Life History

Illinois snake species hibernate during the cold winter months, becoming active in spring as temperatures and day length increase. Snakes are cold-blooded and can be seen basking in the sun on logs or other objects. They are generally active during the day, but they can become nocturnal when summer temperatures rise. Snakes are solitary predators. They use their sense of smell to track prey items. Once encountered, the prey is either overpowered, constricted, or injected with venom to subdue it, and then swallowed whole. After feeding, the snake seeks out a place to hide until the prey is digested. Snakes eat a variety of prey including invertebrates, fishes, lizards, birds, rats, mice, and other small mammals. Some snakes even eat other snakes.

Although the snake's body grows throughout its life, its outer skin layer does not. The snake must shed its old skin to allow the new skin layer underneath to continue growing. At this time, the body produces a milky-blue fluid that separates the two layers of skin, which causes the clear scales over the eyes to become milky in appearance and the overall color of the snake to be drab. After a few days, the eye scales become clear and the snake begins rubbing its head on rough objects to loosen the skin. It then crawls out of the old skin. Snakes shed their skin two to four times per year depending on how much they eat. The shed skin is usually turned inside out.

A copperhead (Agkistrodon contortrix) sheddings its skin. Notice the bright pattern on the snake where the old skin has peeled away.

Snakes come together in the spring and fall for mating. Spring matings result in young born or hatched in the late summer or early fall of the year. If a female mates in fall, she will store the sperm in her body until spring. If she does not encounter a male in the spring, she can still produce young using the stored sperm. Snakes are either oviparous, ovoviviparous, or viviparous. Oviparous snakes lay leathery-shelled eggs in late May and June. The eggs are placed in moist, warm areas such as rotting logs and stumps. The young have a small egg tooth on the snout that enables them to cut through the shell. After hatching, the egg tooth falls off. Ovoviviparous and viviparous snakes retain the developing embryos in their body until late summer. Their young are born live in thin, transparent membranes from which they emerge. Snakes do not exhibit parental care for their young. Young snakes live for a few days on yolk stored in their stomach before seeking their own prey.

Recently hatched snake eggs in moist, rotting wood.

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