Four native Illinois snake species are venomous: the
copperhead (Agkistrodon contortrix), the cottonmouth (Agkistrodon
piscivorus), the timber rattlesnake (Crotalus horridus), and the
eastern massasauga (Sistrurus catenatus). Venom is a toxin for subduing
prey. It is delivered through a pair of hollow fangs in the front, upper mouth
that fold up when the mouth is closed and drop into place when the snake bites.
The fangs are shed and replaced periodically. Venomous snakes strike, inject
venom, then pull away. They find and eat the prey after it dies. Illinois' venomous
snakes produce venom that affects the blood of the prey. Juvenile snakes have
venom equal in potency to that of the adult, but they produce lesser amounts.
venomous snakes are pit vipers, having a large opening, or "pit," on each side
of the head between the eye and nostril. It is used to detect heat emitted by
potential warm-blooded prey. Besides the pit, venomous snakes can be recognized
by the elliptical pupil in the eye. With the exception of the timber rattlesnake,
the tip of the tail is bright yellow in all juvenile Illinois venomous snakes.
of a timber rattlesnake (Crotalus horridus) shows the characteristics
of a pit viper. Note the elliptical pupil in the eye and the heat-sensing pit,
which is seen just above the upper lip, between the eye and the nostril.
Venomous snakes tend to be restricted to specific habitats.
Copperheads occur in the southern one-third of Illinois, south of Route 16,
and in the lower Illinois River valley. They prefer upland forests or river
bluffs with limestone or sandstone outcroppings. Cottonmouths live in swamps
and wet bottomlands in southern Illinois, south of Route 13. Timber rattlesnakes
may be found in the southern one-fourth of the state (south of Interstate 64),
in the lower Illinois River valley, in the Mississippi River valley and in a
few other locations. These snakes prefer heavy
timber with rock outcrops and bluffs. Eastern massasaugas live in scattered
locations within the counties of Madison, Clinton, Piatt, Knox, Warren, Will,
Cook, and Lake. Their habitats are prairie wetlands and river floodplains.
While venomous snakes are not aggressive and tend to
bite people only when stepped on, picked up, or cornered, their bite is a serious
matter. Even freshly killed snakes can bite. These snakes should be avoided
and precautions taken (wear leather boots, do not reach under rocks or logs,
do not step over rocks or logs, look around before you sit) if you are entering
an area possibly inhabited by venomous snakes. Although usually not deadly,
the bite is painful and can cause swelling, nausea, and the risk of infection.
If you are bitten, go to a hospital for treatment immediately.
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