The eastern massasauga (Sistrurus catenatus) is found in scattered populations throughout Illinois, including Washington County in southern Illinois and Cook County in the northeastern region of the state. This snake may be identified by its heavy body, dark brown splotches on its skin and stripes on its head. Eastern massasaugas are rattlesnakes. As adults, this snake species may grow up to 3 1/2 feet in length. Varying habitats for eastern massasaugas include woodlands, prairies and bogs. An eastern massasauga's diet consists of small birds, reptiles, amphibians and mammals, particularly rodents.
In Illinois, the timbler rattlesnake (Crotalus horridus) appears in the southern and south central regions of the state, including Illinois' Shawnee Hills region. This snake is one of the largest venomous snake in the state, reaching lengths of 4 1/2 to 5 feet when it reaches adulthood. Timbler rattlesnakes live in several habitats, such as deciduous and coniferous forests, rocky cliffs and near aquatic areas. The dorsal region of this snake features dark arrow-style designs on its skin; the arrow-style markings run from the snake's head to tail. This snake is threatened in Illinois due to agricultural development and habitat loss.
The range of the western cottonmouth (Agkistrodon piscivorus leucostoma) extends from Central Texas up to southern Illinois. This snake primarily lives in aquatic habitats such as rivers, ponds, lakes and bogs; however, western cottonmouths may live in drier environments if necessary. When swimming, the western cottonmouth swims with most of its body touching the water's surface as opposed to nonvenomous water snakes, whose bodies are usually underwater. This snake receives its name from the skin inside its mouth, which is a bright white. When alarmed, the western cottonmouth will open its mouth before it strikes. This snake grows up to 3 feet long.
Copperheads (Agkistrodon contortrix) are named after the copper coloration on their skin. Brown hourglass-shaped crossbands accompany the snake's copper-based skin. In Illinois, copperheads are found in the state's southeastern counties, particularly in the Shawnee Hills and near the Mississippi River. This snake species usually lives in the woods; during the summer, though, copperheads may be seen in grassland habitats. As adults, these snakes grow over 3 feet in length. Copperheads may be found in animal burrows and in abandoned buildings such as warehouses and barns.