Thirty-nine species of snakes inhabit Illinois, living in forests, grasslands, marshes, swamps, ponds, lakes, streams, rivers and sloughs. Some species are quite common, while others are very rare. These reptiles are solitary predators that eat a variety of prey.
Snakes, like all reptiles, have a scale-covered body. The dry scales reduce moisture loss through the skin. Depending upon the species, scales are either keeled (raised ridge) or smooth. Snakes do not have eyelids. Each eye is covered with a clear, hard scale. The snake’s tongue is used in the sense of smell. By flicking its forked tongue out of the mouth, a snake can pick up chemical particles from the air around it. When the tongue is pulled back into the mouth, the fork tips are placed into the Jacobson’s organ, located in the front part of the roof of the mouth. The snake detects odors by analyzing the particles with its nervous system. The sense of smell is important to this animal for recognizing prey, enemies and a mate. Snakes have teeth that are curved toward the back of the mouth so that prey items cannot easily escape once they are in the mouth. The lower jaws are movable which allows the snake to take in large food items.
Snakes do not have legs, yet they can move quickly and easily. Their flexible movements are the result of their reduced skeletal system, composed of a skull, many vertebrae and many ribs. The skeletal and muscular systems along with the platelike scutes on the belly work together to allow a snake to move swiftly, pushing off of surface irregularities in the places it crawls.
The male snake has paired reproductive organs, called hemipenes, stored in the base of the tail, one part along each side. They are used to transfer sperm to the female. Only one hemipenis is used at any time, and the one used depends on which side of the female’s body the male snake is crawling along.