There are four species of venomous snakes found in Illinois—copperhead (Agkistrodon contortrix), cottonmouth (Agkistrodon piscivorus), timber rattlesnake (Crotalus horridus) and massasauga (Sistrurus catenatus). In Illinois, the timber rattlesnake is listed as a threatened species and the massasauga is listed as endangered. The cottonmouth is found only in the very southern tip of the state. The copperhead is found in the southern two-thirds of the state.
Venomous snakes use their venom to kill the birds and small animals that they eat. While snake venom may cause tissue or nerve damage, a venomous snake bite is usually not fatal to humans when proper medical treatment is received. The risk of being bitten by a venomous snake in Illinois is very low since all four species are nonaggressive towards people.
Check out the IDNR’s Wild About Illinois Snakes! website to learn more about these four species.
The Prairie Research Institute’s Illinois Natural History Survey provides a species distribution map and more natural history information about the copperhead, cottonmouth, timber rattlesnake and massasauga.