The Cottonmouth, scientifically known as Agkistrodon piscivorus, is a venomous snake native to the southeastern United States. It belongs to the Viperidae family and the subfamily Crotalinae, which also includes rattlesnakes and copperheads. The common names “Cottonmouth” and “Water Moccasin” are derived from the snake’s characteristic defensive display, where it opens its mouth wide, revealing the white interior that resembles cotton.
Cottonmouths are primarily found in the southeastern United States, including areas such as Florida, Georgia, Alabama, Mississippi, the Carolinas, and parts of Virginia. They can be found in nearly all freshwater habitats but are most common in cypress swamps, river floodplains, and heavily-vegetated wetlands. Cottonmouths will venture overland and are sometimes found far from permanent water. Cottonmouths often congregate around drying pools in wetlands.
In various locations, these snakes are well-adapted to less moist environments, such as palmetto thickets, pine-palmetto forests, pine woods in East Texas, pine flatwoods in Florida, eastern deciduous dune forests, dune and beach areas, riparian forests, and prairies.
Cottonmouths have a color pattern with a banded appearance. They can be beautifully marked with dark crossbands on a brown and yellow ground color or completely brown or black. Older adults are often dark and solid-colored whereas the juveniles are brightly patterned with a sulphur yellow tail tip that they wiggle to attract prey. The belly typically has dark and brownish-yellow blotches with the underside of the tail being black.
While adults tend to darken and lose their distinct banding, becoming more uniformly dark in color. Adult can measure between 2 to 4 feet in length, although larger individuals have been recorded.
This species is often confused with nonvenomous watersnakes, but watersnakes usually flee immediately if on land or in a tree, usually going underwater, whereas cottonmouths frequently stand their ground and gape to deter a predator.
Cottonmouths can be found during the day or night, but forage primarily after dark during the hotter parts of the season. Throughout much of their range, they can be found year-round, even in sunny days in the winter. Cottonmouths bask on logs, rocks, or branches at the water’s edge but seldom climb high in trees (unlike many of the nonvenomous watersnakes which commonly bask on branches several feet above the water). They employ both ambush and active foraging strategies.
They are also excellent swimmers and are often found in or near water. They can swim with most of their bodies submerged. Moreover, they are known for their defensive behavior. When stressed or threatened, Water moccasins perform a characteristic threat display that includes vibrating their tail and throwing their head back with their mouth open to display the startling white interior; they will often make a loud hiss while the neck and front part of the body is pulled into an S-shaped position. This is a defensive display, not necessarily an indication of aggression.
Other defensive responses can include flattening the body and emitting a strong, pungent secretion from the anal glands located at the base of the tail.
Cottonmouths mate in the early summer at which time male-to-male combat occurs in competition for females. Females have litters of 1-20 live young every 2-3 years. The young are large (20-33 cm) and have bright yellow tail tips.
The habit of Water moccasins snapping their jaws shut when anything touches their mouth has earned them the name “trap jaw” in some areas.
Cottonmouths are opportunistic feeders and are known to consume a variety of aquatic and terrestrial prey, including amphibians, birds lizards, snakes (including smaller cottonmouths), small turtles, baby alligators, mammals, birds, and especially fish. They are capable of consuming prey that is significantly larger than their head due to their ability to dislocate their jaws.
Cottonmouths are venomous, and their venom is hemotoxic, meaning it affects the blood and surrounding tissues. While their bites can be painful and potentially dangerous, fatalities are rare, as they usually give warning signs before striking.
Cottonmouths are ovoviviparous, meaning the females give birth to live young rather than laying eggs. The gestation period is approximately five months, and a litter may consist of 7 to 20 or more offspring.
Cottonmouths are not listed as endangered or threatened, and their populations are generally stable. However, habitat loss and human persecution pose threats to their well-being.
Identifying Characteristics From Other Species
Here are some differences you can look for in general to help distinguish cottonmouths from watersnakes:
- If the head is viewed from directly above, the eyes of cottonmouths cannot be seen, whereas the eyes of watersnakes are visible.
- Cottonmouths have vertically elliptical (cat-like) pupils whereas watersnakes have round pupils.
- Cottonmouths have a facial pit organ between the nostril and the eye, whereas watersnakes do not have this organ.
- Watersnakes usually have thin dark vertical lines on the sides of the face near the mouth, whereas the cottonmouths have no such dark lines.
- Lastly, cottonmouths typically rest with their heads elevated off the ground and tilted upwards at an angle, whereas watersnakes typically do not rest with their heads tilted upwards at an angle.
Glaudas, X., K. M. Andrews, J. D. Willson, and J. W. Gibbons. 2007. Migration patterns in a population of cottonmouths (Agkistrodon piscivorus) inhabiting an isolated wetland. Journal of Zoology 271:119-124.
Glaudas, X., and C. T. Winne. 2007. Do warning displays predict striking behavior in a viperid snake, the cottonmouth (Agkistrodon piscivorus)? Canadian Journal of Zoology 85:574-578.
Water Moccasin on The IUCN Red List site – https://www.iucnredlist.org/species/64298/12756313