Cottonmouth Confusion

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Published on: Jun. 2, 2004

Last revision: Nov. 16, 2010

Cottonmouth snake in defensive posture

"Uh-Oh! I think I just saw a snake in the water!"

Those words have needlessly ended a lot of fishing trips. Some people are so spooked by water snakes that the mere sight of one puts an abrupt end to any outing. Some uninformed outdoorsmen even go out of their way to kill them.

Many people falsely believe that any snake seen in or near the water is a water moccasin, also known as a cottonmouth. Along with cottonmouths, there are seven different species of non-venomous, semi-aquatic snakes found in our state and in most of Missouri. These non-venomous water snakes vastly outnumber the much feared cottonmouths, and they are the ones that usually frighten anglers and other stream lovers.

Most of Missouri's non-venomous snakes that are mistaken for cottonmouths belong to a single genus, Nerodia. Missouri is home to five species within this genus, and they share some interesting characteristics. All five primarily eat fish and amphibians. They don't have venom, but they put up quite a bluff when cornered. When threatened, they flatten their head and neck in order to look larger. They also bite and are known to release a pungent musk from a gland near their tail.

Admittedly, it can be difficult to identify a snake when you unexpectedly encounter one in the wild, especially if it is in the water. The following snakes are the ones most often mistaken for cottonmouths.

Northern Water Snake

(Nerodia sipedon)

The northern water snake is the most common semiaquatic, non-venomous snake in Missouri. Ranging statewide, it often shares habitat with cottonmouth snakes and is the snake most often misidentified as a cottonmouth. This snake is brown to orange. The bands crossing its back are darker than those on a cottonmouth. Its belly is cream colored with irregularly spaced half-moons or spots of orange or red.

On a warm spring day it wouldn't be unusual to see half a dozen northern water snakes while you're out fishing. You might even see one with its head protruding from the water like a periscope.

Diamond-Backed Water Snake

(Nerodia rhombifer)

This is the largest species of water snake found in our state. The Missouri record is 51 inches long. The nonvenomous, diamond-backed water snake ranges across large sections of Missouri, but it is not found in the Ozarks or extreme northern Missouri. It prefers the swamps, oxbow lakes and marshes common in the Bootheel

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