How to Identify a Cottonmouth Snake

Cottonmouths prefer to live near water where they hunt fish, frogs and other snakes.
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Cottonmouths, also called water moccasins, are native to the southeastern United States. Their territory stretches from Texas to the Eastern Seaboard, and from the Florida Keys to the middle of Missouri. A venomous snake, the cottonmouth is often confused with non-venomous northern water snakes. While it is not advisable to get too close to a cottonmouth in order to identify it, you can discern some characteristics from a safe distance.

Body Characteristics

Cottonmouths are one of the larger snakes species, sometimes growing as long as 3 feet. Their bodies are thick and bulky compared to other snakes -- such as northern water snakes -- of the same length. Cottonmouths have tails that are short, and also thick. This snake’s body tapers at the neck, and its head is discernibly wider than its neck.

Head and Eyes

Elongated, vertical pupils and a thick head help identify a cottonmouth.
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A cottonmouth’s head is arrow-shaped, and nearly triangular when viewed from the top. However, as a means of appearing larger than they really are, some non-venomous snake species flatten their heads when danger approaches. As a result, head shape is a more difficult means of identifying cottonmouths. The snake’s head does appear more squared off at the edges, rather than rounded. Pits are visible between the eyes and nostrils, and the pupils in a cottonmouth’s eyes have a cat-like, elliptical shape. The pits are actually heat-sensitive organs that identify cottonmouths as part of the pit viper family of venomous snakes, which includes rattlesnakes and copperheads. Pits help these snakes find rodents and other warm blooded animals on which they feed.

Color Variations

A juvenile cottonmouth loses much of its bright coloration as it enters adulthood.
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Young cottonmouths are tan to brown in color with as many as 10 to 15 darker bands across their backs. Tails start out yellow in color, which newborn cottonmouths use as a lure with which to attract prey. As cottonmouths age, the tails turns more greenish, then finally black as the snake becomes an adult. Banding may be difficult to see in adult specimens as the snake’s body becomes dark brown or black as it progresses through adulthood. Adults have a white marking that extends from below each eye to the corner of the jaw. Adults also have a thin, pale white line above the eyes.

Cottonmouth Behavior

A cottonmouth opens its jaws in order to be more visible.
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Most of the time, a cottonmouth will slip away unnoticed when humans approach, often seeking water for escape. When startled or threatened, a cottonmouth’s first line of defense is not to strike, but to brandish its wide-open mouth, which is pinkish to white in color. This display is what earned the snake its name, and the cottonmouth is the only snake species that behaves this way. A cottonmouth also shakes its tail and emits a musky scent, warding predators. All snakes have the ability to swim. A cottonmouth typically does so with its head above water. Its thick body gives it more buoyancy than thinner snakes, so the cottonmouth’s entire body often barely breaks the water’s surface as it swims.

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