and 13; and _A. piscivorus_
+held places 5, 7, 8, and 15. Places 6, 11, and 14 were held by three
+individuals of different species. No relationship to size or sex was
+indicated by the results of this experiment.
+
+
+Susceptibility of Snakes
+
+Numerous experiments have been conducted to determine the susceptibility
+of various snakes to venom. The majority of these experiments were
+performed to learn whether or not venomous snakes were immune to their
+own poison. Conant (1934:382) reported on a 30-inch cottonmouth that
+killed two Pacific rattlesnakes and another cottonmouth. One rattlesnake
+was bitten on the tail and the other on or near the head and partially
+swallowed. Gloyd (1933:13-14) recorded fatal effects to a rattlesnake
+from the bite of a cottonmouth. He also reported on the observations of
+three other crotalids bitten by themselves or other snakes, from which
+no harmful effects were observed. Allen (1937) injected several snakes
+with dried cottonmouth venom which was diluted with distilled water just
+before each injection. Four cottonmouths receiving 9, 18, 19, and 20
+milligrams of venom per ounce of body weight survived, while another
+receiving 18.7 milligrams per ounce died after three hours. A specimen
+of _S. miliarius_ receiving 8.3 milligrams per ounce died in about ten
+hours, while a _C. durissus_ receiving 12.5 milligrams per ounce
+succumbed in 45 minutes. An alligator receiving 6 milligrams per ounce
+died in 14 hours. Even the snakes that survived showed some degree of
+swelling.
+
+The studies of Keegan and Andrews (1942:252) show that king-snakes are
+sometimes killed by poisonous snakes. A _Lampropeltis calligaster_
+injected with _A. contortrix_ venom (0.767 milligrams per gram) died
+five days following the injection. This amount was more than twice the
+amount of _A. piscivorus_ venom injected into a _L. getulus_ by Allen
+(1937) in which the snake showed no ill effects. Keegan and Andrews
+(_loc. cit._) stated that success in overpowering and eating poisonous
+snakes by _Lampropeltis_ and _Drymarchon_ may be due to the ability to
+avoid bites rather than to immunity to the venom. However, Rosenfeld and
+Glass (1940) demonstrated that the plasma of _L. g. getulus_ had an
+inhibiting effect on the hemorrhagic action on mice of the venoms of
+several vipers.
+
+One of the more extensive studies on effects of venoms on snakes is that
+by Swanson (1946:242-249). In his studies freshly extracted liquid venom
+was used. His studies indicated that snakes are not immune to venom of
+their own kind or to closely related species. Copperhead venom killed
+copperheads faster than did other venoms but took more time to kill
+massasaugas, cottonmouths, and timber rattlers. However, most of the
+snakes were able to survive normal or average doses of venom although
+they are not necessarily immune to it.
+
+One of the major problems in comparing the data on toxicity of venom in
+studies of this type is that no standard method of estimating toxicity
+has been used. Swanson's (_loc. cit._) amount of venom equalling one
+minim (M.L.D.?) ranged from 0.058 to 0.065 cubic centimeters. There were
+no different values given for each species, but the time that elapsed
+from injection of the venom to death represented the toxicity. There
+also was no attempt in his study to convert the amount of venom used
+into a ratio of the volume of venom per weight of snake, making the
+results somewhat difficult to interpret. Additional work in this field
+should provide for many injections into many individuals of several size
+classes. The studies to date have been on far too few individuals to
+allow statistical analyses to be accurate.
+
+
+
+
+THE BITE
+
+Effects of the Bite
+
+
+Factors determining the outcome of snakebite are: size, health, and
+species of snake; individual variation of venom toxicity of the species;
+age and size of the victim; allergic or immune responses; location of
+the bite; and the amount of venom injected and the depth to which it is
+injected. The last factor is one of the most variable, owing to (1)
+character and thickness of clothing between the snake and the victim's
+skin, (2) accuracy of the snake's strike, and (3) size of the snake,
+since a large snake can deliver more venom and at a greater depth than
+can a small snake.
+
+Pope and Perkins (1944) demonstrated that pit-vipers of the United
+States bite as effectively as most innocuous snakes and that a careful
+study of the bite may reveal the location of the pocket of venom, size
+of the snake, and possibly its generic identity (see Dentition). The
+bite pattern of the cottonmouth as well as the other crotalids showed
+the typical fang punctures plus punctures of teeth on both the pterygoid
+and mandible. Even so, a varying picture may be presented because from
+one to four fang marks may be present. At times in the fang-shedding
+cycle three and even four fangs can be in operation simultaneously.
+
+Various authors have attributed death of the prey to the following
+causes: paralysis of the central nervous system, paralysis of the
+respiratory center, asphyxiation from clotting of the blood, stoppage of
+the heart, urine suppression due to crystallized hemoglobin in the
+kidney tubules, dehydration of the body following edema in the area of
+the bite, or tissue damage. Mouths of snakes are reservoirs for
+infectious bacteria, which are especially prolific in damaged tissue.
+Bacterial growth is aided by the venom which blocks the bactericidal
+power of the blood.
+
+Three grades in the severity of snakebite (I, minimal; II, moderate; and
+III, severe) were described by Wood, Hoback, and Green (1955). Parrish
+(1959:396) added a zero classification to describe the bite of a
+poisonous snake in which no envenomation occurred. Grade IV (very
+severe) was added by McCollough and Gennaro (1963:961) to account for
+many bites of the eastern and western diamondback rattlesnakes.
+
+The first symptom of poisonous snakebite is an immediate burning
+sensation at the site of the bite. Within a few minutes the loss of
+blood into the tissues causes discoloration. Swelling proceeds rapidly
+and can become so great as to rupture the skin. Pain is soon felt in the
+lymph ducts and glands. Weakness, nausea, and vomiting may ensue at a
+relatively early stage. Loss of blood into tissues may spread to the
+internal organs. In conjunction with a rapid pulse, the blood pressure
+and body temperature can drop. Some difficulty in breathing can occur,
+especially if large amounts of neurotoxin are present in the venom. In
+severe cases the tension due to edema obstructs venous and even arterial
+flow, in which case bacteria may multiply rapidly in the necrotic tissue
+and gangrene can occur. Blindness due to retinal hemorrhages may occur.
+Symptoms of shock may be present after any bite.
+
+
+Treatment
+
+Perhaps one of the most important factors in the outcome of snakebite is
+the treatment. Because of the variable reactions to snakebite, treatment
+should vary accordingly. Many methods have been proposed for treating
+snakebite, and there is disagreement as to which is the best. The list
+of remedies that have been used in cases of snakebite includes many that
+add additional injury or that possibly increase the action of the venom.
+The use of poultices made by splitting open living chickens and the use
+of alcohol, potassium permanganate, strychnine, caffeine, or injection
+of ammonia have no known therapeutic value, and may cause serious
+complications. The most important steps in the treatment of snakebite
+are to prevent the spread of lethal doses of venom, to remove as much
+venom as possible, and to neutralize the venom as quickly as possible.
+
+It is generally agreed that the first step in snakebite treatment should
+be to place a ligature above the bite to restrict the flow of venom, and
+also to immobilize the patient as much as possible. The ligature should
+be loosened at least every fifteen minutes. The next steps are
+sterilization of the skin and the making of an incision through the fang
+punctures. As pointed out by Stahnke (1954:8), the incision should be
+made in line with the snake's body at the time of the bite, so as to
+account for the rearward curvature of the fangs and possibly to reach
+the deposition of venom. Many instruction booklets and first-aid guides
+have specified the length and depth of incision to be made, but the
+actual size and depth of the cut should depend upon the location of the
+bite. An "X" cut or connection of the fang punctures is likely to
+facilitate the spread of the venom. No cut should be made that would
+sever a large blood vessel or ligament.
+
+Extensive damage is often caused by well-meaning individuals whose
+attempts at first aid result in brutally deep incisions and tourniquets
+applied too tightly and for too long a period of time; the resultant
+damage in many instances exceeds that of the bite itself (Stimson and
+Engelhardt, 1960:165). Stimson and Engelhardt also think that time
+should be sacrificed to surgical cleanliness, and incisions should not
+be made if a hospital can be reached within an hour.
+
+The ligature-cryotherapy (L-C) method proposed by Stahnke (1953) has
+been severely criticized by other workers. He stated that the ligature
+should be tight enough to restrict completely the flow of venom until
+the temperature of the area can be lowered sufficiently to prevent any
+action of the venom. After 10 minutes the ligature may be removed and
+the bitten area kept immersed in a vessel of crushed ice and water. If
+the envenomized member is to be treated for more than four hours (which
+is the case with almost all pit-viper bites), it should be protected by
+placing it in a plastic bag. The venom action should be tested after 12
+or more hours. This consists of a brief warming period to determine
+whether or not the action of the venom can be felt. The patient should
+be kept warm at all times; and the warming at the termination of
+treatment should be done gradually, preferably by allowing the water to
+warm slowly to room temperature.
+
+Advocates of the L-C method warn against making incisions unless they
+are absolutely necessary, the theory being that each cut permits
+additional bacterial infection and does little good in removing venom.
+However, McCollough and Gennaro (1963:963) demonstrated that, in bites
+where the fangs had only slightly penetrated the skin, more than 50 per
+cent of the venom was removed in some instances if suction was started
+within three minutes after the injection. With deeper injection the
+amount of venom recovered sometimes reached 20 per cent of the dose.
+Stahnke suggested that an incision be made at the site of the bite only
+after the site has been refrigerated for at least 30 minutes.
+
+Stimson and Engelhardt (_loc. cit._) stated that two constricting bands
+should be used between the bite and the body and that cracked ice in a
+cloth should be applied to the bite before reaching a hospital. In
+addition, they suggested the following procedure. Rings of incisions
+should follow the swelling, and suction should continue for several
+hours. After the edema has receded, the limb should be wrapped in a
+towel containing crushed ice. Antivenin should be given only in severe
+cases. Calcium gluconate and gas gangrene antitoxin as well as
+antibiotics are helpful.
+
+The most recent and up-to-date summary of snakebite treatment is that by
+McCollough and Gennaro (1963). Following is a brief summary of their
+suggestions:
+
+     1. Immobilization--Systemic immobilization is effected by body
+     rest and locally by splinting the bitten area.
+
+     2. Tourniquet--A lightly occlusive tourniquet during a 30- to
+     60-minute period of incision and suction would seem to possess
+     some advantages. In severe cases where medical attention is
+     hours away, a completely occlusive tourniquet may be necessary
+     to prevent death. Sacrifice of the extremity may be necessary
+     for the preservation of life.
+
+     3. Incision and suction--Suction should begin three to five
+     minutes after injection of venom if symptoms of poisoning are
+     present. Incisions one-fourth inch to an inch long across each
+     fang mark should be made in order to open the wound for more
+     efficient suction. Multiple incisions are not useful for the
+     removal of venom but may be employed under hospital conditions
+     to reduce subcutaneous tensions and ischemia.
+
+     4. Cryotherapy--An ice cap over the site of the bite for relief
+     of pain would seem to be permissible, especially prior to the
+     administration of antivenin. It must be remembered that cooling
+     during the administration of the antivenin radically reduces
+     the access of the antiserum to the bite area.
+
+     5. Antivenin--Antiserum is the keystone to the therapy of
+     snakebite. Careful evaluation of the severity of the bite and
+     the patient's sensitivity should be made before the use of
+     antivenin. In Grade II (moderate) bites, the intramuscular
+     injection on the side of the bite may suffice. In Grades III
+     (severe) and IV (very severe), shock and systemic effects
+     require intravenous injection. In bites producing symptoms of
+     this severity, antivenin must be given in amounts large enough
+     to produce clinical improvement. Ten to 20 units may be
+     necessary to prevent the relapse that sometimes occurs after
+     small doses of antivenin. Permanent remission of swelling and
+     interruption of necrosis are the therapeutic end point in the
+     clinical use of the antiserum.
+
+In all cases of snakebite where there is any doubt as to the snake's
+identity, it should be killed if possible and taken to the hospital for
+positive identification. In many instances of actual bites by poisonous
+snakes the only treatment needed was an injection of tetanus antitoxin
+or toxoid and sedation, because physical examination revealed no
+indication of poisoning (Stimson and Engelhardt, _loc. cit._).
+
+
+Case History of a Bite
+
+On July 29, 1963, at 8:20 a.m., I was treating a nine-month-old
+cottonmouth for mites. As I dropped the snake into a sink, it twisted
+its head and bit the tip of my right middle finger with one fang. The
+fang entered just under the fingernail and was directed downward, the
+venom being injected about five millimeters below the site of fang
+penetration. After placing the snake back in its cage, I squeezed the
+finger once to promote bleeding, wrapped a string around the base of the
+finger, and drove to Watkins Memorial Hospital on the University of
+Kansas campus. I began to feel a burning sensation in the tip of the
+finger almost immediately. Upon my arrival at the hospital, an
+additional ligature was placed around my wrist. At 8:30 a.m. a small
+incision was made in the end of the finger, which by this time was
+beginning to darken at the point of venom deposition. I sucked on the
+finger until 8:35 a.m., when a pan of ice water that I had requested was
+brought to me. No pain was felt except that caused by the ice. Fresh ice
+was added as needed to keep the temperature low. By 9:30 a.m. the
+finger had swollen and stiffened. At 10:00 a.m. the swelling had
+progressed to the index finger and back of the hand. I experienced
+difficulty in opening and closing the hand. Blood oozed slowly from the
+incision. A dull ache persisted and about every two to four minutes a
+sharp throb could be felt until nearly 11:00 a.m., when the pain
+diminished. The rate and intensity of throbbing increased whenever the
+hand was removed from the ice bath for more than a few seconds. Although
+only the hand was immersed, the entire forearm was cold. Pain was felt
+along the lymphatics on top of the arm when it was touched, and by 1:00
+p.m. a slight pain could be felt in the armpit. Since swelling and pain
+were almost nonexistent by 2:00 p.m., I was permitted to leave. After
+walking to a nearby building, I again felt a burning sensation as the
+hand warmed. I made another ice bath and again immersed the hand in it
+until 4:10 p.m., at which time it was removed from the water. The pain
+and swelling began anew, and the hand was placed back in an ice bath
+from 5:30 p.m. until about 7:30 p.m. At this time cryotherapy was
+discontinued. From 10:00 p.m. to 12:00 midnight my legs twitched
+periodically, and pain could be felt in both armpits. A slight
+difficulty in breathing also was experienced for a short time. The acute
+pain and burning sensation remained in the finger until the following
+morning, but swelling progressed only as far as the wrist. The only
+discomfort that day was in the finger. The tip was darkened, the entire
+first digit red and feverish, and the lymphatics still painful when
+touched. By the third day the swelling had regressed. The incision
+itself was the main cause of discomfort, and the soreness at the site of
+the bite persisted for at least four days.
+
+Although the L-C method of snakebite treatment has been vigorously
+attacked by many, there is still need of much more data before it
+can be unequivocally condemned or praised. It was preferred in the
+treatment of this bite because: I knew that envenomation was minimal
+and that there would be no need for antivenin; only one fang of a
+snake less than one foot long had entered the tip of the finger; the
+snake had bitten three frogs in the previous two days and had
+possibly used up a considerable amount of its venom; the venom was
+deposited at such a shallow depth that at least a portion of it
+could be removed by suction; and the wound bled freely even before
+suction was applied. The ice water was uncomfortably cold but was
+not cold enough to cause frostbite, a major objection to the L-C
+method. Ideally, fresh ice should be added little by little to
+replace that which is melting, and the immersed area should be
+protected from the water by a plastic bag. Pain and swelling can be
+minimized by cryotherapy, but I would recommend its use only in
+cases of mild poisoning such as the one described herein.
+
+
+Snakebite in the United States
+
+Many estimates have been made of the number of bites of poisonous snakes
+that occur annually in the United States. The occurrence of poisonous
+snakebite has been nearly as badly underestimated as fatal results of
+their envenomations have been overrated. For important data on number of
+persons bitten by poisonous snakes in the United States, see the
+following: Allen and Swindell (1948:15); Githens (1935:172); Klauber
+(1956:811); Parrish (1963); Sowder and Gehres (1963:973); Stimson and
+Engelhardt (1960:153); Swaroop and Grab (1956:441); Swartzwelder
+(1950:579); Willson (1908:530); and Wood (1954b:937).
+
+Judging from estimates made in several states, the number of poisonous
+snakebites in the United States would be about 5000 per year. In the
+region where the cottonmouth occurs there are approximately 2000 persons
+bitten annually by poisonous snakes. Of these approximately 39 per cent
+are copperhead bites, 30 per cent each are cottonmouth and rattlesnake
+bites, and I per cent are coral snake bites. These percentages vary
+considerably from place to place, because of the distribution and
+abundance of the eight species of poisonous snakes whose ranges overlap
+that of the cottonmouth.
+
+According to Parrish (1963), about 14 people die of snakebite each year
+in the United States. Of these deaths, about 6.6 per cent are
+attributable to cottonmouths, 77.0 per cent to rattlesnakes, and 1.6 per
+cent to coral snakes; 14.8 per cent are unidentified. Almost half of the
+fatalities are in persons less than 20 years of age, the high mortality
+rate being partially due to the greater ratio of venom to body weight.
+
+
+
+
+SUMMARY
+
+
+In my study, 306 living and preserved cottonmouths were examined. This
+species occurs throughout the coastal plains of the southeastern United
+States, usually at altitudes of less than 500 feet but occasionally up
+to altitudes of more than 2000 feet.
+
+Two subspecies are recognized: the eastern cottonmouth, _A. p.
+piscivorus_, occurring from extreme eastern Mississippi to southeastern
+Virginia and Florida; and the western cottonmouth, _A. p. leucostoma_,
+occurring from eastern Mississippi northward to southern Illinois and
+Missouri and westward to central Texas. Intergradation occurs in eastern
+Mississippi.
+
+The northern edge of the range is probably limited by low temperatures
+in winter, and the western edge by lack of available habitat resulting
+from insufficient precipitation. Old records of occurrence indicate that
+the range has decreased in the last 100 years. The species inhabits
+mostly areas where water is found, but at times wanders a mile or more
+from the nearest water.
+
+The ground color is predominantly a brown, but varies from a
+brownish-green to almost black with a pattern of 10 to 17 irregular
+bands of a darker shade of brown. The pattern is better defined in the
+eastern subspecies than in the western.
+
+The scutellation resembles that of other species of _Agkistrodon_. In
+the specimens examined supralabials ranged from 7 to 9, and infralabials
+from 8 to 12. The number of dorsal scale rows on the neck, at mid-body,
+and immediately anterior to the anus is relatively constant at 27-25-21,
+respectively. Ventral scales of 34 males averaged 134.4 (128 to 139),
+and those of 48 females 133.5 (128 to 137). The number of caudal scales
+showed some degree of sexual dimorphism; the average was 45.4 (41 to 50)
+in 34 males and 42.6 (39 to 49) in 44 females. In general, caudal scales
+on the basal half of the tail are undivided, whereas those on the distal
+half are divided. No marked geographical variation was found in any
+scale character.
+
+The poison fangs vary in length from 1.3 per cent of snout-vent length
+in juveniles to 1.0 per cent in large adults. Fangs of captive
+cottonmouths were shed and replaced at intervals of about 21 days, but
+the interval was variable. Relationships in distance between the base of
+fangs and between fang punctures in an actual bite indicate that
+examination of the wound does not provide a good basis for judging
+accurately the size of the snake that inflicted the bite.
+
+In general, females less than 450 millimeters in snout-vent length were
+juveniles; those more than 450 millimeters were classified as post
+partum or reproductive on the basis of sizes of ovarian follicles. Since
+about half the adult females were fecund, it was concluded that a
+biennial reproductive cycle occurs in this species. An annual cycle may
+occur in areas where temperature permits year-round activity. It was
+estimated that females become sexually mature at an age of approximately
+two and one-half years. Mating is probably most concentrated in early
+spring at about the time when females ovulate, but copulation is not a
+stimulus for ovulation. Sperm retention and delayed fertilization allow
+young to be produced without copulation occurring in each breeding
+season. The testes increase in size gradually rather than rapidly at
+maturity or in each breeding season, but seasonal cycles in sperm
+production occur.
+
+The gestation period is three and one-half to four months. Determination
+of sex in the embryos is possible by late June, because the hemipenes of
+males are evaginated until the time of birth. Parturition generally
+occurs in August or September, but captivity may delay birth for a month
+or more. From one to 16 young per litter are born, depending on size of
+the mother and other factors; but the average is between six and seven.
+Mortality rate at birth is high in captive individuals but has not been
+determined in natural populations. The sex ratio in embryos and adults
+examined revealed about 53 per cent females. Because sufficient
+information on population composition is not available, an estimate of
+the percentage of adults in a natural population was based upon the
+number found in my study. The reproductive potential was estimated from
+these figures.
+
+Normal young at birth are 230 to 240 millimeters in snout-vent length,
+but their size is influenced by the condition of the mother. Comparison
+of newborn young with those captured in spring indicates that little
+growth occurs during winter. Early growth is largely dependent upon
+feeding before winter quiescence.
+
+The umbilical cord is broken at birth and the navel closes within a few
+days, but the scar remains throughout life. Sexual dimorphism in the
+position of the scar is characteristic of some snakes but is minimal in
+cottonmouths.
+
+In those snakes more than 700 millimeters in length, males outnumber
+females three to one. The maximum age of cottonmouths in nature is
+unknown, but one has been kept in captivity for more than 18 years.
+
+Allometric growth is striking in cottonmouths. The head and tail are
+proportionately longer in young individuals than in adults; and in males
+the tail is, on the average, slightly longer than in females of the same
+size.
+
+Shedding of the skin provides for growth and wear in snakes. The young
+shed within a few days after birth and generally shed more frequently
+than adults. Frequency of shedding depends mostly on amount of food
+consumed, and there is some evidence that injuries on the head and neck
+increase the frequency of shedding. Before shedding, the eyes become
+cloudy for about five and one-half days, then clear up again for about
+four days before the skin is shed.
+
+The food of cottonmouths consists mainly of small vertebrates and
+occasionally invertebrates that are found near water. Fish, amphibians,
+and reptiles make up nearly 70 per cent of the diet. Carrion is also
+eaten and cannibalism occurs occasionally. Food is obtained by lying in
+ambush or by active searching. The young are known to lure their prey
+within striking range by waving their yellow tails in a manner
+suggestive of writhing grubs. The method of obtaining prey differs
+according to the kind of prey. Generally, cottonmouths retain their hold
+on fish or frogs but release mice and larger prey after delivering a
+bite.
+
+The major causes of mortality of cottonmouths are obscure. Predators are
+known to include alligators, indigo snakes, king-snakes, largemouth
+bass, and blue herons; there are probably numerous others. Heavy
+parasitic infestations were found among the snakes examined. Snake
+mites, _Ophionyssus natricus_, became increasingly abundant on almost
+all captive snakes in April and May of 1963. Lung flukes (_Ochetosoma_
+sp.) were in 16 of 20 captive snakes, and many preserved specimens
+contained nematodes (_Kalicephalus_ sp.) in the stomach and/or tapeworms
+(_Ophiotaenia_ sp.) in the intestine. Although parasitic infestation
+causes discomfort and may lower resistance to other detrimental factors,
+it is difficult to attribute death to the effect of any particular kind
+of parasite. Miscellaneous causes of death of some captive snakes also
+were discussed.
+
+The maximal body temperatures tolerated by four cottonmouths were
+between 38 deg. and 40 deg. C., but a temperature of 38 deg. was lethal to a fifth
+individual. Cottonmouths have been found on occasion when other snakes
+were inactive because of low temperatures, but minimal temperatures
+tolerated by this species are not known. The annual cycle of activity is
+dependent upon temperature and thus varies from north to south.
+Cottonmouths generally migrate inland in autumn, usually to dry forested
+hillsides, where they den along with other species of snakes. After a
+few warm days in spring they migrate back to the water's edge. The diel
+activity cycle likewise depends upon temperatures but is influenced by
+other factors as well. In spring and autumn, the snakes are active
+mostly on warm, sunny days, whereas in summer they are active mostly at
+night. In order to maintain adequate internal temperatures, much time is
+spent basking mostly in a characteristic flat, resting coil either
+beside a body of water or above water on limbs of dead trees. In this
+position the snake is ready either for a short strike or a hasty
+getaway.
+
+Juveniles appear particularly aggressive and strike repeatedly when
+approached, a behavioral pattern definitely favoring survival. Adults
+vary in disposition, usually appearing sluggish and lazy, but they are
+capable of striking rapidly when disturbed. The typical threat display
+consists of lying in a coiled position with the mouth opened widely,
+exposing the white interior, and with the tail vibrating rapidly. The
+striking posture resembles the resting coil except that the anterior
+part of the body is raised off the ground and the mouth is sometimes
+opened. Musk is often ejected in a fine spray from glands in the tail as
+a further defensive action.
+
+"Head bobbing," more properly described as spastic contractions of the
+body, was observed in captives when food was introduced into a cage
+containing several individuals or when one of the snakes was returned to
+the cage after being handled. Reports in the literature also have
+connected these jerking movements with courtship. The response appears
+to be elicited whenever a nervous state is recognized in another
+individual and may serve to protect the jerking individual from
+aggressive advances of the former.
+
+The relatively heavy appearance of the body, sluggish habits, and
+cryptic coloration are correlated with the development of venom and
+fangs. The poison apparatus has developed primarily as a means of
+causing rapid death in prey and secondarily, perhaps, to begin the
+digestion of small animals that are the usual prey, but it is also
+important as a defensive device. The venom contains at least eight
+constituents that aid in its action on prey. Toxicity of the venom is
+difficult to determine because of numerous variables, but cottonmouth
+venom is generally believed to be less potent than that of most
+rattlesnakes and more potent than that of the copperhead. Snakes in
+general are more resistant to snake venoms than other vertebrates of
+similar size, but there is no immunity even to their own venom.
+
+About ten per cent of the approximately 5000 bites of poisonous snakes
+per year in the United States are attributable to cottonmouths, and
+about seven per cent of the approximately 14 deaths per year are caused
+by cottonmouths.
+
+
+
+
+LITERATURE CITED
+
+
+ALLEN, E. R.
+
+     1937. Florida snake venom experiments. Florida Acad. Sci., 2:7 pp.
+
+ALLEN, E. R., and SWINDELL, D.
+
+     1948. Cottonmouth moccasin of Florida. Herpetologica, 4:1-16 (first
+     supplement).
+
+ALLEN, M. J.
+
+     1932. A survey of the amphibians and reptiles of Harrison County,
+     Mississippi. Amer. Mus. Novit., 542:1-20.
+
+ANDERSON, P.
+
+     1941. The cottonmouth in northern Missouri. Copeia, 1941(3):178.
+
+     1945. New herpetological records for Missouri. Bull. Chicago Acad.
+     Sci., 7(5):271-275.
+
+ANON.
+
+     1953. Snake collecting hobby of Colonial Heights lad. Virginia
+     Wildlife, 14-24.
+
+AUFFENBERG, W.
+
+     1963. The fossil snakes of Florida. Tulane Studies Zool.,
+     10(3):131-216, 51 figs.
+
+BAILEY, R. M.
+
+     1948. Winter mortality in the snake _Storeria dekayi_. Copeia,
+     1948(3): 215.
+
+BARBOUR, R. W.
+
+     1956. A study of the cottonmouth, _Agkistrodon piscivorus
+     leucostoma_ Troost, in Kentucky. Trans. Kentucky Acad. Sci.,
+     17(1):33-41, 1 fig.
+
+BLANCHARD, F. N.
+
+     1922. The amphibians and reptiles of western Tennessee. Occ. Pap.
+     Mus. Zool.; Univ. Michigan, 117:1-18.
+
+BOGERT, C. M.
+
+     1943. Dentitional phenomena in cobras and other elapids with notes
+     on adaptive modifications of fangs. Bull. Amer. Mus. Nat. Hist.,
+     81(3):285-360.
+
+BRATTSTROM, B. H.
+
+     1954. The fossil pitvipers (Reptilia: Crotalidae) of North America.
+     Trans. San Diego Soc. Nat. Hist., 12(3):31-46, 2 figs.
+
+BROWN, A. E.
+
+     1903. Texas reptiles and their faunal relations. Proc. Acad. Nat.
+     Sci. Philadelphia, pp. 543-558.
+
+CARPENTER, C. C.
+
+     1958. Reproduction, young, eggs, and food of Oklahoma snakes.
+     Herpetologica, 14:113-115.
+
+CARR, A. F., JR.
+
+     1936. The gulf-island cottonmouths. Proc. Florida Acad. Sci.,
+     1:86-90.
+
+CARR, A. F., JR., and CARR, M. H.
+
+     1942. Notes on the courtship of the cottonmouth moccasin. Proc. New
+     England Zool. Club, July 18, 20:1-6.
+
+CLARK, R. F.
+
+     1949. Snakes of the hill parishes of Louisiana. Jour. Tennessee
+     Acad. Sci., 24(4):244-261.
+
+CONANT, R.
+
+     1933. Three generations of cottonmouths, _Agkistrodon piscivorus_
+     (Lacepede). Copeia, 1933(1):43.
+
+     1934. Two rattlesnakes killed by a cottonmouth. Science,
+     80(2078):382.
+
+     1958. A field guide to reptiles and amphibians. Houghton Mifflin
+     Co., Boston, 366 pp.
+
+COOK, F. A.
+
+     1962. Snakes of Mississippi. Mississippi Game and Fish Comm., Surv.
+     Bull., ii + 45 pp.
+
+CORRINGTON, J. D.
+
+     1929. Herpetology of the Columbia, South Carolina region. Copeia,
+     1929:58-83.
+
+COWLES, R. B.
+
+     1938. Unusual defense postures assumed by rattlesnakes. Copeia,
+     1938(1):13.
+
+COWLES, R. B., and BOGERT, C. M.
+
+     1944. A preliminary study of the thermal requirements of desert
+     reptiles. Bull. Amer. Mus. Nat. Hist., 83(5):263-296.
+
+CRILEY, B. R.
+
+     1956. Development of a multivalent antivenin for the family
+     Crotalidae. Pp. 373-380 _in_ Venoms (ed. Buckley, E. E., and
+     Porges, N., Amer. Assoc. Adv. Sci., Publ. No. 44).
+
+DARLINGTON, P. J.
+
+     1957. Zoogeography: the geographical distribution of animals. John
+     Wiley and Sons, Inc., New York, xi + 675 pp.
+
+DAVIS, D. D.
+
+     1936. Courtship and mating behavior in snakes. Zool. Series Field
+     Mus. Nat. Hist., 20:257-290, figs. 28-34.
+
+DIDISHEIM, P., and LEWIS, J. H.
+
+     1956. Fibrinolytic and coagulent activities of certain snake venoms
+     and proteases. Proc. Soc. Exp. Biol. Med., 93(1):10-13.
+
+DITMARS, R. L.
+
+     1915. The reptile book. Doubleday, Page and Co., Garden City, N.
+     Y., xxxii + 472 pp.
+
+     1945. The reptiles of North America. Doubleday, Doran and Co.,
+     Inc., Garden City, N. Y., xvi + 476 pp., 135 pls.
+
+DOWLING, H. G.
+
+     1951a. A proposed standard system of counting ventrals in snakes.
+     British Jour. Herp., 1(5):97-98, 1 fig.
+
+     1951b. A proposed method of expressing scale reductions in snakes.
+     Copeia, 1951(2):131-134.
+
+DUNDEE, H. A., and BURGER, W. L., JR.
+
+     1948. A denning aggregation of the western cottonmouth. Nat. Hist.
+     Misc., Chicago Acad. Sci., 21:1-2.
+
+EDGREN, R. A.
+
+     1951. The umbilical scar, a sexually dimorphic character in
+     _Heterodon platyrhinos_. Nat. Hist. Misc., 83:1-2.
+
+FAIRLEY, N. H.
+
+     1929. The present position of snake bite and the snake bitten in
+     Australia. Med. Jour. Australia, 1(10):296-313.
+
+FITCH, H. S.
+
+     1956. Temperature responses in free-living amphibians and reptiles
+     in northeastern Kansas. Univ. Kansas Publ. Mus. Nat. Hist.,
+     8(7):417-476, 10 figs., 6 tables.
+
+     1960. Autecology of the copperhead. Univ. Kansas Publ. Mus. Nat.
+     Hist., 13(4):85-288, pls. 13-20, 26 figs.
+
+FORCE, E. R.
+
+     1930. The amphibians and reptiles of Tulsa County, Oklahoma, and
+     vicinity. Copeia, 1930(2):25-39.
+
+FOX, W.
+
+     1948. Effect of temperature on development of scutulation in the
+     garter snake, _Thamnophis elegans atratus_. Copeia,
+     1948(4):252-262.
+
+GITHENS, T. S.
+
+     1935. Studies on the venoms of North American pit vipers. Jour.
+     Immun., 29(2):165-173.
+
+GLISSMEYER, H. R.
+
+     1951. Symposium. A snake den in Tooele County, Utah. Egg production
+     of the great basin rattlesnake. Herpetologica, 7(1):24-27.
+
+GLOYD, H. K.
+
+     1933. On the effects of moccasin venom upon a rattlesnake. Science,
+     78(2010):13-14.
+
+     1934. Studies on the breeding habits and young of the copperhead,
+     _Agkistrodon mokasen_ Beauvois. Papers Michigan Acad. Sci., Arts
+     and Letters, 19:587-604.
+
+GLOYD, H. K., and CONANT, R.
+
+     1943. A synopsis of the American forms of _Agkistrodon_
+     (copperheads and moccasins). Bull. Chicago Acad. Sci.,
+     7(2):147-170, 16 figs.
+
+GOODMAN, J. D.
+
+     1958. Material ingested by the cottonmouth, _Agkistrodon
+     piscivorus_, at Reelfoot Lake, Tennessee. Copeia, 1958(2):149.
+
+GUIDRY, E. V.
+
+     1953. Herpetological notes from southeastern Texas. Herpetologica,
+     9:49-56.
+
+HALL, H. H., and SMITH, H. M.
+
+     1947. Selected records of reptiles and amphibians from southeastern
+     Kansas. Trans. Kansas Acad. Sci., 49(4):447-454.
+
+HAMILTON, W. J., JR., and POLLACK, J. A.
+
+     1955. The food of some crotalid snakes from Fort Benning, Georgia.
+     Nat. Hist. Misc., 140:1-4.
+
+HERALD, E. S.
+
+     1949. Effects of DDT oil solution upon amphibians and reptiles.
+     Herpetologica, 5(6):117-120.
+
+HICKMAN, C. P.
+
+     1922. A northern record for the water moccasin. Copeia,
+     1922(106):39.
+
+HURTER, J. H.
+
+     1897. A contribution to the herpetology of Missouri. Trans. Acad.
+     Sci. St. Louis, 7:499-503.
+
+JACQUES, R.
+
+     1956. The hyaluronidase content of animal venoms. Pp. 291-293 _in_
+     Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv. Sci.,
+     Publ. No. 44).
+
+KEEGAN, H. L., and ANDREWS, T. F.
+
+     1942. Effects of crotalid venom on North American snakes. Copeia,
+     1942:251-254.
+
+KELLOGG, R.
+
+     1925. Poisonous snakes of the United States. U. S. D. A. Papers
+     (371), 13 pp.
+
+KLAUBER, L. M.
+
+     1941. Four papers on the application of statistical methods to
+     herpetological problems. Bull. Zool. Soc. San Diego, 17:1-95.
+
+     1956. Rattlesnakes. Univ. California Press, 2 vols., xxix + 1476
+     pp.
+
+KLIMSTRA, W. D.
+
+     1959. Food habits of the cottonmouth in southern Illinois. Chicago
+     Acad. Sci., Nat. Hist. Misc., 168:1-8.
+
+LAUGHLIN, H. E.
+
+     1959. Stomach contents of some aquatic snakes from Lake McAlester,
+     Pittsburgh County, Oklahoma. Texas Jour. Sci., 11(1):83-85.
+
+LEDERER, G.
+
+     1931. Aus meinem Tagebuch. Wachenschrift fur Aquar. und Terr'kde.,
+     28:651-653.
+
+LEE, H. T.
+
+     1964. Letters to the Editor, Texas Game and Fish Mag., 22(3):32.
+
+LOWE, C. H., JR.
+
+     1948. Territorial behavior in snakes and the so-called courtship
+     dance. Herpetologica, 4(4):129-145.
+
+MANSUETI, R.
+
+     1946. Mating of the pilot blacksnake. Herpetologica, 3:98-100, 1
+     fig.
+
+MARTIN, J. R., and WOOD, J. T.
+
+     1955. Notes on the poisonous snakes of the Dismal Swamp area.
+     Herpetologica, 11(3):237-238.
+
+MCCOLLOUGH, N. C., and GENNARO, J. F., JR.
+
+     1963. Evaluation of venomous snake bite in the southern United
+     States from parallel clinical and laboratory investigations. Jour.
+     Florida Med. Assn., 49(12):959-967.
+
+MCILHENNY, E. A.
+
+     1935. The alligator's life history. The Christopher Publ. House,
+     Boston, Massachusetts, 117 pp.
+
+MINTON, S. A., JR.
+
+     1953. Variation in venom samples from copperheads (_Agkistrodon
+     contortrix mokeson_) and timber rattlesnakes (_Crotalus horridus
+     horridus_). Copeia, 1953:212-215.
+
+     1954. Polyvalent antivenin in the treatment of experimental snake
+     venom poisoning. Amer. Jour. Trop. Med. and Hyg., 3:1077-1082.
+
+     1956. Some properties of North American pit viper venoms and their
+     correlation with phylogeny. Pp. 145-151 _in_ Venoms (ed. Buckley,
+     E. E., and Porges, N., Amer. Assoc. Adv. Sci., Publ. No. 44).
+
+MUNRO, D. F.
+
+     1949. Effect of DDT powder on small cottonmouths. Herpetologica,
+     5:71-72.
+
+     1950. Additional observations on head bobbing by snakes.
+     Herpetologica, 6:88.
+
+NEILL, W. T.
+
+     1947. Size and habits of the cottonmouth moccasin. Herpetologica,
+     3:203-205.
+
+     1949. Head bobbing, a widespread habit of snakes. Herpetologica,
+     5:114-115.
+
+     1960. The caudal lure of various juvenile snakes. Quart. Jour.
+     Florida Acad. Sci., 23(3):173-200, 2 figs.
+
+NEILL, W. T., and ALLEN, E. R.
+
+     1955. Metachrosis in snakes. Quart. Jour. Florida Acad. Sci.,
+     18(3):207-215.
+
+NETTING, M. G.
+
+     1929. The venom of _Sistrurus catenatus_. Bull. Antivenin Inst.
+     Amer., 2(4):108-109.
+
+PARRISH, H. M.
+
+    1959. Poisonous snakebites resulting in lack of venom poisoning.
+    Virginia Med. Month, 86:396-401.
+
+    1963. Analysis of 460 fatalities from venomous animals in the
+    United States. Amer. Jour. Med. Sci., 245(2):35-47.
+
+PARRISH, H. M., and POLLARD, C. B.
+
+     1959. Effects of repeated poisonous snakebite in man. Amer. Jour.
+     Med. Sci., 237(3):277-286.
+
+PENN, G. H.
+
+     1943. Herpetological notes from Cameron Parish, Louisiana. Copeia,
+     1943(1):58-59.
+
+PERKINS, C. B.
+
+     1955. Longevity of snakes in captivity in the United States.
+     Copeia, 1955(3):262.
+
+POPE, C. H., and PERKINS, R. M.
+
+    1944. Differences in the patterns of bites of venomous and of
+    harmless snakes. Archives of Surgery, 49:331-336.
+
+RAHN, H.
+
+    1942. The reproductive cycle of the prairie rattler. Copeia,
+    1942(4):233-240.
+
+RAMSEY, L. W.
+
+    1948. Combat dance and range extension of _Agkistrodon
+    piscivorus leucostoma_. Herpetologica, 4:228.
+
+RICHMOND, M. D.
+
+     1952. Head bobbing in reptiles. Herpetologica, 8:38.
+
+ROSENFELD, S., and GLASS, S.
+
+    1940. The inhibiting effect of snake bloods upon the hemorrhagic
+    action of viper venoms on mice. Amer. Jour. Med. Sci.,
+    199:482-486.
+
+SCHMIDT, K. P.
+
+    1946. On the zoogeography of the Holarctic region. Copeia,
+    1946:144-152.
+
+SHAW, C. E.
+
+    1948. The male combat "dance" of some crotalid snakes.
+    Herpetologica, 4:137-145.
+
+    1951. Male combat in American colubrid snakes with remarks on
+    combat in other colubrid and elapid snakes. Herpetologica,
+    7(4):149-168.
+
+SMITH, H. M.
+
+    1956. Handbook of amphibians and reptiles of Kansas. 2nd
+    Edition. Univ. Kansas Mus. Nat. Hist., Misc. Publ., 9:1-356, 253
+    figs.
+
+SMITH, H. M., and BUECHNER, H. K.
+
+    1947. The influence of the Balcones Escarpment on the
+    distribution of amphibians and reptiles in Texas. Bull. Chicago
+    Acad. Sci., pp. 1-16.
+
+SMITH, P. W.
+
+    1961. The amphibians and reptiles of Illinois. Illinois Nat.
+    Hist. Survey, 28(1):1-298.
+
+SMITH, P. W., and LIST, J. C.
+
+    1955. Notes on Mississippi amphibians and reptiles. Amer. Midl.
+    Nat., 53(1):115-125.
+
+SOWDER, W. T., and GEHRES, G. W.
+
+    1963. Snakebites in Florida. Jour. Florida Med. Assn.,
+    49(12):973-976.
+
+STABLER, R. M.
+
+    1951. Some observations on two cottonmouth moccasins made during
+    12 and 14 years of captivity. Herpetologica, 7:89-92.
+
+STAHNKE, H. M.
+
+     1953. The L-C treatment of venomous bites and stings. Amer. Jour.
+     Trop. Med. and Hyg., 2(1):142-143.
+
+     1954. The L-C method of treating venomous bites and stings. Pois.
+     Anim. Res. Lab., Arizona State Coll., 28 pp.
+
+STEJNEGER, L.
+
+     1895. The poisonous snakes of North America. Smithsonian Inst., U.
+     S. Nat. Mus., 1893:337-487, pls. 1-19, figs. 1-70.
+
+STIMSON, A. C., and ENGELHARDT, T. H.
+
+     1960. The treatment of snakebite. Jour. Occ. Med., 2(4):163-168.
+
+SUTHERLAND, I. D.
+
+     1958. The "combat dance" of the timber rattlesnake. Herpetologica,
+     14(1):23-24.
+
+SWANSON, P. L.
+
+     1946. Effects of snake venoms on snakes. Copeia, 1946(4):242-249.
+
+SWAROOP, S., and GRAB, B.
+
+     1956. The snakebite mortality problem in the world. Pp. 439-466
+     _in_ Venoms (ed. Buckley, E. E., and Porges, N., Amer. Assoc. Adv.
+     Sci., Publ. No. 44).
+
+SWARTZWELDER, J. C.
+
+     1950. Snake-bite accidents in Louisiana with data on 306 cases.
+     Amer. Jour. Trop. Med., 30(4):575-589.
+
+TINKLE, D. W.
+
+     1962. Reproductive potential and cycles in female _Crotalus atrox_
+     from northwestern Texas. Copeia, 1962(2):306-313.
+
+TROWBRIDGE, A. H.
+
+     1937. Ecological observations on amphibians and reptiles collected
+     in southeastern Oklahoma during the summer of 1934. Amer. Midl.
+     Nat., 18(2):285-303.
+
+VOLSOE, H.
+
+     1944. Structure and seasonal variation of the male reproductive
+     organs in _Vipera berus_ (L.). Spolia Zool. Mus. Hauniensis V.
+     Reprint, Copenhagen, pp. 1-172.
+
+WHARTON, C. H.
+
+     1960. Birth and behavior of a brood of cottonmouths, _Agkistrodon
+     piscivorus piscivorus_, with notes on tail-luring. Herpetologica,
+     16:125-129.
+
+WILLSON, P.
+
+     1908. Snake poisoning in the United States: a study based on an
+     analysis of 740 cases. Arch. Int. Med., 1(5):516-570.
+
+WOLFF, N. O., and GITHENS, T. S.
+
+     1939a. Record venom extraction from water moccasin. Copeia,
+     1939(1):52.
+
+     1939b. Yield and toxicity of venom from snakes extracted over a
+     period of two years. Copeia, 1939(4):234.
+
+WOOD, J. T.
+
+     1954a. The distribution of poisonous snakes in Virginia. Virginia
+     Jour. Sci., 5(3):152-167, 4 maps.
+
+     1954b. A survey of 200 cases of snake-bite in Virginia. Amer. Jour.
+     Trop. Med. and Hyg., 3(5):936-943.
+
+WOOD, J. T., HOBACK, W. W., and GREEN, T. W.
+
+     1955. Treatment of snake venom poisoning with ACTH and cortisone.
+     Virginia Med. Month, 82:130-135.
+
+WRIGHT, A. H., and WRIGHT, A. A.
+
+     1957. Handbook of snakes of the United States and Canada. Comstock
+     Publ. Assoc., Cornell Univ. Press, 2:ix + 565-1106 pp.
+
+YAMAGUTI, S.
+
+     1958. Systema helminthum. Interscience Publ., Inc., New York, 3
+     vols., 5 parts, 1:xi + 1575 pp., 2:vii + 860 pp., 3:1261 pp.
+
+YERGER, R. W.
+
+     1953. Yellow bullhead preyed upon by cottonmouth moccasin. Copeia,
+     1953(2):115.
+
+     _Transmitted June 20, 1966._
+
+
+
+
+UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY
+
+
+Institutional libraries interested in publications exchange may obtain
+this series by addressing the Exchange Librarian, University of Kansas
+Library, Lawrence, Kansas. Copies for individuals, persons working in a
+particular field of study, may be obtained by addressing instead the
+Museum of Natural History, University of Kansas, Lawrence, Kansas. When
+copies are requested from the Museum, 25 cents should be included (for
+each 100 pages or part thereof) for the purpose of defraying the costs
+of wrapping and mailing. For certain longer papers an additional amount
+indicated below, toward the cost of production, is to be included.
+Materials published to date in this series are as follows.
+
+* An asterisk designates those numbers of which the Museum's
+supply (not necessarily the Library's supply) is exhausted.
+Materials published to date, in this series, are as follows:
+
+Vol. 1.
+
+     Nos. 1-26 and index. Pp. 1-638, 1946-1950.
+
+*Vol. 2.
+
+     (Complete) Mammals of Washington. By Walter W. Dalquest. Pp.
+     1-444, 140 figures in text. April 9, 1948.
+
+*Vol. 3.
+
+     Nos. 1-4 and index. Pp. 1-681. 1951.
+
+*Vol. 4.
+
+     (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41
+     plates, 31 figures in text. December 27, 1951.
+
+Vol. 5.
+
+     Nos. 1-37 and index. Pp. 1-676, 1951-1953.
+
+*Vol. 6.
+
+     (Complete) Mammals of Utah, _taxonomy and distribution_. By
+     Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables.
+     August 10, 1952.
+
+Vol. 7.
+
+     Nos. 1-15 and index. Pp. 1-651, 1952-1955.
+
+Vol. 8.
+
+     Nos. 1-10 and index. Pp. 1-675, 1954-1956.
+
+Vol. 9.
+
+     Nos. 1-23 and index. Pp. 1-690, 1955-1960.
+
+Vol. 10.
+
+     Nos. 1-10 and index. Pp. 1-626, 1956-1960.
+
+Vol. 11.
+
+     Nos. 1-10 and index. Pp. 1-703, 1958-1960.
+
+Vol. 12.
+
+     *1. Functional morphology of three bats: Eumops, Myotis,
+     Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates, 24 figures
+     in text. July 8, 1959.
+
+     *2. The ancestry of modern Amphibia: a review of the evidence.
+     By Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text. July
+     10, 1959.
+
+     3. The baculum in microtine rodents. By Sydney Anderson. Pp.
+     181-216, 49 figures in text. February 19, 1960.
+
+     *4. A new order of fishlike Amphibia from the Pennsylvanian of
+     Kansas. By Theodore H. Eaton, Jr., and Peggy Lou Stewart. Pp.
+     217-240, 12 figures in text. May 2, 1960.
+
+     5. Natural history of the Bell Vireo. By Jon C. Barlow. Pp.
+     241-296, 6 figures in text. March 7, 1962.
+
+     6. Two new pelycosaurs from the lower Permian of Oklahoma. By
+     Richard C. Fox. Pp. 297-307, 6 figures in text. May 21, 1962.
+
+     7. Vertebrates from the barrier island of Tamaulipas, Mexico.
+     By Robert K. Selander, Richard F. Johnston, B. J. Wilks, and
+     Gerald G. Raun. Pp. 309-345, plates 5-8. June 18, 1962.
+
+     8. Teeth of edestid sharks. By Theodore H. Eaton, Jr. Pp.
+     347-362, 10 figures in text. October 1, 1962.
+
+     9. Variation in the muscles and nerves of the leg in two genera
+     of grouse (Tympanuchus and Pedioecetes). By E. Bruce Holmes.
+     Pp. 363-474, 20 figures. October 25, 1962. $1.00.
+
+     10. A new genus of Pennsylvanian fish (Crossopterygii,
+     Coelacanthiformes) from Kansas. By Joan Echols. Pp. 475-501, 7
+     figures. October 25, 1963.
+
+     11. Observations on the Mississippi Kite in southwestern
+     Kansas. By Henry S. Fitch. Pp. 503-519. October 25, 1963.
+
+     12. Jaw musculature of the Mourning and White-winged doves. By
+     Robert L. Merz. Pp. 521-551, 22 figures. October 25, 1963.
+
+     13. Thoracic and coracoid arteries in two families of birds,
+     Columbidae and Hirundinidae. By Marion Anne Jenkinson. Pp.
+     553-573, 7 figures. March 2, 1964.
+
+     14. The breeding birds of Kansas. By Richard F. Johnston. Pp.
+     575-655, 10 figures. May 18, 1964. 75 cents.
+
+     15. The adductor muscles of the jaw in some primitive reptiles.
+     By Richard C. Fox. Pp. 657-680, 11 figures in text. May 18,
+     1964.
+
+     Index. Pp. 681-694.
+
+Vol. 13.
+
+     1. Five natural hybrid combinations in minnows (Cyprinidae). By
+     Frank B. Cross and W. L. Minckley. Pp. 1-18. June 1, 1960.
+
+     2. A distributional study of the amphibians of the Isthmus of
+     Tehuantepec, Mexico. By William E. Duellman. Pp. 19-72, plates
+     1-8, 3 figures in text. August 16, 1960. 50 cents.
+
+     3. A new subspecies of the slider turtle (Pseudemys scripta)
+     from Coahuila, Mexico. By John M. Legler. Pp. 73-84, plates
+     9-12, 3 figures in text. August 16, 1960.
+
+     *4. Autecology of the copperhead. By Henry S. Fitch. Pp.
+     85-288, plates 13-20, 26 figures in text. November 30, 1960.
+
+     5. Occurrence of the garter snake, Thamnophis sirtalis, in the
+     Great Plains and Rocky Mountains. By Henry S. Fitch and T. Paul
+     Maslin. Pp. 289-308, 4 figures in text. February 10, 1961.
+
+     6. Fishes of the Wakarusa River in Kansas. By James E. Deacon
+     and Artie L. Metcalf. Pp. 309-322, 1 figure in text. February
+     10, 1961.
+
+     7. Geographic variation in the North American cyprinid fish,
+     Hybopsis gracilis. By Leonard J. Olund and Frank B. Cross. Pp.
+     323-348, plates 21-24, 2 figures in text. February 10, 1961.
+
+     8. Descriptions of two species of frogs, genus Ptychohyla;
+     studies of American hylid frogs, V. By William E. Duellman. Pp.
+     349-357, plate 25, 2 figures in text. April 27, 1961.
+
+     9. Fish populations, following a drought, in the Neosho and
+     Marais des Cygnes rivers of Kansas. By James Everett Deacon.
+     Pp. 359-427, plates 26-30, 3 figures. August 11, 1961. 75
+     cents.
+
+     10. Recent soft-shelled turtles of North America (family
+     Trionychidae). By Robert G. Webb. Pp. 429-611, plates 31-54, 24
+     figures in text. February 16, 1962. $2.00.
+
+     Index. Pp. 613-624.
+
+Vol. 14.
+
+     1. Neotropical bats from western Mexico. By Sydney Anderson.
+     Pp. 1-8. October 24, 1960.
+
+     2. Geographic variation in the harvest mouse, Reithrodontomys
+     megalotis, on the central Great Plains and in adjacent regions.
+     By J. Knox Jones, Jr., and B. Mursaloglu. Pp. 9-27, 1 figure in
+     text. July 24, 1961.
+
+     3. Mammals of Mesa Verde National Pork, Colorado. By Sydney
+     Anderson. Pp. 29-67, plates 1 and 2, 3 figures in text. July
+     24, 1961.
+
+     4. A new subspecies of the black myotis (bat) from eastern
+     Mexico. By E. Raymond Hall and Ticul Alvarez. Pp. 69-72, 1
+     figure in text. December 29, 1961.
+
+     5. North American yellow bats, "Dasypterus," and a list of the
+     named kinds of the genus Lasiurus Gray. By E. Raymond Hall and
+     J. Knox Jones, Jr. Pp. 73-98, 4 figures in text. December 29,
+     1961.
+
+     6. Natural history of the brush mouse (Peromyscus boylii) in
+     Kansas with description of a new subspecies. By Charles A.
+     Long. Pp. 99-111, 1 figure in text. December 29, 1961.
+
+     7. Taxonomic status of some mice of the Peromyscus boylii group
+     in eastern Mexico, with description of a new subspecies. By
+     Ticul Alvarez. Pp. 113-120, 1 figure in text. December 29,
+     1961.
+
+     8. A new subspecies of ground squirrel (Spermophilus spilosoma)
+     from Tamaulipas, Mexico. By Ticul Alvarez. Pp. 121-124. March
+     7, 1962.
+
+     9. Taxonomic status of the free-tailed bat, Tadarida yucatanica
+     Miller. By J. Knox Jones, Jr., and Ticul Alvarez. Pp. 125-133,
+     1 figure in text. March 7, 1962.
+
+     10. A new doglike carnivore, genus Cynaretus, from the
+     Clarendonian Pliocene, of Texas. By E. Raymond Hall and Walter
+     W. Dalquest. Pp. 135-138, 2 figures in text. April 30, 1962.
+
+     11. A new subspecies of wood rat (Neotoma) from northeastern
+     Mexico. By Ticul Alvarez. Pp. 139-143, April 30, 1962.
+
+     12. Noteworthy mammals from Sinaloa, Mexico. By J. Knox Jones,
+     Jr., Ticul Alvarez, and M. Raymond Lee. Pp. 145-159. 1 figure
+     in text. May 18, 1962.
+
+     13. A new bat (Myotis) from Mexico. By E. Raymond Hall. Pp.
+     161-164, 1 figure in text. May 21, 1962.
+
+     *14. The mammals of Veracruz. By E. Raymond Hall and Walter W.
+     Dalquest. Pp. 165-362, 2 figures. May 20, 1963. $2.00.
+
+     15. The recent mammals of Tamaulipas, Mexico. By Ticul Alvarez.
+     Pp. 363-473, 5 figures in text. May 20, 1963. $1.00.
+
+     16. A new subspecies of the fruit-eating bat, Sturnira
+     ludovici, from western Mexico. By J. Knox Jones, Jr., and Gary
+     L. Phillips. Pp. 475-481, 1 figure in text. March 2, 1964.
+
+     17. Records of the fossil mammal Sinclairella, Family
+     Apatemyidae, from the Chadronian and Orellan. By William A.
+     Clemens. Pp. 483-491. 2 figures in text. March 2, 1964.
+
+     18. The mammals of Wyoming. By Charles A. Long. Pp. 493-758, 82
+     figs. July 6, 1965. $3.00.
+
+     Index. Pp. 759-784.
+
+Vol. 15.
+
+     1. The amphibians and reptiles of Michoacan, Mexico. By William
+     E. Duellman. Pp. 1-148, plates 1-6, 11 figures in text.
+     December 20, 1961. $1.50.
+
+     2. Some reptiles and amphibians from Korea. By Robert G. Webb,
+     J. Knox Jones, Jr., and George W. Byers. Pp. 149-173. January
+     31, 1962.
+
+     3. A new species of frog (Genus Tomodactylus) from western
+     Mexico. By Robert G. Webb. Pp. 175-181, 1 figure in text. March
+     7, 1962. 4. Type specimens of amphibians and reptiles in the
+     Museum of Natural History, the University of Kansas. By William
+     E. Duellman and Barbara Berg. Pp. 183-204. October 26, 1962.
+
+     5. Amphibians and Reptiles of the Rainforests of Southern El
+     Peten, Guatemala. By William E. Duellman. Pp. 205-249, plates
+     7-10, 6 figures in text. October 4, 1963.
+
+     6. A revision of snakes of the genus Conophis (Family
+     Colubridae, from Middle America). By John Wellman. Pp. 251-295,
+     9 figures in text. October 4, 1963.
+
+     7. A review of the Middle American tree frogs of the genus
+     Ptychohyla. By William E. Duellman. Pp. 297-349, plates 11-18,
+     7 figures in text. October 18, 1963. 50 cents.
+
+     *8. Natural history of the racer Coluber constrictor. By Henry
+     S. Fitch. Pp. 351-468, plates 19-22, 20 figures in text.
+     December 30, 1963. $1.00.
+
+     9. A review of the frogs of the Hyla bistincta group. By
+     William E. Duellman. Pp. 469-491, 4 figures in text. March 2,
+     1964.
+
+     10. An ecological study of the garter snake, Thamnophis
+     sirtalis. By Henry S. Fitch. Pp. 493-564, plates 23-25, 14
+     figures in text. May 17, 1965.
+
+     11. Breeding cycle in the ground skink, Lygosoma laterale. By
+     Henry S. Fitch and Harry W. Greene. Pp. 565-575, 3 figures in
+     text. May 17, 1965.
+
+     12. Amphibians and reptiles from the Yucatan Peninsula, Mexico.
+     By William E. Duellman. Pp. 577-614, 1 figure in text. June 22,
+     1965.
+
+     13. A new species of turtle, Genus Kinosternon, from Central
+     America, by John M. Legler. Pp. 615-625, pls. 26-28, 2 figures
+     in text. July 20, 1965.
+
+     14. A biogeographic account of the herpetofauna of Michoacan,
+     Mexico. By William E. Duellman. Pp. 627-709, pls. 29-36, 5
+     figures in text. December 30, 1965.
+
+     15. Amphibians and reptiles of Mesa Verde National Park,
+     Colorado. By Charles L. Douglas. Pp. 711-744, pls. 37, 38, 6
+     figures in text. March 7, 1966.
+
+     Index. Pp. 745-770.
+
+Vol. 16.
+
+     1. Distribution and taxonomy of Mammals of Nebraska. By J. Knox
+     Jones, Jr. Pp. 1-356, pls. 1-4, 82 figures in text. October 1,
+     1964. $3.50.
+
+     2. Synopsis of the lagomorphs and rodents of Korea. By J. Knox
+     Jones, Jr., and David H. Johnson. Pp. 357-407. February 12,
+     1965.
+
+     3. Mammals from Isla Cozumel, Mexico, with description of a new
+     species of harvest mouse. By J. Knox Jones, Jr., and Timothy E.
+     Lawlor. Pp. 409-419, 1 figure in text. April 13, 1965.
+
+     4. The Yucatan deer mouse, Peromyscus yucatanicus. By Timothy
+     E. Lawlor. Pp. 421-438, 2 figures in text. July 20, 1965.
+
+     5. Bats from Guatemala. By J. Knox Jones, Jr. Pp. 439-472.
+     April 18, 1966.
+
+     More numbers will appear in volume 16.
+
+Vol. 17.
+
+     1. Localities of fossil vertebrates obtained from the Niobrara
+     Formation (Cretaceous) of Kansas. By David Bardack. Pp. 1-14.
+     January 22, 1965.
+
+     2. Chorda tympani branch of the facial nerve in the middle ear
+     of tetrapods. By Richard C. Fox. Pp. 15-21, May 22, 1965.
+
+     3. Fishes of the Kansas River System in relation to
+     zoogeography of the Great Plains. By Artie L. Metcalf. Pp.
+     23-189, 4 figures in text, 51 maps. March 24, 1966.
+
+     4. Factors affecting growth and reproduction of channel
+     catfish, Ictalurus punctatus. By Bill A. Simco and Frank B.
+     Cross. Pp. 191-256, 13 figures in text. June 6, 1966.
+
+     5. A new species of fringe-limbed tree frog, genus Hyla, from
+     Darien, Panama. By William E. Duellman. Pp. 257-262, 1 figure
+     in text. June 17, 1966.
+
+     6. Taxonomic notes on some Mexican and Central American hylid
+     frogs. By William E. Duellman. Pp. 263-279. June 17, 1966.
+
+     7. Neotropical hylid frogs, genus Smilisca. By William E.
+     Duellman and Linda Trueb. Pp. 281-375, pls. 1-12, 17 figures in
+     text. July 14, 1966.
+
+     8. Birds from North Borneo. By Max C. Thompson. Pp. 377-433, 1
+     figure in text. October 27, 1966.
+
+     9. Natural history of cottonmouth moccasin, Agkistrodon
+     piscivorus (Reptilia). By Ray D. Burkett. Pp. 435-491, 7
+     figures in text. October 27, 1966.
+
+     More numbers will appear in volume 17.
+
+
+
+
+
+End of the Project Gutenberg EBook of Natural History of Cottonmouth
+Moccasin, Agkistrodon piscovorus (Reptilia), by Ray D. Burkett
+
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