Non-Venomous Snakes in Illinois

Illinois has large areas of natural habitat that offer a home to an array of wildlife. The varied habitats are well suited for 27 species of non-venomous snakes. The native species are varied in size and appearance, ranging from a few inches to over 8 feet in length. Some of the state's snakes are also considered endangered or threatened.

  1. Large Snakes

    • A large number of Illinois non-venomous snakes are large, often growing to over 4 feet in length. One of the largest is the gopher snake, which grows to 70 inches. The gray rat snake is slightly smaller at 68 inches, with the western mud and eastern racer being smaller still at 59 inches on average. The diamondback water snake and the plain bellied water snake grow to around 55 inches. The rest of the large native species grow to just over 4 feet; they are the western fox, the prairie king and the common king snakes.

    Medium-Sized Snakes

    • Most of the state's species tend to be medium-sized, between 2 and 4 feet in length. The milk snake and northern water snake grow to just under 4 feet on average. The eastern hog-nosed snake, rough green snake, smooth green snake, grahams crayfish snake, queen snake, western ribbon snake, plains garter snake and the common garter snake all grow to around 3 feet in length.

    Small Snakes

    • Illinois is home to several small snake species that do not grow more than 2 feet long. The eastern worm snake, red-bellied snake, lined snake and eastern smooth snakes all grow to be just over a foot. The ring-necked snake and Dekay's brown snake both grow to between 17 and 18 inches in length. All six species tend to have slender bodies.

    Endangered and Threatened Snakes

    • Of the state's native species, eight are considered endangered or threatened. Illinois' largest snake, the coachwhip, grows to 102 inches and is listed as endangered. The southern water snake and eastern ribbon snake are also both protected as endangered in the state. Illinois' smallest snake, the 8-inch long flat-headed snake, is also a threatened species. Also among the state's threatened species are Kirtland's snake, great plains rat snake, western hog-nosed snake and the Mississippi green water snake.