Venomous Snakes Of Illinois

There are 40 snake species native to Illinois, and they are found in all types of habitat from woodlands and prairies to wetlands and urban areas.  Of these, four species are venomous.  A venomous snake is one that uses a chemical toxin to kill its prey.  This internally developed chemical is delivered through a pair of hollow fangs in the upper jaw of the mouth.  When the snake opens its mouth, the fangs drop down and venom is injected into the prey as the snake bites.  The snake will then release the prey, waiting for the venom to kill it before swallowing the prey whole.  Juveniles will inject less venom, but with the same potency as adults.

Venomous snakes in Illinois are all pit vipers, a sub-family of the Viperidae family of snakes.  The pit, a large opening between the eye and the nostril, just above the upper lip, can detect heat given off by warm-blooded prey species.  Their elliptically-shaped eyes is another characteristic that helps to identify venomous snakes.

Illinois venomous snakes are non-aggressive in nature, but will bite if cornered, harassed, or stepped on.  Bites are usually not fatal in humans, but they can be quite painful, often resulting in swelling and possible infection.  Vomiting, nausea, and tissue or nerve damage may also result.  Anyone that is bitten should seek immediate medical attention.

The Eastern Copperhead, Agkistrodon contortrix, lives in the southern third of Illinois on wooded hillsides, river bluffs with sandstone or limestone outcroppings, and along forest edges.  During the hot summer months, they may also feed on the abundant rodent populations in meadows or near abandoned buildings.  The copperhead is  about four feet in length and has a light brown back with one to two dozen reddish-brown colored hourglass-shaped markings along the back.  The top of their head is a brighter red-brown.

The Northern Cottonmouth, Agkistrodon piscivorus, resides in far southern parts of Illinois, living in swamps, sloughs, and oxbow lakes.  At five feet in length, this heavy-bodied snake is a uniform charcoal or dark olive color, with dark crossbands and a tan to gray belly.  When disturbed, its response is to face its attacker and open its mouth widely, displaying the bright white interior, earning the name of cottonmouth.

Timber rattlesnakes, Crotalus horridus, live in both southern and northern areas along the Mississippi River and Illinois River valleys.  Usually found in heavy timber with rock outcrops or bluffs, this snake, up to six feet long, is marked by two dozen black crossbars down a gray-green-yellow back.  Its belly is light-colored with dark edges, and it shows a dark strip behind each eye.  Timber rattlesnakes will hunt in any areas where there is a large rodent population.  They are listed as threatened since we have seen sharp declines in the populations in recent years.

The Massasauga Rattlesnake, Sistrurus catenatus, is found in small numbers scattered across the state, mainly in prairie wetlands and river floodplains.  Listed as endangered in the United States, it has become quite rare in Illinois with only a couple sightings annually for the past several years.  Massasaugas are about two feet in length, with a gray to light brown back and 30-40 dark, bow-tie shaped markings.  Four to seven darker rings cover the tail.  Their main prey is small rodents.

Venomous snakes have small ranges, staying close to home for hunting and mating.  Their main predators include humans, birds of prey, and other snakes.  Many have been killed by people with an unfounded fear of these creatures.  Although they play a major role in controlling rodent populations, there has been little concern shown over loss of habitat due to draining of wetlands and other urban development.  Plan a visit to the Jurica-Suchy Nature Museum or a nature center near you to learn more about these mysterious, yet wonderous species.