Agkistrodon piscivorus is a venomous pit viper species found in the eastern United States. It is a close
relative of the copperhead, A. contortrix. Three subspecies are currently recognized, including the typical
form described here.
This is the largest species of the genus Agkistrodon. Adults commonly exceed 80 cm (roughly 2 ft. 8 in.) in length, with males growing larger than females. They have a heavy body with a moderately long tail. Occasionally, individuals may exceed 180 cm in length, especially in the eastern part of the range.
Found in the eastern United States from extreme southeastern Virginia, south through the Florida peninsula and west to Arkansas, southeastern Kansas, eastern and southern Oklahoma, and eastern and central Texas. A few records exist of the species being found along the Rio Grande in Texas, but these are thought to represent disjunct populations, now possibly extirpated. The type locality given is 'Carolina,' although Schmidt (1953) proposed that this be restricted to the area around Charleston, South Carolina.
Cottonmouths are rarely found far from a permanent water source, such as a slow moving stream, edge of a lake, pond, swamp, or even brackish tidal estuaries. Throughout much of their range, they are found in open flatwood pine forests or bald cypress swamps. They are abundant in abandoned rice ditches.
Within their range, cottonmouths have a reputation as being aggressive snakes. However, in tests designed to measure the suite of behavioral responses by free-ranging cottonmouths to encounters with humans, 51 percent of the test subjects tried to escape and 78 percent used threat displays or other defensive tactics. Only when the snakes were picked up with a mechanical hand were they likely to bite.
In addition, many of the snakes that did bite did not inject venom. Such a 'dry' bite could also be another, more serious threat display. Unlike most snakes, including the copperhead, when startled the cottonmouth often will stand its ground and open its mouth ('gape' or 'smile') to warn predators to stay away. That behavior is many times seen as aggressive, but if left alone they will leave.
These snakes are semi-aquatic, spending almost all their time close to permanent water sources. They swim with much of their bodies floating above the surface distinguishing them from water snakes, which tend to swim mostly below the surface, sometimes with their heads protruding.
They take a wide variety of prey. Usually a victim is envenomated quickly with a bite and then released. If the prey does not succumb immediately, it is tracked by scent. Like all pit vipers, the cottonmouth has pits on the sides of its nose that sense bodyheat of warm blooded animals in the form of infrared light, thus its hunting ability is not impaired at night. The name 'cottonmouth' is earned by the snake´s tendency to open its mouth widely, displaying white tissue inside as a warning gesture.
Read more: 3 other pages about cottonmouth:
Mangroveswamp with Cottonmouth snake, Mangroveterrarium for cottonmouth, Newcomer: Florida cottonmouth - Agkistrodon piscivorus ,