It is important for those who spend time in Missouri’s outdoors to learn to identify venomous snakes. Use these photos, descriptions and maps to familiarize yourself with the size, color and distribution of these snakes. Several species of harmless snakes (hognose, garter and water snakes) spread their head and neck when alarmed, which may cause the head to appear triangle-shaped. Consequently, this characteristic is not reliable for distinguishing venomous snakes from harmless ones.
All of Missouri’s venomous snakes are pit vipers, which means they have an opening on each side of the head, called a sensory pit. A pair of hollow fangs are located on the front of the upper jaw. In daylight these snakes have eyes with vertical pupils—like a cat—while all harmless snakes have round pupils. This characteristic is not reliable for identification at night. Even the underside of the tail is helpful in distinguishing the two types of snakes: our venomous species have a single row of scales, while harmless snakes have two rows of scales.
Osage Copperhead
Agkistrodon contortrix phaeogaster
This is our most common venomous snake. Color varies from grayish-brown to
pinkish-tan, with hourglass-shaped crossbands of dark gray, brown or reddish-brown.
The head may have some pink or orange color, hence the name “copperhead.”
The tail may be yellow or greenish-yellow, especially in young specimens, and
the belly usually is a dusky mixture of gray, tan and black. Length averages
from 24 to 36 inches (61-91 cm). Copperheads make their homes on rocky hillsides
and along the edges of forests. They also spend time among trees and in brush
along prairie streams. Copperheads are often found near abandoned farm buildings.
Copperheads will vibrate their tail when alarmed. There is no record of a human
death caused by a copperhead bite in this state, but medical treatment for such
bites is necessary. Copperheads eat mice, lizards, frogs and sometimes small
snakes.
Missouri Distribution: The Osage copperhead is found over the northern two-thirds of the state and is replaced by the southern copperhead—a subspecies—in the southern third of the state (shown in green on map).
Western Cottonmouth
Agkistrodon piscivorus leucostoma
Local Name: water moccasin
The name “cottonmouth” is derived from the white-colored lining
of this snake’s mouth. When alarmed, it opens its mouth widely, showing
the cotton-white lining. General body color is black with little or no pattern
or dark brown with darker crossbands on the back. The belly is dark brown or
black. Length averages from 30 to 42 inches (76-107 cm). Young cottonmouths
are superficially patterned like a copperhead and usually have a yellowish-green
tail. This species lives in two distinctly different habitats; in south-eastern
Missouri, they live in swamps and oxbow lakes, and in the southern Ozarks, they
live in rocky streams and river sloughs. The cottonmouth is a dangerously venomous
species that can deliver a fatal bite. It is semi-aquatic, primarily a fish-eater
but also eats frogs, other snakes, lizards and rodents. Various harmless snakes
often are misidentified as cottonmouths and needlessly killed.
Missouri Distribution: Southeastern corner and a spotty distribution throughout the Ozark Region.
Timber Rattlesnake
Crotalus horridus
This is Missouri’s largest venomous snake. Generally tan or yellowish-tan,
the timber rattlesnake has markings along the back which are dark brown and
change from blotches on the neck to bands near the tail. Often, a dark line
extends from the eye along the angle of the jaw, and there is a rust-colored
stripe down the back. It has a large rattle at the end of its tail. Length averages
36 to 60 inches (91-152 cm). This rattlesnake lives on rocky, wooded hillsides.
In Missouri, it tends to congregate in selected south-facing rocky areas where
it overwinters. Timber rattlesnakes eat a variety of rodents and also small
rabbits. It is dangerously venomous, but there are few cases of rattlesnake
bites in this state.
Missouri Distribution: Statewide.
Eastern Massasauga Rattlesnake
Sistrurus catenatus catenatus
Local Name: swamp rattler
This snake is gray to dark gray with numerous brown or gray-brown blotches.
The belly is dark gray or black, and there is usually a dark brown band extending
backward from the eye onto the side of the neck. The end of the tail has a small
rattle. Length averages from 18 to 30 inches (46-76 cm). This snake lives in
marshy areas or wet prairies and may take shelter in burrows of crayfish or
other animals. Massasaugas have become rare in Missouri because of habitat destruction
and are on the state’s Rare and Endangered Species list. Human deaths
caused by its bite are rare, but tests show that the massasuga’s venom
is highly toxic, so it must be respected and classified as dangerous. Massasaugas
eat mice, shrews, frogs and lizards.
Missouri Distribution: This species is found in scattered populations in the northern half of Missouri.
Western Pygmy Rattlesnake
Sistrurus miliarius streckeri
Local Name: ground rattler
This is one of the smallest species of rattlesnakes in North America. General
color is light grayish-brown, with a row of small, dark brown spots on the back
and similar spots on each side. Most specimens also have a rust-colored stripe
down the back. The belly is usually gray. The pygmy rattlesnake has a thin tail
and a tiny rattle. Length averages from 15 to 20 inches (38-51 cm). This species
lives under rocks on cedar glades and is so secretive that few people encounter
it. The sound of the vibrating rattle is a faint buzz like the sound of a grasshopper.
Food includes small lizards, snakes, frogs and mice. Although the bite of this
species is not fatal, a bite victim should seek immediate medical attention.
The pygmy rattlesnake should be respected and left alone.
Missouri Distribution: Counties bordering Arkansas and the eastern Missouri Ozarks.
Content revision: 2004/05/20
