IDNR: Thirty-nine species of snakes inhabit Illinois
This page lists 40 snakes: 38 from IDNR's Wild About Illinois Snakes! - Gallery by Family and Species, cross-checked with the INHS "Illinois Species" list and 2 named in other official sources.
4 are venomous by official accounts: Eastern Copperhead, Northern Cottonmouth, Timber Rattlesnake and Eastern Massasauga. IDNR gives a total of 39; the 40 here are the snakes official sources name one by one.
“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.” IDNR
Size
Adults usually about 2 to 3 feet (24-36 in); record about 53 inches.
How to recognize it
Vertical (cat-like) pupils and a heat-sensing pit between eye and nostril
Heavy-bodied; keeled scales
Head shape alone is not a reliable way to identify copperheads
Where in Illinois
Copperheads occur in the southern one-third of Illinois, south of Route 16 and in the lower Illinois River valley … IDNR
JFMAMJJASOND
31 records by month.What the sources say
Venom: “Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.” (IDNR)
Range: 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.
Habitat: Wooded, rocky hillsides and forest edges, sometimes in meadows and fields during summer. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.” (IDNR)
Range: 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.
Habitat: Old fields, floodplain forests, marshlands, and bogs. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
“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.” IDNR
Size
Typically 30 to 48 inches (about 3 to 4 feet); recorded up to 75 inches.
How to recognize it
Heat-sensing pit between nostril and eye; no rattle
Head much wider than the neck, with a dark bar from the eye to the jaw; vertical (cat-eye) pupils
Gapes to show the white lining of its mouth when threatened
Where in Illinois
Cottonmouths live in swamps and wet bottomlands in southern Illinois, south of Route 13. IDNR
JFMAMJJASOND
251 records by month.What the sources say
Venom: “Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.” (IDNR)
Habitat: Cypress-tupelo swamps, sloughs, and oxbow lakes of extreme southern counties. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
“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.” IDNR
Size
Most adults 36 to 60 inches (3 to 5 feet); record 74.5 inches.
How to recognize it
Black tail ending in a rattle
Heat-sensing pit between nostril and eye
Large, thick head distinct from the neck; cat-like vertical pupil
Where in Illinois
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 … IDNR
Venom: “Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.” (IDNR)
Range: 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.
Habitat: Heavy forest along rocky outcrops and bluffs. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Most adults about 42 to 60 inches (3.5 to 5 ft); record 102 inches (8.5 ft). Ranges given by agencies: 41 to 84 in (Louisiana), 36 to 82 in (Oklahoma), adults average 50 to 72 in (Alabama), up to 94 in (NC State Extension), up to 80 in in Colorado and up to 68 in in Arizona.
How to recognize it
Long, slowly tapering tail whose scales look like a braided whip
Very long and slender, with smooth scales
Large eyes with round pupils
What the sources say
Venom: “Of the 40 snakes in Illinois, only four venomous snakes are native to the state:” (Illinois Poison Center)
Habitat: Rocky, open hillsides, glades, and hill prairies. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Forests and edge habitats, commonly near water. Vacant lots in cities. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Photo: U.S. Fish and Wildlife Service - Midwest Region · Public domain · Wikimedia Commons
Adults 22 to 42 inches long, occasionally to 59 inches (Missouri). Pennsylvania gives 24 to over 50 inches; females are usually bigger than males.
How to recognize it
Dark crossbands on the front part of the body break up into rows of blotches from the middle of the body to the tail.
Belly white, yellow or orange, usually with dark half-moon-shaped spots.
Keeled (ridged) scales, so it feels rough; round pupils like other nonvenomous snakes in Missouri.
JFMAMJJASOND
159 records by month.What the sources say
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Streams, lakes, ponds, and ditches. Commonly seen basking on rocks and logs or foraging in the water. Takes shelter under rocks, logs, and other debris along shore. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “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.” (IDNR)
Habitat: Wooded areas, usually those with rocky soils. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Most adults 9 to 13 inches; occasionally up to about 20 inches.
How to recognize it
Dark top of head; a dark spot under each eye and on each side of the neck
Keeled (ridged) scales in 17 rows; round pupil
Tennessee: a small dark downward streak on the side of the head
JFMAMJJASOND
165 records by month.What the sources say
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Variety of forest and prairie habitats, floodplains and uplands, forest edges, even cultivated fields, and especially in vacant lots in cities. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Quiet, permanent backwaters, swamps, sloughs, lakes, and sluggish streams in the southern third of the state, often in very warm water. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Variety of open and former prairie habitats, including intensively cultivated fields and pastures, in the northern half of the state. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “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.” (IDNR)
Habitat: Forest-edge habitats and dry, open woods on clay or sandy loam; sand areas of northern counties. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Lowland forests, in vegetation along banks of sloughs, cypress-tupelo swamps, and other similar bodies of water. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Rocky, wooded limestone hillsides. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Photo: National Park Service from USA · Public domain · Wikimedia Commons
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: The still-water, prairie equivalent of the queen snake, it lives in and along banks of soft-bottomed, heavily vegetated lakes, ponds, sluggish streams, sloughs, and roadside ditches. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Variety of forest, shrub, and edge habitats. Common around farm buildings and abandoned houses. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Rocky, wooded hillsides, hill prairies, bluffs, and adjacent brushy fields. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Prairie wetlands, wet meadows, and grassy edges of creeks, ditches, and ponds, usually in association with crayfish burrows. Has been found in damp habitat remnants in vacant lots of urban settings. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Grasslands and urban lots in former prairie, where it is found under rocks, logs, leaves, boards, and other debris. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Eastern milksnake 24 to 52 inches (Alabama); TN gives 24 to 36 inches for eastern and 21 to 28 for red milksnake.
How to recognize it
Eastern milksnake: black-and-white checkerboard belly (Ohio). Western milksnake in Louisiana: underside dull white with scattered black marks.
Eastern milksnake: a light Y- or V-shaped mark is usually present on the nape
Smooth, shiny scales and round pupils
JFMAMJJASOND
32 records by month.What the sources say
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: A variety of habitats from rocky, wooded hillsides and glades to old fields and wetlands. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Illinois threatened (Illinois E&T checklist, effective Oct 31, 2025: "Mississippi Green Watersnake Nerodia cyclopion")
What the sources say
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Quiet backwater sloughs and cypress-tupelo swamps of extreme southwestern counties. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Photo: Everglades NPS from Homestead, Florida, United States · Public domain · Wikimedia Commons
Most adults about 3 to 5 ft. Sources range from 20 to 56 inches (Florida Museum) to 34 to 77 inches (New Jersey); Alabama says some exceed 6 ft.
How to recognize it
Smooth scales
Long and slender with large eyes
White chin
JFMAMJJASOND
55 records by month.What the sources say
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: A variety of habitats including forests, open areas, and edges of forests near open fields. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Backwater sloughs, cypress-tupelo swamps, and lowland lakes and ponds with abundant vegetation and muddy bottoms. Often seen in nearby forest. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Photo: Photo Credit: Krista Lundgren/USFWS USFWS Mountain-Prairie · Public domain · Wikimedia Commons
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Former black-soil prairies, cultivated fields, pastures, wet meadows and marshes, and vacant lots. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Grasslands from high-quality remnant prairie to degraded brushy fields. Less common in heavily farmed black-soil prairie. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: In and along banks of relatively unpolluted, rocky woodland streams where crayfish are abundant. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “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.” (IDNR)
Habitat: Shallow ponds, sloughs, and swamps containing rotting logs in the Coastal Plain of extreme southern counties. Often crosses roads on rainy nights. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Usually 8 to 10 inches; state figures run from about 4 to 16 inches, with a Florida record of 16.6 inches.
How to recognize it
Plain, unmarked red or orange belly.
Three light spots just behind the head, which may fuse into a collar.
Keeled (ridged) scales in 15 rows at midbody and round pupils.
What the sources say
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Forests and moist woods, occasionally in pastures, bogs, and wet meadows, even in predominantly prairie counties. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Usually 8 to 15 inches long; Alabama reports up to about 18 inches, rarely 24. AZGFD gives a maximum of 34 inches for Arizona animals.
How to recognize it
A yellow, cream or orange ring around the neck; it may be incomplete, and some Lower Florida Keys and western Arizona snakes lack it.
Bright yellow to orange or red belly, often with a row of black half-moon spots; the underside of the tail is often red.
Smooth, shiny scales and a small head only slightly wider than the neck.
JFMAMJJASOND
33 records by month.What the sources say
Venom: “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.” (IDNR)
Habitat: Hill prairies, bluffs, and open forests. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Most adults are 14 to 33 inches long (Florida Museum), with a record of 46 inches. Maryland, Missouri, Tennessee and Arkansas give 22 to 32 inches. The tail is long and thin, about a third or more of the total length.
How to recognize it
Keeled (ridged) scales in 17 rows, which feel rough; the smooth green snake has smooth scales.
Extremely long, thin tail and round pupils.
Large eyes.
JFMAMJJASOND
38 records by month.What the sources say
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Inhabitants of small trees, bushes, and vines, especially near lakes and streams along forest edges. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Mixed woodlands on rocky, sandy soils. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.” (IDNR)
Habitat: Moist prairie remnants, savannas, bogs, marshes, wet meadows, old fields, and vacant lots. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Of the 40 snakes in Illinois, only four venomous snakes are native to the state:” (Illinois Poison Center)
Habitat: Quiet backwaters and cypress swamps in extreme southwestern Illinois. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “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.” (IDNR)
Habitat: Sand prairies, savannas, and adjacent woodlots in well-drained soil. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “Family: Natricidae - … They are harmless to humans.” (IDNR)
Habitat: Border vegetation around permanent bodies of water (swamps, marshes, ponds, rivers, ditches) and along bases of nearby rock outcrops where some individuals hibernate. Climbs onto piles of plants and low bushes. (Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois Urbana-Champaign)
Venom: “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.” (IDNR)
Snakes people confuse
Black Racer or Cottonmouth?
Photo: Everglades NPS from Homestead, Florida, United States · Public domain · Wikimedia Commons
NPS says black racers can resemble the venomous water moccasin and advises leaving alone any snake you cannot identify. It gives no safe field mark, and none is offered here.
Black Racer or Timber rattlesnake?
Photo: Everglades NPS from Homestead, Florida, United States · Public domain · Wikimedia Commons
Report mountain lion, black bear, gray wolf, feral swine, armadillo (north-central/northern counties) and nutria sightings to IDNR through Wildlife Illinois (wildlifeillinois.org/report-sightings/). Report spotted lanternfly with photos to [email protected]. Wildlife Illinois, website authorized by IDNR
Yes. IDNR lists the timber rattlesnake (state threatened) and eastern massasauga (state endangered, federally threatened) among the four venomous snakes. IDNR
“Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.”
“Family: Colubridae - … All of the colubrid snakes in Illinois lay eggs and are harmless to humans.”
“Four species of Ililnois snakes, the eastern copperhead (Agkistrodon contortrix), the northern cottonmouth (Agkistrodon piscivorus), the timber rattlesnake (Crotalus horridus) and the eastern massasauga (Sistrurus catenatus) are venomous.”
“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.”
“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.”
“Family: Natricidae - … They are harmless to humans.”
“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.”
“Illinois snake species hibernate during the cold winter months, becoming active in spring as temperatures and day length increase. … They are generally active during the day, but they can become nocturnal when summer temperatures rise.”
“The timber rattlesnake, Crotalus horridus, has dorsal blotches that are usually uniform in width across the back (not wider at the edges, or ‘bow tie’ shaped as in the Eastern Massasauga) and very narrow, sometimes approaching a chevron.”
“The fox snake, Pantherophis vulpinus, has rounder dorsal blotches (again, not ‘bow tie’ shaped) and only one row of smaller blotches on each side.”
“Of the 40 snakes in Illinois, only four venomous snakes are native to the state:”
“IPC is here to help. Calls to our helpline, 1-800-222-1222, are free and confidential. … Call 911 if someone is unconscious or is having difficulty breathing.”
“Do not attempt to move a snake, even if you think it’s dead.”
“Key Characters: Tail scales patterned like a braided whip; back scales smooth; anal plate divided. Similar Species: North American Racer, Gray Ratsnake.”
“If you have recently seen a mountain lion, black bear, or gray wolf in Illinois, please report the sighting below to the Illinois Department of Natural Resources.”
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