Illinois Natural History Survey - University of Illinois

Squamata     suborder Serpentes
Thamnophis radix -- Plains Gartersnake

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Cook County, IL; photo by Mike Redmer distribution map

Purple shade indicates vouchered specimens. Light blue (cyan) shade indicates photographic records. Yellow shade indicates verified sighting. Slanted hatch indicates pre-1980 records only

NOTE: Not all specimens upon which these maps are based have been verified.


Key Characters: Side stripes on scale rows 3-4; orange-yellow midback stripe; black bars on the margins of labial scales; back scales keeled; anal plate not divided.

Similar Species: Eastern ribbonsnake, western ribbonsnake, common gartersnake, lined snake.

Subspecies: Eastern plains gartersnake, T. r. radix.

Description: Medium-sized (up to 100 cm TL) dark brown or black snake with an orange-yellow midback strip and a yellow-gray stripe on each side. Two rows of alternating black spots or blotches on the side. Belly gray-green with dark spots along the edges. Usually a pair of light spots on top of the head.

Habitat: Former black-soil prairies, cultivated fields, pastures, wet meadows and marshes, and vacant lots.

Natural History: One of the most cold-tolerant snakes, often emerging from hibernation to bask on warm, sunny winter days. Mates in April or May and gives birth to 5-30 young from August through early October. Newborn 15-25 cm TL. Does not bite as readily as the common garter snake when handled. Common prey are earthworms, slugs, and small amphibians. Predators include birds of prey, mammals, and other snakes. Large numbers are killed on roads each spring and autumn as they move to and from upland hibernacula.

Status: Common in the northern half of the state.

 

Illinois Natural History Survey

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