20 / OutdoorIllinois March 2010

Is it poisonous or venomous?There is a difference.

Apoisonous plant or animalcauses harm if touched orconsumed. Venomousorganisms inject a toxin tosubdue their prey, as is

done by the hollow fangs of the fourspecies of pit vipers found in Illinois—copperhead (Agkistrodon contortrix),cottonmouth (Agkistrodon piscivorus),timber rattlesnake (Crotalus horridus)and eastern massasauga (Sistrurus cate-natus). The pit is a large openingbetween the eye and nostril used todetect heat emitted by their prey. Ven-omous snakes in Illinois also have anelliptical pupil.

Venomous snakes are not aggressiveand tend to bite people only whenstepped on, picked up or cornered.

Learn to identify, and avoid thesesnakes when possible.

Copperheads have a light tan orrusty ground color and 10-20 darkerbrown, hourglass-shaped crossbandsthat are narrow on the back and widenon the sides. Locally abundant in wood-ed, rocky hillsides in the southern one-third of Illinois, south of Route 16, andin the lower Illinois River valley, cop-perheads prefer upland forests or bluffswith limestone or sandstone outcrop-pings.

The stout-bodied cottonmouth isrelatively abundant in swamps, sloughsand wet bottomlands in extreme south-ern Illinois, south of Illinois Route 13.Young snakes have 12-18 dark cross-bands on a brown or dark-brown back,and a wide, dark stripe from the nosethrough the eye and upper lip. Olderadults are dark olive or black. Whenthreatened, cottonmouths open theirmouth, displaying a whitish lining.

Found in heavily timbered areaswith river bluffs and rock outcrops inthe southern one-fourth of the state,the lower Illinois and Mississippi rivervalleys and a few other locations is thetimber rattlesnake. These stout-bod-ied snakes are gray to light yellow togreenish-white, with 20-25 black,jagged bands, and sometimes a rustystripe down the back. A dark stripe isbehind each eye. Timber rattlesnakesare listed as threatened in Illinois.

Prairie wetlands, wet oldfields andriver floodplains in Madison, Clinton,Piatt, Knox, Warren, Will, Cook andLake counties provide habitat for thestate-endangered Eastern massas-auga. The smallest venomous snake inIllinois, massasaugas are light brown togray and have 29-40 light-edged brownor black spots down their back andthree rows of smaller blotches alongeach side. A small rattle is at the end ofthe tail.

Venomous Snakes

eastern massasauga (Sistrurus catenatus)eastern massasauga (Sistrurus catenatus)timber rattlesnake (Crotalus horridus)timber rattlesnake (Crotalus horridus)

cottonmouth (Agkistrodon piscivorus)cottonmouth (Agkistrodon piscivorus)copperhead (Agkistrodon contortrix)copperhead (Agkistrodon contortrix)