Seiben Ranch below the Forest. They would be expected to occur on the HNF at low to mid- 

 elevations; given the poor accuracy of the Davis (1963) map, any sightings should be 

 documented. Of particular interest would be documentation of any denning sites located. 

 Montana Natural Heritage Program Rank: G5 S5. 



Western Terrestrial Garter Snake {Thanmophis elegans) 



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

 than the Common Garter Snake, their length varying from 18-43". Tliree yellow longitudinal 

 stripes are present (one dorsal, two lateral on the 2nd and 3rd scale rows), 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 is a dusky gray, green or brown, compared to the black or occasionally dark green 

 found in the Common Garter Snake. The ventral surface has a series of dark black/bro\\'n 

 blotches which may cover most of the surface. All black, presumably melanistic, individuals 

 are occasionally found near Townsend. The dorsal scales are keeled and there are normally 8 

 upper labial scales. 

 Young: The coloration of young snakes is similar to that of the adults; young are live-bom. 



Similar species: See Common Garter Snake. 



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

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

 around wetlands. In the HNF area the species was found between 3450 ft in the valley 

 bottom and 6200 ft near McDonald Pass, but probably occurs higher. Females give birth to 

 4-19 young during the summer (Stebbins 1985). 



Surveying: Timed sight surveys may be conducted around wetlands and riparian feeding areas or 

 at denning areas where higher concentrations of garter snakes occur; clear mornings are the 

 best survey times. Much distributional information may come from recording incidental 

 sightings. More intensive research may be done using funnel traps in combination with drift 

 fences. More intensive research and survey projects may use mark-recapture or 

 radiotelemetry techniques. 



Status: Western Terrestrial Garter Snakes were found in the main Rocky Mountains and Big Belt 

 Mountains on the HNF; there are also historic locations just off the forest at the base of the 

 Elkhom Mountains. Given the small number of recent records from tliroughout the area, all 

 records should be documented until the distribution is better understood; of particular interest 

 would be documentation of denning sites. Sightings of elegans from the Elkliom Mountains 

 should be documented to confinii their presence in that range. 



Montana Natural Heritage Program Rank: G5 S5. 



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