“What kinds of venomous snakes can you find in Illinois?”
This question is extremely common. Everyone wants to know if any dangerous snakes live near them and what they look like!
Believe it or not, you can find FOUR types of venomous snakes in Illinois. But please don’t live in fear, thinking that you are going to be bitten. In general, snakes try to avoid any contact or interaction with people. As long as you leave them alone, you shouldn’t have any trouble!
Did you know that snakes are considered venomous, NOT poisonous? If you eat something that makes you sick, then it’s considered “poisonous.” If an animal, like a snake, delivers its toxins when it bites, then it’s considered “venomous.”
*If you come across any of these species, PLEASE DO NOT DISTURB! Venomous snakes are dangerous animals and should be left alone. The more you agitate them, the more likely you could get bitten. DO NOT RELY ON THIS ARTICLE to correctly identify a snake that has recently bitten you. If you have recently been bitten, GO DIRECTLY to the nearest hospital to get help and to determine if the snake is venomous.*
4 Venomous Snakes That Live in Illinois:
#1. Eastern Copperhead
- Agkistrodon contortrix
- Adults reach lengths between 20 and 37 inches.
- Stout body and broad head and elliptical pupils.
- Coloration varies from pale tan to pinkish-tan with darker, splotchy, hourglass-shaped bands, which are darker at the edges and thinner towards the center of the back.
Look for these venomous snakes in southern Illinois in deciduous forests and mixed woodlands, often near rocky outcroppings. However, they may also be seen in swampy areas, coniferous forests, and near river habitats. You’re most likely to see them active during the day in the spring and fall when the weather is cooler. During the middle of summer, Eastern Copperheads are often nocturnal.
Eastern Copperhead Range Map
Credit: Virginia Herpetological Society
This species is an ambush hunter, meaning that it selects a suitable site and waits to surprise its prey. In addition, copperheads are considered “pit vipers,” which means they have a heat-sensing organ located between their eyes. This adaptation helps these venomous snakes locate and judge the size of their prey by being able to sense infrared!
Bites from these venomous snakes are rarely fatal in Illinois.
The venom they produce has relatively low potency. In addition, copperheads also frequently employ false strikes, dry bites, and warning bites. Dry bites contain no venom, and warning bites have a relatively small amount of venom.
These snakes primarily feed on small rodents, frogs, birds, and large insects, such as cicadas. After the initial bite, they will wait for the venom to take effect before consuming their prey whole.
When threatened, Eastern Copperheads use a “freeze” defense. Their excellent camouflage coloration allows them to blend into the leaf litter and soil. However, they may also vibrate their tails in the leaves when approached to produce a buzzing sound. This noise may serve to warn predators, similar to a rattlesnake, or divert a predator’s attack to their tail.
#2. Northern Cottonmouth
- Agkistrodon piscivorus
- Adults range from 26 to 35 inches in length. Females are typically smaller than males.
- Most individuals are dark gray to black with a broad head, heat-sensing pits between the eyes and nostrils, elliptical pupils, and a blunt snout.
- Some individuals have a brown, gray, tan, or blackish coloration.
Cottonmouths are the ONLY aquatic venomous snake in Illinois.
Be on the lookout for them near bodies of water, including swamps, marshes, ponds, and slow-moving streams and rivers, as well as semi-permanent water sources like flooded fields and drainage ditches. But they aren’t limited to just aquatic habitats and can also be found in palmetto thickets, pine forests, dune areas, and prairies.
Northern Cottonmouth Range Map
Credit: Virginia Herpetological Society
Since they are typically near water, the bulk of their diet is made up of fish and frogs. But they are opportunistic and will also eat small mammals, birds, turtles, small alligators, and other snakes.
These venomous snakes, which are also commonly called Water Moccasins, Black Moccasins, or Gapers, have several defensive tactics. They often vibrate their tail in the leaf litter, pull their heads up and back, and then open their mouth to hiss and expose a white interior. This particular display is what earned them the name “cottonmouth.”
Luckily, receiving a bite from a Northern Cottonmouth is rare. But when it does happen, it is very serious. Their venom destroys tissue and is more toxic than a copperhead but not as severe as a rattlesnake. It is rare to die from their bite, but it does cause swelling and bruising and can leave scars.
#3. Timber Rattlesnake
- Crotalus horridus
- Adults typically range from 30 to 60 inches in length.
- Coloration is variable, and generally ranges from yellowish brown to gray to almost black. Look for dark brown or black crossbands on their back.
- Heavy-bodied with characteristic rattle on the tail.
The Timber Rattlesnake, which is also known as the Canebrake Rattlesnake, can be found in a wide variety of habitats in western Illinois. Look for these venomous snakes in lowland thickets, high areas around rivers and flood plains, agricultural areas, deciduous forests, and coniferous forests.
Timber Rattlesnake Range Map
Credit: Virginia Herpetological Society
These venomous snakes are ambush predators, waiting for unsuspecting prey to come within range of their strike. They feed primarily on small mammals but may also consume frogs, birds, and other smaller snakes. Timber Rattlesnakes strike their prey and release them, waiting until the venom has taken effect before eating them.
These venomous snakes are potentially the most dangerous species found in Illinois due to their large size, long fangs, and high yield of venom. Luckily, Timber Rattlenskaes have a mild disposition and don’t often bite. They typically give plenty of warning by rattling and posturing.
The Timber Rattlesnake has played an interesting role in U.S. history. As it can be found in the area of the original 13 Colonies, it was used as a symbol during the American Revolution. In 1775 it was featured at the center of the “Gadsden Flag.” This yellow flag depicts a coiled and ready-to-strike Timber Rattlesnake and the words “Don’t Tread on Me.”
#4. Eastern Massasauga
- Sistrurus catenatus
- Adults are typically around 2 feet in length.
- Coloration is gray or light brown with darker chocolate-brown blotches on the back and smaller ones on the sides, which feature light edges.
- Thick body, vertical pupils, heat-sensing pits between the eyes and nostrils, and heart-shaped head.
These small venomous snakes live primarily in wet habitats in Illinois.
The name “Massasauga” actually comes from the Chippewa language and means “great river mouth” and describes their habitat. Look for them in floodplain forests, shrub swamps, low areas along rivers and lakes, wet prairies, moist grasslands, bogs, and marshes. During the summer, they often migrate to drier regions adjacent to these habitats.
Eastern Massasauga Range Map
Unlike other rattlesnakes, the Eastern Massasauga hibernates alone. They frequently hibernate in crayfish burrows but may also use small mammal burrows or spaces under rotting logs or tree roots. Dens must be below the frost line, or they risk freezing to death!
These snakes have cytotoxic venom (poisonous to cells) that destroys tissue, which also has the dangerous quality of disrupting blood flow and preventing clotting. But these snakes are secretive, shy, and avoids humans when possible. The only times they bite seem to be when handled or accidentally stepped on!
This venomous snake is listed as threatened, endangered, or a species of concern in all parts of its range. Historically, these snakes have faced pressure from hunting, and many states had bounties and roundups for them. Today they are still often killed out of fear AND face diminishing wetland habitat.
Do you need additional help identifying a venomous snake?
I recommend purchasing a Peterson Field Guide to the Reptiles and Amphibians of North America. These books have lots of helpful information, including pictures and range maps. View Cost - Amazon
Which of these venomous snakes have YOU seen in Illinois?
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