Plains Garter Snake {Thamnophis radix) 



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



background color of olive, brown, or black. It 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 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. All the Plains Garter Snakes I have seen or 

 heard about from Montana, have orange dorsal stripes. 



Habitat and Habits: The habitat and habits of the Plains Garter Snake are similar to those of the 

 Common Garter Snake. 



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, but appears to be moderately common 

 in the eastern 1/3 of Montana. In the vicinity of the study area it has been found near 

 Freezeout Lake, the second westernmost record for this species in the U.S. [a sight record 

 along the Cut Bank River in Glacier County is the westernmost]. It should be watched for in 

 prairie or shrub-steppe areas near water at lower elevation of the study area 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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