All the American copperheads, cottonmouths, and rattlesnakes are members of the family Viperidae. Fossil records suggest that this large family of snakes, which includes species as diverse as the giant vipers of Africa (puff adders, gaboon vipers, and rhinoceros vipers) to the comparatively tiny pygmy rattlesnakes of southeastern North America, originated on the Asian continent.All New World viperids have the bilateral heat-sensitive pit organs and are therefore members of the subfamily Crotalinae.The common origin for the New World pit viper species complex may account for the reported variable degrees of cross-reactivity of antivenoms with the venoms of genera and species that were not used in its production.

The viperid envenomation apparatus consists of a pair of long, hollow, movable maxillary fangs (solenoglyphous dentition).Because fang movement and the ejection of venom are both operated by skeletal muscle, both are under voluntary control.In a given bite incident, a snake may or may not use the fangs, and even if it uses the fangs it may not inject venom. Handling, restraining, or agitating snakes by repeated attempts to capture or kill the animals are all factors that can lead to serious envenomation.Therefore, venomous snakes encountered in the field are best given a wide berth and left alone.

Cottonmouths

13 Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. Map 1 13. Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. , 15. Tennant A. A Field Guide to Texas Snakes. , 16. Price A.H. Poisonous Snakes of Texas. , 17. Campbell J.A.

Lamar W.W. Venomous Reptiles of the Western Hemisphere. , 18. Gibbons W.

Dorcas M. Snakes of the Southeast. , 20. Conant R. A Field Guide to the Reptiles and Amphibians of Eastern and Central North America. The distribution range of the cottonmouth (Agkistrodon piscivorus) within the United States. This map is an approximated summation of the distribution range data for all 3 cottonmouth subspecies and includes data from several field guides and the monograph on the Agkistrodon species complex. When one thinks about snakes indigenous to the hurricane-prone areas in the eastern United States, the cottonmouth or water moccasin (Agkistrodon piscivorus) is probably the first species to come to mind. The cottonmouth is a large, dark, heavy-bodied snake that ranges throughout most of the southeastern and south-central United States ( Map 1 ). Cottonmouths are the largest snakes in the New World Agkistrodon species complex and are the only members of the group that are semiaquatic.Three distinct subspecies are recognized: the eastern cottonmouth, the Florida cottonmouth, and the western cottonmouth.

Figure 1 Illustrations of the 3 cottonmouth subspecies in comparison with a potential mimic, the southern water snake (Nerodia fasciata). A. The eastern cottonmouth (Agkistrodon p piscivorus) (photo by John Willson at the Savannah River Ecology Laboratory [SREL]). B. The Florida cottonmouth (Agkistrodon p conanti) (Alachua County, FL) (photo by Edward Wozniak). C. Western cottonmouth (Agkistrodon p leucostoma) (Polk County, TX) (photo by Michael Smith). D. Southern water snake (N fasciata) (harmless) (photo by John Willson at the SREL). Note the distinct 2-tone coloration, the spadelike shape of the head, the lateral position of the eyes, the vertically elliptical pupils, the cheek stripes, and the loreal pits of the cottonmouths and compare each with the water snake. Whereas the head of an alarmed water snake is distinctly triangular, it has an arrowhead-like shape in comparison with that of the cottonmouth (inset picture in Figure 1D), which retains its spadelike shape even in an enraged individual. Many species of water snakes have large protruding eyes with distinctly round pupils that are medial to the lateral margins of the widened head, unlike any of the 3 cottonmouth species. All these features are helpful in differentiating cottonmouths from water snakes in the field. The medium-sized Florida cottonmouth shown in Figure 1B has taken refuge on a limb protruding from floodwater. Even small amounts of leafy vegetation can effectively conceal snakes. Contact with vegetation protruding from or hanging over floodwater should be avoided. The ground color of A piscivorus varies from brown to olive to black, and the dorsum of all 3 subspecies is marked with 10 to 17 broad, dark brown, black-edged crossbands with pale centers that often bear 1 or more dark round spots in the centrolateral aspect. All 3 subspecies undergo ontogenetic cutaneous melanization with anteriograde darkening of the body, beginning with the tail. In yearling to adult specimens, this phenomenon typically causes the dorsal pattern to fade and the background color to darken on the caudal aspect of the body, giving the snake a characteristic “2-tone” pattern of body coloration ( Figure 1 ). Learning to recognize this pattern can be helpful in quickly distinguishing most cottonmouths from nonvenomous water snakes in the field. With older adult snakes, however, the advanced degree of melanization can obscure the dorsal pattern over much of the body, causing some individuals to appear almost entirely black. At the other end of the age spectrum, neonatal cottonmouths are often reddish brown with bright yellow or greenish tails and are so strongly patterned that they are frequently mistaken for copperheads.

15 Tennant A. A Field Guide to Texas Snakes. 15 Tennant A. A Field Guide to Texas Snakes. 15 Tennant A. A Field Guide to Texas Snakes. The cottonmouth is probably the most frequently misidentified snake in North America, largely because of its frequent confusion with the more common harmless natricine water snakes (Nerodia spp) that are superficially similar in appearance. In addition to the previously described pattern and coloration characteristics, the spade-shaped head bearing supraocular scales that overhang the eyes when viewed from directly above, their gaping behavior, and their habit of vibrating the tail when disturbed are all features that can be helpful in quickly differentiating cottonmouths from harmless natricine water snakes in the field. Other less obvious but distinctive physical characteristics that typify the species include a crown of 9 plates on the dorsal head, a “flattened” or “squared off” rostral profile, the presence of bilateral loreal pit organs, elliptical pupils, and third upper labial scales that extend from the lip to the ventral margins of the eyes.Many species of nonvenomous water snakes (Nerodia spp) are capable of flattening and widening their head into a distinctly triangular, arrowhead-like shape when alarmed. The sudden change in head shape from a normally narrow profile to the arrowhead-like conformation when alarmed, the medial position of the eyes relative to the lateral head margins, the round pupils, the pointed snout profile, the vertical striping on the labial scale edges ( Figure 1D ), the lack of the overall 2-tone coloration, and the failure to gape and vibrate the tail are all features that may also be helpful in differentiating water snakes from cottonmouths. When undisturbed in water, cottonmouths usually swim with their whole body floating buoyantly and their head held well above the water surface.In contrast to this, natricine water snakes and ribbon snakes typically swim with most of their body underwater with just their head resting on the surface.When threatened or disturbed, however, cottonmouths and water snakes are both capable of diving and, despite urban legends, can and will bite underwater if stepped on or otherwise restrained.

15 Tennant A. A Field Guide to Texas Snakes. 29 Gibbons W.

Dorcas M. Defensive behavior of cottonmouths (Agkistrodon piscivorus) toward humans. 29 Gibbons W.

Dorcas M. Defensive behavior of cottonmouths (Agkistrodon piscivorus) toward humans. 8 Russell F.E. Snake Venom Poisoning. , 9 Lawrence W.T.

Giannopoulos A.

Hansen A. Pitviper bites: rational management in locales in which copperheads and cottonmouths predominate. 4 Green L, Ulferts A. Several health risks rise along with storm watchers. St Petersburg Times OnLine. Available at: http://sptimes.com/2004/09/05/weather/several health risks.shtml. Accessed October 16, 2005. 30 Murdock R.T.

White Jr, G.L.

Pedersen D.M.

DeFaller J.M.

Snyder C.C. Prevention and emergency field management of venomous snakebites during military exercises. The open-mouth threat display of the cottonmouth (gaping behavior) along with the continued circulation of popular and scary fictitious urban legends concerning their perceived aggressive behavior and venom potency have resulted in the cottonmouth having an undeserved bad reputation.Behavioral studies have demonstrated that in most instances cottonmouths that are challenged or threatened by humans will either attempt to escape or rely heavily on threat displays and other defensive tactics.Only when grabbed, restrained, or stepped on will cottonmouths regularly use their fangs and venom defensively.Because of this and their preference for habitats that humans typically find undesirable, cottonmouths usually account for only a small percentage of the annually reported venomous snakebites in the United States.In disaster-stricken areas harboring dense populations of cottonmouths, however, the incidence of bites inflicted by this species may be markedly increased.In flooded areas, bites to the upper half of the body have been documented in troops who had accidentally brushed into heavily foliated vegetation sticking up out of floodwater on which displaced cottonmouths had taken refuge.Therefore, emergency-response personnel are well advised to become familiar with the distribution, identification, biology, and behavioral characteristics of the cottonmouths.

13 Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. All 3 of the cottonmouth subspecies are highly adaptable pit vipers capable of surviving in and around cities, towns, and rural residences. In some areas, cottonmouths are the most common venomous serpents to show up in towns, buildings, and other domestic areas during disasters involving floods. Cottonmouths will readily enter brackish or salt water, and dense populations of this species can be found on many of the barrier islands along the Atlantic and Gulf coasts.A description of each subspecies is provided below.

Eastern cottonmouth 13 Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. The eastern cottonmouth (A p piscivorus) inhabits the southeastern quadrant of the United States, extending from the Great Dismal Swamp in extreme southeastern Virginia southward along the Atlantic Coast to the level of central Georgia and westward through Alabama into the northeastern corner of Mississippi.The eastern cottonmouth is one of the most colorful cottonmouth subspecies and is readily distinguished from the Florida race, Agkistrodon p conanti, by the lack of the dark vertical markings on the rostrum and from the western race, Agkistrodon p leucostoma, by its coloration and the presence of conspicuous dark cheek stripes on the lateral head ( Figure 1A ). The body profile of the eastern cottonmouth is often somewhat more triangular than the other 2 subspecies, most notably on the anterior body.

Florida cottonmouth 13 Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. 13 Gloyd H.K.

Conant R. Snakes of the Agkistrodon Complex: A Monograph Review. The Florida cottonmouth is the largest member of the A piscivorus complex. The head of A p conanti is conspicuously marked with vertical stripes on the rostrum and mental regions that create a distinctive “handlebar mustache–like” marking on the rostrum when viewed from the front ( Figure 1B ). Like their eastern cousins, Florida cottonmouths typically have prominent bilateral dark cheek stripes that are conspicuously bordered by light areas above and below.This pattern of head markings can be so striking that untrained people accustomed to seeing the less colorful western race sometimes have trouble identifying the Florida subspecies as a cottonmouth (E.J.W., personal observation). The Florida cottonmouth ranges from the southeastern extreme of South Carolina through coastal and southern Georgia, southward throughout the state of Florida, and westward along the Gulf Coast to the eastern face of Mobile Bay in Alabama.