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Wild About Illinois Snakes! - Family Crotalidae

​Photos © Scott Ballard. No photographs included within this information may be used on the internet, publications or any other form of media without the photographer's express permission. All rights reserved.
 
 
copperhead (Agkistrodon contortrix) Photo © Scott Ballard
The copperhead averages 24 to 36 inches in length. It has a heat-sensitive pit on each side of the head between the eye and the nostril. The head is flattened and much wider than the neck. The pupil of its eye is vertically elliptical. Scales are weakly keeled (ridged). This snake's coloration is as follows: copper-colored head; red-brown or yellow-brown body; hour-glass markings across the back when viewed from above.
 
The copperhead lives in rocky, wooded hillsides, abandoned sawdust piles and swamps. This snake is active during the day in spring and fall, becoming nocturnal in the hottest summer months. When disturbed it will attempt to run away. If trapped, it rapidly vibrates the tip of the tail, making a noise against whatever the tail hits. This species may be found in groups, particularly in fall when moving to hibernating dens. Mating occurs in the spring. The female gives birth to a brood of between one and 14 young in August or September. Each female may produce young only every other year. This snake injects prey with venom then waits for it to succumb before eating it. The copperhead eats mice, small birds, lizards, snakes, amphibians and insects. In Illinois, it lives in the southern one-fourth of the state and in bluffs along the southern section of the Mississippi River.
 
 
cottonmouth (Agkistrodon piscivorus) Photo © Scott Ballard
The cottonmouth averages 30 to 42 inches in length. It has a heat-sensitive pit on each side of the head between the eye and the nostril. The head is flattened and much wider than the neck. The pupil of each eye is vertically elliptical. The scales are weakly keeled (ridged). This snake may be plain black or brown above with little evidence of a pattern. Some individuals have dim crossbands across the back.
 
The cottonmouth lives in sloughs and swamps. This snake is semiaquatic and is mainly active at night. When disturbed, it will either stay where it is and vibrate its tail or slowly crawl away. It may move its head up and back with the mouth open showing the white interior, hence its name of "cottonmouth." This snake hibernates in dens in rock crevices with other species of snakes. Mating occurs mainly in the spring but may occur at any time the snake is active. The female gives birth to a brood of from one to 15 young in August or September. The tip of the young cottonmouth’s tail is yellow. The cottonmouth injects prey with venom then waits for it to succumb before eating it. This snake eats fishes, mice, small birds, lizards, snakes, amphibians and insects. In Illinois, it lives in the southern one-fourth of the state.
 
 
 
timber rattlesnake (Crotalus horridus)* Photo © Scott Ballard
The timber rattlesnake averages 36 to 60 inches in length. It has a heat-sensitive pit on each side of the head between the eye and the nostril. Its head is flattened and much wider than the neck. The pupil of each eye is vertically elliptical. A rattle is present at the tip of the tail. The scales are keeled (ridged). The body is gray, yellow or green-white with a series of dark bands along the back. A rust-colored stripe is present in the middle of the back. A dark bar may be found between the eye and jaw.
 
The timber rattlesnake lives in forested bluffs, abandoned sawdust piles and rock outcrops and may be found in fields in summer. This snake is active during the day until temperatures become too high in summer. It then becomes nocturnal. Much of the time is spent hiding. The rattle is developed as the skin is shed. A button at the tip of the tail is present at birth. Each time the skin is shed a new segment is added to the rattle. The snake may shed its skin from three to five times in a year. Counting segments of the rattle is not a good method of aging a snake as the number of segments added each year varies and segments may be broken or lost. When disturbed, it will try to escape or coil and rattle the tip of the tail producing a buzzing noise. It hibernates in dens in rock crevices with other species of snakes. Females reach maturity at the age of four or five years. Mating may occur in spring or fall. The female gives birth to from five to 17 young in August, September or October of the following year. Mature females reproduce every other year. This snake injects its prey with venom then waits for it to succumb before eating it. The timber rattlesnake eats rodents and birds but will take frogs and lizards. In Illinois, it lives in the southern one-fourth of the state and in bluffs along the Illinois and Mississippi rivers.
 
 
 
massasauga (Sistrurus catenatus)** Photo © Scott Ballard
The massasauga averages 18 to 30 inches in length. It has a heat-sensitive pit on each side of the head between the eye and the nostril. Its head is flattened and much wider than the neck. The pupil of each eye is vertically elliptical. A rattle is present at the tip of the tail. Scales are keeled (ridged). A row of dark blotches is present down the back, and there are three rows of dark spots on the sides. The body is gray.
 
The massasauga lives in wet prairies, peatlands and old fields. This snake is active in the day, except in the hottest summer months when it becomes nocturnal. The massasauga may take shelter in crayfish burrows or other underground cavities. It may be seen basking on grass, near crayfish burrows or in other open locations. If disturbed it may shake its rattle. The rattle is developed as the skin is shed. A button at the tip of the tail is present at birth. Each time the skin is shed a new segment is added to the rattle. The snake may shed its skin from three to five times in a year. Counting segments of the rattle is not a good method of aging a snake as the number of segments added each year varies, and segments may be broken or lost. Mating may occur in spring or fall. Females mature after three to four years and reproduce every other year. The female gives birth to five to 14 young in August or September, the number depending on her size and age. This snake eats mice, small birds, frogs and snakes. It is found in only a few locations in northern Illinois, central Illinois and south-central Illinois.
 
* = threatened in Illinois
** = endangered in Illinois