Illinois Natural History Survey - University of Illinois

Crotalus horridus Linnaeus, 1758 -- Timber Rattlesnake

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Key Characters: Small asymmetrical head scales; elliptical pupil; pit between eye and nostril; back with jagged dark bands; rattle or button on tail tip; back scales strongly keeled; anal scale not divided.

Similar Species: Massasauga.

Description: Large (up to 180 cm TL), stout-bodied venomous snake. Back gray, light yellow, or greenish white with 20-25 black, jagged crossbars or blotches. Sometimes an orange or rust stripe down midback. Head clearly larger than slender neck. Dark stripe behind each eye. Tail tip uniformly black in adults. Belly pink, white, cream, or gray, with dark stippling toward sides.

Habitat: Heavy forest along rocky outcrops and bluffs.

Natural History: Active April through October, often seen sunning on rock ledges near winter dens. Forages during summer in upland forests and some border and disturbed habitats where rodents are abundant. Diet mainly small mammals, such as mice, squirrels, and chipmunks. Usually mates July and August with 6-10 young born late summer or early autumn of following year. Newborn 25-35 cm TL. Predators of young include hawks, coyotes, skunks, foxes, and common kingsnakes. Most adult mortality caused by vehicles and wanton killing by humans.

Status: Threatened in Illinois. Relict elsewhere. Threats, besides indiscriminate killing by people, include vehicles and clearing of forest. Previously more widespread, now probably occurs in moderate numbers only in the Shawnee Hills.

Illinois Natural History Survey

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