How to Identify the Cottonmouth (Identification Guide)

Key identifying features

The Cottonmouth, also known as the water moccasin, is identified by its heavy-bodied build, dark, often nearly black adult coloration, and its habit of gaping open its mouth to reveal a strikingly pale, cotton-white interior when threatened, from which its common name derives. Its close association with freshwater habitats also aids identification.

Coloration & pattern

Juveniles show a more distinct pattern of brown or reddish-brown crossbands on a lighter tan or olive background, along with a bright yellow-green tail tip used to lure prey. As adults mature, the pattern typically darkens considerably, often becoming a nearly uniform dark brown, olive, or black, with the banding pattern becoming faint or barely visible except under close inspection. The belly can be mottled with dark and light blotches.

Head, eyes & scales

The head is large, blocky, and distinctly wider than the neck, with a somewhat flattened crown typical of pit vipers. A dark stripe often runs through the eye. Eyes have vertically elliptical pupils, though this can be hard to see in very dark individuals. Body scales are keeled, giving a dull, rough texture rather than a glossy sheen.

Size & body shape

This is a heavy-bodied, thick snake with a stout midsection tapering to a shorter tail than many non-venomous water snakes. It swims with much of its body riding on the surface of the water, rather than mostly submerged.

Range & habitat where you'll see it

Found throughout the southeastern United States, the Cottonmouth is closely tied to wetlands, swamps, slow-moving streams, ponds, and lake margins. It is often seen basking near or in the water and is capable of both aquatic and terrestrial movement.

How to tell it apart from look-alikes

Its thick body, blocky head, and dark adult coloration distinguish it from slender, non-venomous water snakes in the same wetland habitats, which tend to have narrower heads and more visible banding retained into adulthood. The distinctive open-mouthed white gape display, when observed, is a strong confirming field mark not shared by similar-looking water snakes.