Illinois Natural History Survey - University of Illinois

Squamata     suborder Serpentes
Thamnophis proximus -- Western Ribbonsnake

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Alexander 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 Characteristics: Side stripe on scale rows 3-4; orange midback stripe; pair of light spots on top of the head; back scales keeled; anal plate not divided.

Similar Species: Eastern ribbonsnake, common gartersnake, plains gartersnake.

Subspecies: Western ribbonsnake, T. p. proximus.

Description: Medium-sized (up to 90 cm TL), slender black snake with an orange midback stripe and yellow or greenish stripes on each side. Belly greenish white. Tail about one-third of body length. Paired spots on top of head relatively large and partially fused. Usually 8 supralabial scales.

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.

Natural History: A quick, wary snake that climbs and swims readily. Bites when handled. Mates in April or May and gives birth to 10-15 young from July into October that are 15-20 cm TL. Diet mainly of fish and amphibians, especially frogs, and occasionally includes small reptiles. Among its predators are large shore birds, medium-sized mammals, and other snakes. Hibernates in rock crevices and burrows.

Status: Locally common along the Mississippi River valley and in southwestern counties, where cultivation and drainage of wetlands are major threats.


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