● Venomous · Native to the United States

Northern cottonmouth

Agkistrodon piscivorus (Lacépède, 1789)

Also called water moccasin
Data updated October 2026

Dark northern cottonmouth with faint crossbands resting on sandy, reddish ground
Fig. 1 — Adult on a sandy bank. Older snakes darken until the crossbands are hard to see.
Northern cottonmouth coiled on gravel, its broad head resting on dark banded coils
Fig. 2 — A heavy body and a broad head that is much wider than the neck.

At a glance

A heavy-bodied, dark pit viper of southern wetlands. When threatened it often holds its ground and gapes to show the white inside of its mouth. Bites are dangerous and always need emergency care.

01

Identification

Adults are dark olive, brown or nearly black, and their crossbands fade with age. The head is broad and clearly wider than the neck, with a heat-sensing pit between eye and nostril, vertical pupils and a white upper lip. The scales are heavily keeled. The belly is cream, heavily mottled with dark brown or black. Young cottonmouths are paler, with 10 to 15 distinct dark crossbands and a greenish-yellow tail tip.

  1. 01Heavy, dark body. Thick and dull-looking, with bands that are faint or hidden in older adults.
  2. 02Broad head, white lip. The head is much wider than the neck; the upper lip is white.
  3. 03White-mouth display. When threatened it may coil, vibrate its tail and gape to show the white or pinkish lining of its mouth.

Commonly confused with

Copperhead vs cottonmouth: how to tell them apart →

In the field, harmless watersnakes are mistaken for cottonmouths far more often than any of these.

02

Size

01 ft2 ft3 ft4 ft Typical adult · about 40 in (102 cm)

Most adults measure 24 to 48 inches (61–122 cm). Exceptional snakes pass 60 inches (152 cm), and the species has been recorded at 75 inches. Males grow larger than females. Newborns are about 7 to 10 inches (18–25 cm) long.

03

Range & habitat

Cottonmouth in shallow grassy water, gaping to show the pale lining of its mouth
Fig. 3 — Shallow, grassy water is typical habitat. This snake is gaping to show the pale lining of its mouth.

Northern cottonmouths range across the southeastern United States, from southeastern Virginia west through the Gulf states to eastern Texas, Oklahoma and Arkansas, and north up the Mississippi Valley into southern Missouri and the southern tip of Illinois. Cottonmouths in Florida are now treated as a separate species, the Florida cottonmouth.

They live in cypress swamps, river floodplains, sloughs, oxbow lakes, drainage ditches and slow, heavily vegetated waters. In the Missouri Ozarks they also use cool, spring-fed, rocky creeks. They move into nearby uplands at night, during droughts and when dispersing.

State guides: Texas · Oklahoma

04

Diet & predators

Cottonmouths eat almost any animal they can overpower. Fish and frogs are common prey, along with salamanders, other snakes, lizards, small turtles, birds and small mammals. They also scavenge dead animals. Most hunting is done from ambush.

Feeds on

  • Fish
  • Frogs and salamanders
  • Snakes and small turtles
  • Birds, rodents and carrion

Preyed on by

  • Kingsnakes
  • People, through habitat loss, roads and killing

05

Behavior & seasons

In hot weather cottonmouths hunt mainly at dusk and at night. They tend to rely on camouflage or a defensive display rather than fleeing. Despite their reputation, research shows they rarely bite unless stepped on or picked up.

In Missouri they are active from late April through October and often spend the winter in rock crevices along limestone bluffs. When are snakes active in Texas?

06

Reproduction

Cottonmouths give birth to live young in late summer and early fall, mostly in August and September. Litters hold 2 to 15 young, with an average of six or seven in Missouri. Females there appear to breed only every other year. Young become mature in two to three years.

07

Conservation

The species is listed as Least Concern. Local populations have declined because of wetland loss, road mortality and deliberate killing.

08 — Bite safety

If someone is bitten

Cottonmouth bites are rarely fatal, but every bite needs medical care. Call 911 or go to the nearest emergency department. For guidance, call Poison Control at 1-800-222-1222. If a pet is bitten, take it to a veterinarian right away.

This page does not give first-aid or treatment instructions. Read our safety disclaimer.

Keep reading

Sources

Data updated October 2026 · How we build these pages