Cottonmouth Snake (Agkistrodon piscivorus)

The cottonmouth snake is one of the most recognizable—and misidentified—snakes of the southeastern United States. Also called a water moccasin, this heavy-bodied pit viper inhabits wetlands, bayous, ponds, marshes, streams, and other aquatic habitats.

Nearly every dark snake seen near water is accused of being a cottonmouth. In reality, several harmless Texas watersnakes share the same habitats and are far more commonly encountered.

Learning the differences protects people and prevents harmless snakes from being killed unnecessarily.

Quick Facts

Common Name	Cottonmouth and water moccasin
Scientific name	Agkistrodon piscivorus
Family	Viperidae
Type	Venomous semiaquatic pit viper
Average Length	Approximately 3–3½ feet (91–107 cm)
Color	Brown, olive, gray, dark brown, or nearly black
Distinctive feature	White interior of the mouth
Diet	Fish, frogs, reptiles, birds, small mammals, and carrion
Habitat	Swamps, bayous, marshes, ponds, rivers, and slow waterways
Activity	Primarily nocturnal or crepuscular
Reproduction	Viviparous (Gives birth to live young)
Conservation Status	G5 (Globally secure), and S5 (secure within Texas)

Description

Cottonmouths are thick, muscular snakes with broad heads and strongly keeled scales. Their colors vary widely.

Young cottonmouths are usually tan or brown with bold, dark crossbands. The pattern may contain darker spots and irregular edges that create a pixelated or jagged appearance.

Adults often become progressively darker with age. Large individuals may appear olive, dark brown, or almost solid black, although faint bands can remain visible in good light.

A dark stripe typically extends through the eye toward the corner of the mouth. Pale cream or white markings may border the lower jaw.

How to Identify a Cottonmouth

Look for several features together:

• Thick, heavy body
• Dark brown, olive, gray, or black coloration
• Broad, dark crossbands
• Dark facial stripe through the eye
• Pale markings along the jaw
• Blocky head with a distinct neck
• Keeled scales
• Yellow or green tail tip on juveniles
• Bright white mouth lining when displayed

The open-mouth display is a warning, not an invitation to inspect the snake more closely. A cottonmouth may never show its mouth, so the white interior should not be your only identification feature.

Why Is It Called a Cottonmouth?

When threatened, the snake may coil, raise its head, hiss, and open its mouth. The bright white lining resembles a piece of cotton and contrasts sharply with the snake’s dark body.

This behavior is meant to make a predator stop and reconsider. It gives the snake another defensive option before biting.

A cottonmouth may also vibrate its tail, flatten its body, release musk, or retreat toward nearby cover.

Cottonmouth or Watersnake?

Harmless watersnakes are regularly mistaken for cottonmouths. Both groups may have dark bands, thick bodies, keeled scales, and defensive attitudes.

Useful differences include:

• Cottonmouths often have a dark stripe through the eye.
• The eyes are partly shielded from above by raised scales.
• Pale jaw markings may be visible.
• Young cottonmouths have yellow or green tail tips.
• Cottonmouth bands often have irregular, jagged edges.
• Watersnakes frequently have vertical bars along the lips.

None of these requires approaching the snake. Use a camera zoom or binoculars and remain well outside striking distance.

How a snake holds its body while swimming is not reliable enough to make a confident identification by itself.

Diet

Cottonmouths are opportunistic predators with a remarkably broad diet. They eat fish, frogs, salamanders, turtles, small alligators, snakes, birds, mammals, insects, and carrion.

Fish and amphibians are important prey, but cottonmouths are not limited to aquatic animals. They may hunt along shorelines, beneath logs, among wetland vegetation, or on dry ground near water.

Young cottonmouths use their brightly colored tail tips as lures. The tail resembles a small worm and draws frogs or lizards within reach.

Habitat and Range

Cottonmouths occur throughout much of the southeastern United States. Their range extends from southeastern Virginia through the Carolinas and Georgia, south into Florida, and west across Alabama, Mississippi, Louisiana, and eastern Texas. Inland populations also occur in portions of Arkansas, Oklahoma, Missouri, Tennessee, Kentucky, and southern Illinois. They occur around:

• Swamps
• Bayous
• Coastal marshes
• Slow rivers
• Ponds
• Lakes
• Creek margins
• Floodplain forests
• Drainage ditches
• Wet pastures

They are strongly associated with water but may travel across dry ground, especially when moving between wetlands or searching for shelter.

Along the Texas Gulf Coast, cottonmouth habitat often overlaps with alligators, watersnakes, frogs, turtles, wading birds, and aquatic mammals.

Behavior

Cottonmouths have a reputation for chasing people, but research does not support the idea that they hunt or pursue humans.

In a field study of defensive behavior, most cottonmouths attempted to escape or relied on warning displays. Biting was more likely only after severe physical provocation.

A snake moving toward someone may be attempting to reach water, vegetation, a burrow, or another hiding place located in that direction. Give it room and move away slowly.

Defensive does not mean harmless. A cornered or handled cottonmouth can strike quickly and should never be approached.

Venom and Bite Safety

Cottonmouth venom can cause severe pain, swelling, bruising, blistering, tissue damage, and systemic illness. Every suspected bite is a medical emergency.

Call 911, remain as still as possible, remove rings or tight items before swelling begins, and allow someone else to transport the patient. Do not apply ice, cut the wound, use suction, or attempt to capture the snake.

Venomous Snakes Guide and Identification

Life History and Reproduction

Cottonmouths may mate during spring or autumn. During the breeding season, males sometimes compete for females through ritualized combat. They raise the front portions of their bodies, twist together, and press against one another until one male retreats.

Females are viviparous, which means they give birth to live young rather than laying eggs. Birth usually occurs during late summer or early autumn. Although litter size varies, females commonly produce several young at a time.

Newborn cottonmouths resemble smaller, more brightly patterned versions of the adults. In addition, each young snake has a yellow or green tail tip that it uses to lure frogs, lizards, and other small prey.

Some females may remain near their newborns for a short time. However, the young quickly become independent and must hunt and defend themselves soon after birth.

Conservation Status

Cottonmouths remain widespread throughout much of the southeastern United States wherever suitable wetland habitat survives. Therefore, the species is not currently listed as threatened or endangered at the federal level.

Even so, local populations may decline when wetlands are drained, polluted, or divided by development. Road mortality also affects cottonmouths as they travel between ponds, marshes, floodplains, and other aquatic habitats. In addition, many are deliberately killed because of fear or misidentification.

Despite their reputation, cottonmouths play an important ecological role. As predators, they help control populations of fish, frogs, rodents, and other small animals. At the same time, they provide food for birds of prey, larger snakes, mammals, and alligators. Consequently, protecting wetland habitats also supports the cottonmouth and the many other species that share its ecosystem.

Fun Facts

• Cottonmouths are among North America’s few semiaquatic vipers.
• The scientific name piscivorus refers to fish eating.
• Juveniles are much more brightly patterned than many adults.
• Young cottonmouths use colorful tails to lure prey.
• Cottonmouths may eat carrion as well as live prey.
• They can bite while in water, although most encounters do not result in bites.
• Harmless watersnakes are commonly mistaken for cottonmouths.
• The white-mouth display is a defensive warning.

Frequently Asked Questions

Will a cottonmouth chase you?

Cottonmouths do not hunt or chase people. A frightened snake may move toward nearby shelter, even when that shelter happens to be in the observer’s direction.

Is every dark snake near water a cottonmouth?

No. Broad-banded watersnakes, diamond-backed watersnakes, plain-bellied watersnakes, and other harmless species are common in the same habitats.

Do cottonmouths always show their white mouths?

No. Some flee, freeze, flatten their bodies, or remain motionless. The open-mouth display is only one possible response.

Can cottonmouths climb trees?

They can climb low limbs, roots, fallen trees, and rough surfaces. However, snakes commonly seen resting on branches above water are often harmless watersnakes.

Can cottonmouths live away from water?

Yes. They may travel across dry land or shelter in wooded areas, fields, and structures near wetlands.

Are young cottonmouths venomous?

Yes. They are venomous from birth and should never be handled.

Naturalist’s Note

A dark snake disappearing from a muddy bank can produce an instant cottonmouth verdict. Often, the observer saw only a body, a splash, and a few seconds of movement.

Wetlands are crowded neighborhoods. Cottonmouths share them with several watersnakes that are equally comfortable swimming, basking, and defending themselves when frightened.

Pause before assigning a name. A photograph taken from a respectful distance may reveal barred lips, facial stripes, crossbands, or other clues. Even when identification remains uncertain, the safest response is the same: give the snake space and let it continue on its way.

Similar Species

• Broad-banded watersnake: A harmless, heavy-bodied snake common around Gulf Coast waterways.
• Diamond-backed watersnake: Large and thick with a chainlike diamond pattern and strongly barred lips.
• Plain-bellied watersnake: Often dark above with a plain yellow, orange, or reddish underside.
• Copperhead: Usually lighter with clear hourglass-shaped bands and less association with open water.
• Mudsnake: A glossy dark snake with red or pink bars on the belly; secretive and nonvenomous.