Northern Cottonmouth

Agkistrodon piscivorus


Image of a northern cottonmouth
The cottonmouth is a semi-aquatic, venomous snake named for the cotton-white lining of its mouth, which it opens widely when alarmed.
Jim Rathert
Other Common Name
Water Moccasin

Viperidae (venomous snakes) in the order Squamata (lizards and snakes)


The name “cottonmouth” is from the whitish lining of its mouth. When alarmed, it opens its mouth widely, showing the cotton-white lining. The body is black with little or no pattern, or dark brown with darker bands on the back. The belly is dark brown or black. Young cottonmouths are patterned something like a copperhead and usually have a yellowish-green tail. Like all venomous snakes in Missouri, cottonmouths have a hole between the nostril and the eye, and the pupils are vertical, like a cat’s.

Similar species: There are several species of nonvenomous semiaquatic snakes found in Missouri. These harmless watersnakes vastly outnumber the much-feared cottonmouths. All are protected by law.


Length: 30–42 inches.


Video of a western cottonmouth in the wild.

Northern Cottonmouth-20181028-1313.JPG

A dark brown snake with black bands is half-submerged in shallow water. It's mouth is open, showing a cotton-white lining.
Northern Cottonmouth near Poplar Bluff
Habitat and conservation

This species lives in two distinctly different habitats; in southeastern Missouri, they live in swamps and oxbow lakes, and in the southern Ozarks, they live in cool, spring-fed rocky creeks and river sloughs. The cottonmouth is a dangerously venomous species that can deliver a fatal bite. Various harmless snakes, especially watersnakes, are often misidentified as cottonmouths and needlessly killed. Learn to identify them and refrain from destroying snakes. All Missouri snakes are protected by law.


The cottonmouth is a semiaquatic predator. It is primarily a fish-eater, but it also eats frogs, other snakes, lizards, and rodents. The young have a greenish-yellow tail and use it like a lure to attract frogs, lizards, and other prey.

Northern Cottonmouth Distribution Map
Distribution in Missouri

Southeastern corner; a spotty distribution throughout the Ozark Region. None occur north of the Missouri River in our state.


Has a limited range in Missouri. Missouri is the northwestern limit of this species. Low winter temperatures limit its distribution.

Life cycle

Active from late April through early October. They bask in the sun in spring and autumn but are mainly nocturnal. In autumn, they often move from their swamps to bluffs to overwinter in ledges, often with other species of snakes. Courtship and mating are most prevalent in the spring. Cottonmouths give birth in August and September; litters average 6 or 7 young. Females probably give birth only every other year.

Human connections

People naturally fear venomous snakes, yet these animals also intrigue us and are deeply significant for human cultures all over the world. Learning about them helps us to coexist with these creatures that remain a vital part of the natural order.

Ecosystem connections

Snakes are an integral part of the wildlife community and play vital roles in their respective ecosystems. They are also protected by Missouri's Wildlife Code. While snakes can evoke irrational fear in those who encounter them, it is still unlawful to kill, harm, or harass them.