Agkistrodon piscivorus
cottonmouth
(Also: water moccasin)

Cottonmouths, Agkistrodon piscivorus , are found in the United States ranging from as far north as the James River in Virginia to the western edge of Missouri, and as far south as the Florida Keys and the western part of Texas. They are found in parts of North Carolina, South Carolina, Georgia, Kentucky, Illinois, Indiana, Tennessee and all of Louisiana, Alabama, Mississippi and Arkansas. (Mitchell, 1994; Roth and Noble, 2005; Wilson, 1995; Zaidan III, Kreider, and Beaupre, 2003)

Cottonmouths prefer wetlands but are also found on land in vegetation and under logs and branches. Because cottonmouths are semiaquatic, they are most commonly found in moist habitats in close proximity to water. Cottonmouths can be found in bodies of water including bays, salt marshes, lakes, creeks, ditches, and even on river bottoms. (Mitchell, 1994; Wilson, 1995)

Cottonmouths have a maximum total length of 1.8 m and a maximum mass of 1700 grams. Males are typically longer, heavier, and have a greater number of subcaudal scales (enlarged scales on tail) than females. The heads of adults are large, spade-shaped, and brown, black, or olive on top or laterally. They also have brown patches on their chins. Adults are black, brown, and olive and have black crossbands down the length of their bodies. The crossbands are usually darker on the outside of the band with a lighter center and are dumbbell shaped. The closer to the tail, the darker the crossbands get until they are completely black at the end of the tail. Juvenile cottonmouths have a similar pattern, but have a yellow tip on the end of their tails, brighter overall color, and more distinct crossbands. The mouth is bright white inside, which gives them their common name. (Means, 2004; Mitchell, 1994)

After copulation, female cottonmouths retain the eggs, which develop inside of her for 5 months, after which they give birth to live young. The sex of the young is determined through genetics, not the environment. These snakes exhibit determinate growth. (Ford, Brischoux, and Lancaster, 2004)

In each clutch, on average, just 2 to 3 young make it to adulthood. Cottonmouth young suffer high predation rates. Little information has been documented on the lifespan of Agkistrodon piscivorous in captivity or in the wild, however, the oldest cottonmouth known lived to 24.5 years old. (de Magalhaes, Costa, and Toussaint, 2005a; Mitchell, 1994)

Cottonmouths are solitary and do not wander far from their home range. Adults will not go far from sources of water (no more than 500 m) but juveniles will venture a little farther. Although cottonmouths are generally solitary, a temporary hierarchy among males is established during the mating season when they "dance" to attract a mate. Cottonmouths are aggressive snakes and bite when disturbed or provoked. They first give warning signs by shaking their tail back and forth, making a rustling noise, elevating their heads off the ground a few inches, and coiling up while exposing their open white mouth. As a defense mechanism or in a situation when they are threatened they will emit a foul-smelling musk as well. Cottonmouths are venomous and can bite while on land or in water. Cottonmouths are typically nocturnal. (Gibbons and Dorcas, 2002; Mitchell, 1994; Roth and Noble, 2005)

Home Range

Cottonmouth home range size averages 1.06 ha, typically including a water source, such as a river or lake. The size of a cottonmouth's home range tends to increase with the size of the snake and varies with gender. Males typically have significantly larger home ranges than both gravid and non-gravid females. (Mitchell, 1994; Roth and Noble, 2005; Wilson, 1995)

Cottonmouths use vision, touch, smell, and sound. They use their eyes to locate prey and their senses of hearing and touch to better perceive their surroundings. Their strongest sense is the sense of smell, in which they use their tongue to "taste" the air. This is used to analyze what is in the air around them. Cottonmouths also use a gland to spray a foul-smelling musk up to 1.5 m away to warn potential predators. (Means, 2004; Mitchell, 1994)

Cottonmouths are carnivores, eating primarily mammals and fish. Cottonmouths catch their food by striking, biting, and releasing venom into the prey. They also hold the prey in their coils until it is no longer struggling. Cottonmouths then open their mouths wider than the normal size by detaching the jaw bones, making it easier to swallow the prey. Other prey taken includes frogs, turtles, snakes, eggs, insects, carrion, and birds. Common prey species include southern leopard frogs (Rana sphenocephala), catfish (Ictalurus), bass (Micropterus), juvenile black rat snakes (Elaphe obsoleta), young snapping turtles (g.Chelydra serpentina), and least shrews (Cryptotis parva). (Lillywhite and McCleary, 2008; Mitchell, 1991; Mitchell, 1994; Wilson, 1995)

The main predators of mature cottonmouths are humans Homo sapiens, mostly indirectly via habitat destruction. There are many predators of young cottonmouths. Known predators of juveniles are raccoons (Procyon lotor), longnose gar (Lepisosteus osseus), dogs (Canis lupus familiaris), cats (Felis catus), hawks (Buteo and Accipiter), eagles (Haliaeetus), egrets (Ardea and Egretta), largemouth bass (Micropterus salmoides), and snapping turtles (Chelydra serpentina). Their anti-predator adaptations include hiding, flattening themselves closer and using their cryptic coloration to blend in with the environment, coiling and rapidly shaking their tail in vegetation to make a rattlesnake-like sound, opening their mouth wide to present their very white mouths, swimming away, and using a gland that sprays a foul-smelling chemical to deter the predator. (Gibbons and Dorcas, 2002; Mitchell, 1994)

Cottonmouths are important predators of shrews, other small mammals, snakes, fish, amphibians, and turtles. Young cottonmouths are also prey to larger predators. Cottonmouths are carriers of many types of parasites. Dasymetra is a digenetic trematode genus that occurs in cottonmouths and are usually located in the esophagus or mouth. Ochetosoma ancistrodontis and Ochetosoma aniarun are digenetic trematodes that are usually found in the mouth and esophagus, especially in the tissue folds. Another parasite found in cottonmouths is Pneumatophilus foliaformis, which is a digenetic trematode located in the lungs and trachea. Proteocephalus marenzelleri and Proteocephalus perspicua are cestodes found in the distal and proximal one-third of the small intestines of the cottonmouth. Kiricephalus coarctatus and Porocephalus crotali are pentastomids that can be found in the lungs of cottonmouths. These parasites can cause infections in the lungs of cottonmouths but cause no inflammation in the lungs. (Detterline, Jacob, and Wilhelm, 1984)

As a venomous snake, cottonmouths have the ability to bite, poison, and potentially kill humans. Because cottonmouths are found in water and on land, and because they are common along the shores of ponds, lakes, and rivers, encounters between humans and cottonmouths are frequent. However, cottonmouths are generally secretive and are not aggressive, so bites are rare. Furthermore, cottonmouths, and other pitvipers, that bite defensively, typically inject less venom than they would if they were trying to kill a prey item. (Gibbons and Dorcas, 1998; Gibbons and Dorcas, 2002; Mitchell, 1994)

By keeping populations of small animals under control, cottonmouths may indirectly limit the effects of pest species. Humans benefit directly from cottonmouths because snake skin is sometimes used as a kind of leather. (Mitchell, 1991; Mitchell, 1994)

Agkistrodon piscivorus is listed as a species of "least concern" by the IUCN Red List. Cottonmouths are not an endangered or threatened species and populations seems to be stable throughout their range.