Agkistrodon piscivorus: Difference between revisions
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Revision as of 10:27, 27 April 2006
| Agkistrodon piscivorus | |
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| Cottonmouth, Agkistrodon piscivorus | |
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| Genus: | Agkistrodon
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| Species: | A. piscivorus
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| Agkistrodon piscivorus | |
Agkistrodon piscivorus is a venomous pit viper species found in the United States. Also called cottonmouth and water moccasin, it is closely related to A. contortrix, otherwise known as the copperhead. Of A. piscivorus, there are currently three recognized subspecies:
- Eastern cottonmouth, Agkistrodon piscivorus piscivorus (Lacépède, 1789)
- Florida cottonmouth, Agkistrodon piscivorus conanti (Gloyd, 1969)
- Western cottonmouth, Agkistrodon piscivorus leucostoma (Troost, 1836)
Range and habitat
The eastern cottonmouth is found along the eastern coast of the United States from Virginia to Alabama. The western cottonmouth is found as far west as central Texas, through eastern Oklahoma, Missouri, as far north as southern Illinois, and east to Kentucky, Tennessee and Alabama. The Florida cottonmouth is found in the state of Florida and southern Georgia. Their ranges overlap, and intergrading of subspecies is not known.
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.
Physical description
Cottonmouths vary in size greatly, with the Florida subspecies being the largest. They average between 75 and 120cm in length, but some animals have been recorded at almost 190cm in length. They are typically dark in color, either black, dark brown, or a dark olive green, with a muddy appearance. Sometimes muted banding is present. Juveniles have a more striking appearance, with distinctive light and dark banding and a bright yellow-green tail tip. As they age, the banding and color on the tail tip fade.
Behavior
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. [1] 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. The venom of the cottonmouth is hemotoxic, causing severe necrosis near the site of the wound and potentially death of the victim if treatment is not received promptly. Treatment generally includes intravenous fluids, antibiotics, and an antivenin like CroFab. These snakes, though heavy bodied, are good climbers and they will frequently sun themselves on branches overhanging water. They are a semi-aquatic species, spending almost all their time in or very close to permanent water sources.
Juvenile cottonmouths have a behavior (shared with copperheads) of what is known as caudal luring. They use the bright color on the tip of their tail as a lure to entice prey items to approach within striking range.
Diet
Like all snakes, cottonmouths are carnivorous. They will consume a wide variety of prey including fish, small mammals, lizards, birds, small turtles, baby alligators, and even other snakes. Usually a victim is envenomated quickly with a bite and then released. If it does not succumb immediately, it is tracked by scent.
Reproduction
Cottonmouths breed yearly, in the spring. They are ovoviviparous, giving birth to 10 or so live young after a 3 month gestation. The young average around 20cm in length. There is little to no maternal care.
Status
The cottonmouth does not hold any particular conservation status, but because of its perceived aggressiveness and fear of its bite, many are killed by humans every year. Unfortunately, the far more common species of water snakes of the genus Nerodia are often mistaken for cottonmouths and many more of them are killed every year than cottonmouths.