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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Illinois is home to 40 snake entries on the current Illinois Natural History Survey (INHS) online checklist. Only four are venomous: the eastern copperhead, northern cottonmouth, timber rattlesnake and eastern massasauga. A state Department of Natural Resources (DNR) education page still says 39 species, while its October 2017 brochure says 40; this guide uses the current INHS count and identifies that discrepancy so you know why numbers differ.
Snakes occupy forests, prairies, wetlands, farms, rivers and backyards. Most avoid people. Learning which species occur in the state, where the four pit vipers are generally found and what to do after a bite is more useful than trying to handle a snake for a close look.
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Illinois snake numbers at a glance
| Question | Answer | Qualification |
|---|---|---|
| How many snake entries does Illinois have? | 40 | Current online INHS checklist |
| How many are venomous? | 4 | Confirmed by INHS, DNR and university safety sources |
| How many were listed as threatened or endangered? | 11 | DNR figure stated for 2020 and in an October 2017 brochure; check the current state list before relying on it |
| When are snakes active? | Spring, summer and fall | They hibernate during winter; hot summer weather can shift activity toward nighttime |
Natural Heritage Biologist and herpetologist Scott R. Ballard summarized the older DNR count this way: “Illinois is home to 40 species of snakes. Only 4 of the 40 species are venomous. 11 of the 40 species are listed as endangered or threatened.” That quotation comes from the October 2017 Snakes of Illinois brochure, so the conservation number should be treated as date-specific.
The Illinois snake checklist
The following 38 names and scientific names are the entries reproduced in the verified checklist transcription used for this article. INHS currently enumerates 40 entries online, but two additional rows were not present in the transcription available here. They are deliberately not guessed. If you need a complete field inventory, compare this table with the live INHS checklist and confirm all 40 rows before printing or surveying.
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| # | Common name (INHS spelling) | Scientific name | Venomous? |
|---|---|---|---|
| 1 | Common Wormsnake | Carphophis amoenus | No |
| 2 | Scarletsnake | Cemophora coccinea | No |
| 3 | Kirtland’s Snake | Clonophis kirtlandii | No |
| 4 | North American Racer | Coluber constrictor | No |
| 5 | Coachwhip | Coluber flagellum | No |
| 6 | Ring-necked Snake | Diadophis punctatus | No |
| 7 | Red-bellied Mudsnake | Farancia abacura | No |
| 8 | Plains Hog-nosed Snake | Heterodon nasicus | No |
| 9 | Eastern Hog-nosed Snake | Heterodon platirhinos | No |
| 10 | Prairie Kingsnake | Lampropeltis calligaster | No |
| 11 | Eastern Kingsnake | Lampropeltis getula | No |
| 12 | Eastern Milksnake | Lampropeltis triangulum | No |
| 13 | Mississippi Green Watersnake | Nerodia cyclopion | No |
| 14 | Plain-bellied Watersnake | Nerodia erythrogaster | No |
| 15 | Southern Watersnake | Nerodia fasciata | No |
| 16 | Diamond-backed Watersnake | Nerodia rhombifer | No |
| 17 | Common Watersnake | Nerodia sipedon | No |
| 18 | Rough Greensnake | Opheodrys aestivus | No |
| 19 | Smooth Greensnake | Opheodrys vernalis | No |
| 20 | Great Plains Ratsnake | Pantherophis emoryi | No |
| 21 | Gray Ratsnake | Pantherophis spiloides | No |
| 22 | Eastern Foxsnake | Pantherophis vulpinus | No |
| 23 | Gophersnake | Pituophis catenifer | No |
| 24 | Graham’s Crayfish Snake | Regina grahamii | No |
| 25 | Queensnake | Regina septemvittata | No |
| 26 | Dekay’s Brownsnake | Storeria dekayi | No |
| 27 | Red-bellied Snake | Storeria occipitomaculata | No |
| 28 | Flat-headed Snake | Tantilla gracilis | No |
| 29 | Western Ribbonsnake | Thamnophis proximus | No |
| 30 | Plains Gartersnake | Thamnophis radix | No |
| 31 | Eastern Ribbonsnake | Thamnophis saurita | No |
| 32 | Common Gartersnake | Thamnophis sirtalis | No |
| 33 | Lined Snake | Tropidoclonion lineatum | No |
| 34 | Smooth Earthsnake | Virginia valeriae | No |
| 35 | Eastern Copperhead | Agkistrodon contortrix | Yes |
| 36 | Northern Cottonmouth | Agkistrodon piscivorus | Yes |
| 37 | Timber Rattlesnake | Crotalus horridus | Yes |
| 38 | Eastern Massasauga | Sistrurus catenatus | Yes |
Common names can vary by agency or taxonomic treatment. For example, older DNR material uses “common kingsnake” for Lampropeltis getula, while the INHS checklist uses “eastern kingsnake.” Scientific names provide the most consistent way to compare records.
Which Illinois snakes are venomous?
All four venomous Illinois species are pit vipers. The University of Illinois Division of Research Safety describes the group by a combination of elliptical pupils, a broad triangular head, hinged fangs and a heat-sensing pit between each eye and nostril. Those traits are educational descriptions, not an invitation to approach a snake. Color and head shape can be distorted by distance, lighting, defensive posture and individual variation.
Eastern copperhead (Agkistrodon contortrix)
Copperheads are generally associated with forests and river bluffs. That habitat description is broad: a snake’s location alone cannot confirm its identity. If one is seen, give it room and let it move away rather than trying to photograph facial details or force it into the open.
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Northern cottonmouth (Agkistrodon piscivorus)
Cottonmouths are linked with swamps and other wetlands. Wetland habitat also supports harmless watersnakes, so “near water” is not a reliable identification test. Observe from a safe distance and never pick up a snake to check its mouth.
Timber rattlesnake (Crotalus horridus)
Timber rattlesnakes are usually found in the southern tip of Illinois. The regional clue can help you assess why a sighting is plausible, but it cannot identify an individual animal. A rattle is not required for a snake to be dangerous, and a quiet snake still must not be approached.
Eastern massasauga (Sistrurus catenatus)
Massasaugas occur in prairie wetlands and river flood plains. The species is identified by DNR as state and federally endangered in its species gallery, so disturbing, collecting or killing one creates both safety and conservation problems.
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Juvenile warning
University safety material notes that juvenile Illinois venomous snakes, except timber rattlesnakes, have a bright yellow tail tip. This is another observation to make only from a distance; it is not a reason to handle a young snake.
How to respond when you see a snake
- Stop and create distance. Keep children and pets back, avoid blocking the snake’s route and do not corner it.
- Do not handle it. The Illinois Poison Center says not to intentionally handle, trap, feed or move a snake, including one that appears dead. A dead-looking snake can still injure someone through a reflex bite.
- Do not rely on one visual trait. Head shape, pupils, tail markings and habitat can orient an experienced observer, but none is a safe field test by itself.
- Leave relocation to trained personnel. If a snake is inside a building or presents an immediate hazard, keep people away and contact an appropriate local wildlife or animal-control service rather than attempting capture.
What to do after a snakebite
Treat any suspected venomous bite as an emergency. The Illinois Poison Center’s instructions are to go to the nearest emergency department immediately. Do not wait for swelling, pain or other symptoms to develop.
- Move away from the snake without trying to catch it. A photograph taken from a safe distance can help clinicians, but identification is never worth another bite.
- Keep the bitten limb still and immobilized. Limit movement while arranging emergency transport.
- Remove rings, watches and other jewelry. Swelling can make these items constrict the limb.
- Do not use harmful home treatments. The poison center specifically warns against ice or heat, a tight tourniquet, electric shocks, suction and cutting the wound.
- Call for expert guidance if needed. The Illinois Poison Center helpline, 1-800-222-1222, is staffed by toxicology experts 24 hours a day, seven days a week; it does not replace immediate emergency evaluation.
University of Illinois Extension also advises immediate emergency attention and warns that trying to kill or collect a snake can cause another strike.
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Where Illinois snakes live and when they are active
DNR describes Illinois snake habitat at the broad landscape level: forests, grasslands, marshes, swamps, ponds, lakes, streams, rivers and sloughs. The 40 checklist entries therefore represent very different ecological niches. Watersnakes and crayfish snakes are associated with aquatic settings, while racers, ratsnakes, kingsnakes and many gartersnakes use terrestrial habitats; the checklist alone does not provide a uniform habitat profile for every taxon.
Snakes are generally active in spring, summer and fall and hibernate during winter. During very warm summer conditions, activity may shift toward nighttime. Snakes are solitary predators, and DNR lists prey that includes invertebrates, fish, lizards, birds, rodents and other small mammals. Their presence can help regulate prey populations, even when people would rather not encounter one.
Conservation and legal considerations
DNR identifies habitat alteration and loss, illegal reptile trade and fear-driven killing as major conservation concerns. Its education page reported 11 Illinois species as state endangered or threatened as of 2020, and the 2017 brochure gives the same number. Because legal designations can change, consult the current Illinois list before describing any species as protected today.
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The October 2017 DNR brochure states that permits were required for work with or collection of snakes on public lands, that personal possession limits applied to native species and that buying, selling, trading, bartering or breeding wild-caught Illinois snakes and their offspring or Illinois-origin lineages was illegal. Those are historical brochure statements, not a complete current legal code. Check current Illinois statutes, administrative rules and agency guidance before collecting, transporting, possessing or trading a snake.
For ordinary residents, the safest conservation action is simple: do not kill, collect or relocate snakes yourself. Preserve native habitat, keep domestic animals away from wild snakes and allow an animal to leave on its own.
Using the checklist responsibly
A species list is a starting point, not a field-identification license. Record the date, county or broad locality, habitat and behavior from a safe distance. Avoid handling and avoid publishing an exact location for a rare or protected snake. If a definitive identification matters for a scientific survey, contact a qualified herpetologist or agency biologist.
For a complete visual guide, use the INHS species pages and current DNR species material alongside this checklist. Those sources can supply photographs and species-specific descriptions, while the safety guidance here explains why no photograph or single trait should prompt close contact.
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