Western Terrestrial Garter Snake {Thamnophis elegans). 



Description: Adult Western Terrestrial (or Wandering) Garter Snakes are smaller in body size 

 than the Common Garter Snake, their snout-vent length varying from 40-70 cm. Three 

 yellow longitudinal stripes are present (one dorsal, two lateral), but the dorsal stripe is much 

 narrower than that of the Common Garter Snake. A distinctive feature of the Western 

 Terrestrial Garter Snake is a series of alternating black spots which run the length of the body 

 between, and somewhat on, the yellow stripes. The background color between the stripes 

 tends to be more gray compared to the dark brown found in the Common Garter Snake. The 

 ventral surface has a series of dark black/brown blotches which may cover most of the 

 surface. The dorsal scales are keeled and there are normally 8 upper labial scales. Females 

 give birth to 4-19 young during the summer (Stebbins 1985). The coloration of young snakes 

 is similar to that of the adults. 



Habitat and Habits: The habitat and habits of the Western Terrestrial Garter Snake are similar to 

 the Common Garter Snake, i.e., they are foimd in most habitats but are particularly common 

 around wetlands. Most records from the BNF area are below 5000' elevation. The highest 

 elevation noted during the 1 995 survey was 6400' on the St. Mary Peak road on 1 August, 

 but this species could occur up to treeline in appropriate habitat. Individuals have been 

 encountered between 27 April and 26 October in the BNF area. Young snakes (25-35 cm 

 total length) were seen between 22 May and 31 August in 1995; the larger individuals 

 measured in 1995 were 50-55 cm total length. 



Surveying: Surveys using mark-recapture techniques or sight surveys can be conducted in areas 

 of higher concentrations around marshes and bogs. Roads can be driven slowly while 

 looking for basking snakes or roadkills. 



Status: Western Terrestrial Garter Snakes have been found on all districts of the BNF; during 

 1995 the species was reported from all but the Sula District. This snake species is probably 

 more widespread and abundant than current documentation indicates. Sightings, especially 

 from higher in the movmtains, should be reported. 



Montana Natural Heritage Program Rank: G5 S5. 



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