Skip to main content

Archive - July 2016

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.

Snake Species in Illinois

Family Colubridae - The family Colubridae is the largest family of snakes in the world. Because of the great number of species found in this category, it is difficult to find characteristics that are common to all of its members. Three features that they have in common are no pelvic girdle, no functioning left lung and the head covered by large scales. All of the colubrid snakes in Illinois lay eggs and are harmless to humans.
     scarletsnake (Cemophora coccinea)
     North American racer (Coluber constrictor)
     coachwhip (Coluber flagellum) [state endangered]
     prairie kingsnake (Lampropeltis calligaster)
     eastern kingsnake (Lampropeltis getula)
     eastern milksnake (Lampropeltis triangulum)
     rough greensnake (Opheodrys aestivus)
     smooth greensnake (Opheodrys vernalis)
     Great Plains ratsnake (Pantherophis emoryi) [state endangered]
     western foxsnake (Pantherophis ramspotti)
     gray ratsnake (Pantherophis spiloides)
     eastern foxsnake (Pantherophis vulpinus)
     gophersnake (Pituophis catenifer
     flat-headed snake (Tantilla gracilis) [state threatened]

Family CrotalidaeThese are the venomous snakes including the rattlesnakes, copperhead and cottonmouth that are found in Illinois. These “pit vipers” have a pit on each side of the head that detects infrared radiation to help them locate warm-blooded prey at night. They also have a pair of fangs in the front of the mouth, a triangular-shaped head and an elliptical pupil in the eye. They give birth to live young.
     eastern copperhead (Agkistrodon contortrix)
     northern cottonmouth (Agkistrodon piscivorus)
     timber rattlesnake (Crotalus horridus) [state threatened]
     eastern massasauga (Sistrurus catenatus) [state and federally endangered]

Family Dipsadidae - The members of this family are generally small snakes that have teeth in the back of the jaw that are used to transfer venom into their prey. They lay eggs and are harmless to humans.
     common wormsnake (Carphophis amoenus)
     western wormsnake (Carphophis vermis)
     ring-necked snake (Diadophis punctatus)
     red-bellied mudsnake (Farancia abacura)
     plains hog-nosed snake (Heterodon nasicus) [state threatened]
     eastern hog-nosed snake (Heterodon platirhinos)

Life History

​Illinois snake species hibernate during the winter months, becoming active in spring as temperatures and day length increase. Snakes are cold blooded (having a body temperature that varies with that of the environment) and can be seen basking in the sun on logs or other objects to warm their body. They are generally active during the day, but can become nocturnal when summer temperatures rise. Snakes are solitary predators. They use their sense of smell to track prey items. Depending on the species, the prey is either overpowered, constricted (method used by some snakes to kill prey by coiling tightly around the prey item to prevent it from breathing) 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 items including invertebrates, amphibians, 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 fluid that separates the two layers of skin, causing 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.

Snakes come together in the spring and fall for mating. Spring mating results 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 oviparous, ovoviviparous or viviparous.

oviparous [oh-vip-er-uh s] - animals producing eggs that hatch outside the body of the female

ovoviviparous [oh-voh-vie-vip-er-uh s] - species in which the eggs develop and hatch inside the female’s body

viviparous [vie-vip-er-uh s] - species in which the young are born live after developing completely within the female’s body

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.

Venomous Snakes

​​Venom is a poisonous secretion transmitted by a bite or a sting. In snakes, it is used to subdue prey. It is delivered through a pair of hollow fangs in the front, upper mouth that fold up when the mouth is closed and drop into place when the snake bites. The fangs are shed and replaced periodically. Venomous snakes strike, inject venom and then pull away. They find and eat the prey after it dies. Illinois’ venomous snakes produce venom that affects the blood of the prey. Juvenile snakes have venom equal in potency to that of the adult, but they produce lesser amounts. Four native Illinois snake species are venomous: the copperhead, cottonmouth, timber rattlesnake and massasauga. Illinois’ venomous snakes are pit vipers, having a large opening, or pit, on each side of the head between the eye and nostril. It is used to detect heat emitted by potential warm blooded prey. Besides the pit, venomous snakes can be recognized by the elliptical pupil in the eye. With the exception of the timber rattlesnake, the tip of the tail is bright yellow in all juvenile Illinois venomous snakes.

Venomous snakes tend to be restricted to specific habitats. Copperheads occur in the southern one-third of Illinois, south of Route 16, and in the lower Illinois River valley. They prefer upland forests or river bluffs with limestone or sandstone outcroppings. Cottonmouths live in swamps and wet bottomlands in southern Illinois, south of Route 13. Timber rattlesnakes may be found in the southern one fourth of the state (south of Interstate 64), in the lower Illinois River valley, in the Mississippi River valley and in a few other locations. These snakes prefer heavy timber with rock outcrops and bluffs. Massasaugas live in scattered locations within the counties of Madison, Clinton, Piatt, Knox, Warren, Will, Cook and Lake. Their habitats are prairie wetlands and river floodplains.

While venomous snakes are not aggressive and tend to bite people only when stepped on, picked up or cornered, their bite is a serious matter. Even freshly killed snakes can bite. These snakes should be avoided and precautions taken (wear leather boots, do not reach under rocks or logs, do not step over rocks or logs, look around before you sit) if you are entering an area possibly inhabited by venomous snakes. Although usually not deadly, the bite is painful and can cause swelling, nausea and the risk of infection. If you are bitten, go to a hospital for treatment immediately.


Eleven Illinois snake species are listed as either state endangered or state threatened (as of 2016). Several of these species are at the edge of their geographic range in Illinois, occurring in only a few counties and having never been present in large numbers. Kirtland’s snake, the massasauga and timber rattlesnake, however, are sharply declining over a large area of the United States.

Habitat alteration and loss are major factors in the declining populations of snake species. Many people do not consider snakes beneficial and are not concerned about destroying the forests, grasslands, swamps and sloughs where snakes live. Another factor is the illegal trade of reptiles in Illinois. There are several laws designed to protect all native Illinois snake species. However, selling reptiles can be profitable and is tempting to some people even though it is illegal. Killing of snakes because of human misinformation, lack of information and irrational fears has also affected populations. Habitat preservation, law enforcement and education are the keys to conserving Illinois snakes.

Snake Facts

​The smallest snake in Illinois is the flat-headed snake. The longest Illinois specimen measures eight inches.

The largest Illinois snake is the gopher snake, with the Illinois record length at seven feet, two inches.

A snake can swallow prey that is three times larger than the size of its own head.

Snakes are very efficient rodent controllers. Large and medium-sized snakes can eat up to nine pounds of rats and mice per year.

Snake scales and rattlesnake rattles are made of keratin, a hard protein also found in the hair, fingernails and hooves of other animals.

Snakes have four rows of teeth in the top of the mouth and two rows on the bottom of the mouth.

Rattlesnakes add a new segment at the base of the rattle each time the snake sheds its skin. Old segments at the tip may disintegrate or break off.

Kingsnakes are immune to the venom of copperheads, cottonmouths and rattlesnakes.

When threatened, a hog-nosed snake spreads its head and neck, somewhat like a cobra would, then rolls over and plays dead if it continues to be disturbed.

Podcast and Resources