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Canadian Amphibian and Reptile Conservation Network - Réseau Canadien de 
Conservation des Amphibiens et des Reptiles

Thamnophis butleri
Couleuvre à Petite Tête / Butler's Gartersnake

Couleuvre à Petite Tête

The Gartersnakes, and other live-bearing, harmless snakes, which were included within the Family Colubridae, have recently been placed in the Family Natricidae.

The smallest of Ontario's three members of the genus Thamnophis. It grows to only 69 cm in total length, but typically is less than 50 cm. It is a brown snake with two yellow or orange side stripes and a stripe down the center of its back.

Confusing Species
Butler's Gartersnake is very similar to both the Common Gartersnake and the Ribbonsnake. The placement of the side stripes is diagnostic in these closely related species. In Butler's Gartersnake the stripes occupy the 3rd scale row and part of the 2nd and 4th row. The stripe is confined to the 2nd and 3rd scale rows of the Common Gartersnake and the 3rd and 4th rows of the Ribbonsnake.

Butler's Gartersnake is limited to just three small, widely separated areas in southwestern Ontario. These disjunct populations imply that at one time Butler's Gartersnake may have been more widespread in Ontario, during an earlier, warmer climate. Outside of Canada, it also has a limited distribution. Its range is centered on the southern Great Lakes and it is not found south of Ohio.

This Gartersnake tends to be associated with grassy or prairie-like areas. It may make use of vacant lots in urban or suburban areas. Although frequently found under cover such as boards or rocks, this may simply be because they are virtually impossible to locate when hunting in grass.

Mating occurs in the spring and the young are born in the summer -- females do not lay eggs. Up to 16 offspring have been recorded although 8-10 are more common. Newborns are roughly 15 cm in length at birth.

Natural History
Butler's Gartersnake feeds mainly on earthworms. It also eats insects and even small frogs. Butler's Gartersnake can move very quickly in long grass although it is very awkward in unvegetated areas, where it moves with a great deal of "side-winding." It is less active during the day. It is unknown where individuals overwinter in Canada, but in the US, individuals have made use of animal burrows.

Conservation Concerns
The extremely limited distribution of Butler's Gartersnake make it more vulnerable than wide-ranging species. The range has contracted as a result of habitat loss, primarily due to agriculture. The Canadian portion of the range is not just the northern fringe of its distribution, as it comprises a significant percent of the entire range. Given its limited distribution, Butler's Gartersnake is designated Threatened in Canada by COSEWIC.