Illinois is home to a few species of venomous snakes. Encounters are uncommon, as these snakes are generally reclusive. Understanding their characteristics and behavior promotes safety and appreciation.
Identifying Illinois’ Venomous Snakes
Illinois has four native venomous snake species: the Eastern Copperhead, the Timber Rattlesnake, the Eastern Massasauga, and the Northern Cottonmouth. All four are pit vipers, meaning they possess a heat-sensing pit between their eye and nostril, which aids in detecting warm-blooded prey. These pit vipers also typically have a triangular-shaped head and elliptical pupils.
The Eastern Copperhead (Agkistrodon contortrix) averages 24 to 36 inches in length and is recognized by its copper-red head and a body coloration of red-brown or yellow-brown. It features distinctive hourglass-shaped markings across its back that are narrow at the spine and wider on the sides. Copperheads are found in the southern third of Illinois and the lower Illinois River valley, preferring rocky, wooded hillsides and swamps. They are often mistaken for non-venomous northern water snakes due to similar banding.
The Timber Rattlesnake (Crotalus horridus) is a large, stout-bodied snake, typically ranging from 36 to 60 inches long, with some reaching up to 75 inches. Their body can be gray, yellow, or greenish-white with dark, jagged crossbands along the back. A uniform black tail tip is characteristic of adult timber rattlesnakes, and they possess a prominent rattle. These snakes are found in the southern quarter of the state and along the Illinois and Mississippi River valleys, favoring heavy timber with rock outcrops and bluffs. The timber rattlesnake is listed as a threatened species in Illinois.
The Eastern Massasauga (Sistrurus catenatus) is a smaller rattlesnake, usually 18 to 30 inches long. It has a gray or light brown body with large, light-edged, chocolate-brown to black blotches on its back, often described as “bow-tie” shaped. Unlike the timber rattlesnake, the massasauga has four to seven black rings on its tail. This species has nine enlarged, symmetrical plates on top of its head. Eastern massasaugas are found in prairie wetlands and river floodplains, and are listed as endangered in Illinois.
The Northern Cottonmouth (Agkistrodon piscivorus), also known as water moccasin, is primarily found in the very southern tip of Illinois, south of Route 13. It is typically black or dark brown with ragged dark crossbands and has nine large, symmetrical plates on its head. Cottonmouths are semiaquatic and prefer swamps and wet bottomlands. While many non-venomous water snakes are commonly misidentified as cottonmouths, only this one species is venomous.
Encountering and Coexisting Safely
Encountering a snake requires a calm, cautious approach. Snakes generally avoid human interaction and will try to escape. If you see a snake, give it ample space and move away slowly. Never attempt to handle, provoke, or capture any snake, as most bites occur when they feel threatened or are intentionally engaged.
To minimize snake encounters, simple precautions are beneficial. Wear sturdy, closed-toe footwear when walking in wooded, grassy, or wet areas. Watch where you step and place your hands, avoiding unseen crevices or under rocks and logs.
In the rare event of a snake bite, prompt medical attention is necessary. Stay calm and immediately call 911 or local emergency services. While waiting, move away from the snake and keep the bitten area still, ideally below heart level. Remove any jewelry or restrictive clothing from the limb before swelling. Gently wash the wound with soap and water, then cover it loosely with a clean, dry dressing.
Avoid several actions after a snake bite. Do not apply a tourniquet, cut the wound, attempt to suck out venom, or apply ice, as these can cause further harm. Also, avoid alcohol, caffeine, and pain relievers like aspirin or ibuprofen, which can increase bleeding risk.
Understanding Venomous Snake Behavior and Myths
Venomous snakes are often misunderstood. They are generally shy and reclusive, preferring to avoid human contact. They do not “hunt” humans; most bites occur when a snake feels threatened, is accidentally stepped on, or is provoked. Their primary defense is to flee or remain motionless, relying on camouflage.
Most venomous snake bites are not deadly, especially with prompt medical care; for instance, 99.9% of copperhead bite victims survive. While some non-venomous snakes vibrate their tails when threatened, this does not confirm venom. Snakes are not aggressive and will not chase people; they are more likely to escape when confronted.
Snakes play an important role in their ecosystems. They are predators that help regulate populations of rodents and insects. By controlling rodent populations, snakes also limit the spread of diseases. Recognizing their place fosters respect. While caution is prudent, the risk of a venomous snake bite in Illinois remains very low.