Snakes in Illinois

Illinois has about 40+ species of snakes, and only 4 of them are venomous. That leaves the large majority harmless and useful, keeping rodent and insect numbers down across farms, prairies, and river bottoms. Snakes are widespread here but mostly shy, and a typical sighting is a harmless species sunning on a trail or slipping into the grass.

The state stretches far enough north to south to hold very different country. The flat, glaciated north and central regions are tallgrass prairie remnants, farm fields, and scattered wetlands. The major rivers, the Mississippi, Illinois, and Ohio, carve broad floodplains and bottomland forests. Down in the far south, the Shawnee Hills bring rocky oak woodlands, bluffs, and swampy lowlands like those at the famous LaRue-Pine Hills, which packs in unusual diversity.

The 4 venomous species sort by habitat. The Eastern Copperhead lives in the rocky wooded hills of southern Illinois. The Northern Cottonmouth haunts the swamps, sloughs, and river edges of the deep south, where it is the only truly aquatic venomous snake in the state. The Timber Rattlesnake holds on in southern bluffs and bottomland forest. The Eastern Massasauga is a small, secretive wetland rattlesnake of a few scattered northern marshes, badly declined and protected. All four avoid people when they can.

Most snakes Illinoisans see are harmless. Garter snakes are everywhere, bullsnakes (a large gophersnake) hiss loudly and rattle their tails to mimic a rattlesnake and are often killed needlessly even though they are valuable rodent hunters, and watersnakes patrol ponds and rivers where they are constantly confused with cottonmouths. Fox snakes and milk snakes round out the common harmless species. Bites are uncommon and rarely fatal thanks to antivenom, and most happen when people try to handle or kill a snake. Never assume a wild snake is safe to handle, and if a bite happens, call Poison Control at 1-800-222-1222 or 911.