Plains Garter Snake {Thamnophis radix) 



Description: The Plains Garter Snake ranges from 16-42" in length and has a dorsal background 

 color of olive, brown, or black. Ii has a prominent orange or yellow dorsal stripe and a 

 greenish-yellow stripe on each side located on the 3rd and 4th scale rows above the belly 

 scales. It typically has black vertical bars on the upper lips. 

 Young: Young are live-bom and resemble adults. 



Similar species: The other garter snakes found in Montana have the lateral yellow lines on the 

 2nd and 3rd scale rows above the belly scales. 



Habitat and Habits:: Plains Garter Snakes are found in prairie habitats but are most common 

 around wetland areas, where they feed around permanent and semi-permanent water bodies. 

 Fish, frogs, toads, mice and invertebrates are the most common food items in the diet of the 

 Plains Garter Snake (Hammerson 1982a, Baxter and Stone 1985). Typical of most garter 

 snakes, they emit a noxious secretion when handled and can be aggressive when disturbed. 

 The Plains Garter Snake is a live-bearer, giving birth to 9-21 young during mid- to late- 

 summer in Colorado (Hammerson 1982a). 



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 may be 

 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: Found over much of eastern Montana. Its status is unclear due to confusion in the 



identification of the 3 garter snakes which occur there. The only location of the Plains Garter 

 Snake from on the Sioux-CNF is an historic record form the Long Pines (Appendix 4). We 

 found one just south of the South Cave Hills during our surveys of the Sioux-CNF; it has 

 also been recorded historically from areas near CNF lands in Montana. It should be watched 

 for in the Sioux-CNF and any sightings should be well-documented with a description 

 written at the time of observation including how radix was distinguished from the other 

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



Montana Natural Heritage Program Rank: G5 S4. 



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