Butler's Gartersnake Thamnophis butleri - Endangered

Adult from Michigan

Identification

Butler's Gartersnakes are small, striped snakes that are easily confused with their much more common and widespread relative: the Common Gartersnake. Most Butler's Gartersnakes are dark brown in color with white to yellow dorsal and lateral stripes. This diminutive snake rarely exceeds two feet (60 cm) in length and reaches maturity at just over a foot (35 cm) in length. Their head is notably smaller than other Thamnophis and the neck is indistinct.

Eastern Gartersnakes are easily confused with this species and are much more likely to be encountered in Indiana. There is a notable size difference between the two species and any snake over two feet (65 cm) long is almost certainly an Common Gartersnake. Though Common Gartersnake are larger and have a more distinct head and neck, the most reliable way to differentiate the two species is by determining which scale row the lateral stripes overlay. In T. sirtalis, the lateral stripes fall on the second and third row of scales (counting up from the underbelly) whereas the stripes overlap the third and fourth scale rows in T. butleri. Eastern Ribbonsnakes are similar in coloration and pattern, but are a long and slender snake by comparison, with a much longer tail.

Ecology and Conservation

Butler’s Gartersnakes prefer moist, open, grassy habitats such as wet meadows and prairies, the borders of marshes and lakes, pastures, fields in parks, as well as other moist, open areas. They may use heavily disturbed sites such as abandoned lots and railroad right of ways. The diet of the Butler’s Gartersnake is comprised almost exclusively of earthworms. Butler’s Gartersnakes are active from spring through late fall. Exact dates vary geographically and with local conditions, but typically range from late March to early April through October or November. The breeding activities of the Butler’s Gartersnake begin almost immediately after emergence from hibernation. Butler’s Gartersnakes have been observed to hibernate in ant mounds, mammal burrows, and also possibly in crayfish burrows.

The foremost threat facing Butler’s Gartersnakes is habitat loss. Many known Butler’s Gartersnake populations currently reside in urban areas. Natural ecological succession may also threaten existing populations of Butler’s Gartersnakes, particularly those existing in highly fragmented areas. Collection has seriously impacted some populations, particular in urban settings. The Butler’s Gartersnake is listed as state Endangered in Indiana and state Threatened in Wisconsin.

Distribution

Butler's Gartersnakes are apparently rare in Indiana, known from only a few scattered localities in northeastern quadrant of the state. The distribution of the Butler’s Gartersnake is highly fragmented within its range. Its distribution extends from central Ohio, west to central Indiana, north through eastern Michigan and into the adjacent southern portion of Ontario, Canada. Disjunct populations can also be found in southeastern Wisconsin and in the central peninsula of southern Ontario.

Within the Midwestern states the Butler’s Gartersnake is found within the northeast quarter of Indiana, in the eastern and southern Lower Peninsula of Michigan, across the northern two-thirds of Ohio and from southeastern Wisconsin. The species is absent from Illinois, Iowa, Minnesota and Missouri.

Taxonomy

No subspecies of the Butler's Gartersnake are currently recognized.

Literature Cited

Carpenter, Charles Congden. 1951. Comparative ecology of the common garter snake (Thamnophis s. sirtalis), the ribbon snake (Thamnophis s. sauritus), and Butler's garter Snake (Thamnophis butleri) in mixed populations. Ph.D. Dissertation, U. Mich., Ann Arbor, Mich. 195 pp.

Carpenter, Charles C. 1952. Comparative ecology of the common garter snake (Thamnophis s. sirtalis), the ribbon snake (Thamnophis s. sauritus), and Butler's garter snake (Thamnophis butleri) in mixed populations. Ecol. Monogr. 22: 235258.

Carpenter, C.C. 1953. A study of hibernacula and hibernating associations of snakes and amphibians in Michigan. Ecology, 34:74-80

Catling, P.M. and W. Freedman. 1977. Melanistic Butler's garter snakes (Thamnophis butleri) at Amherstburg, Ontario. Canadian Field-Naturalist 91: 397-399.

Catling, P.M. and W. Freedman. 1980a. Variation in distribution and abundance of four sympatric species of snakes at Amherstburg, Ontario. Canadian Field-Naturalist 94(1): 19-27. Catling, P.M. and W. Freedman. 1980b. Food and feeding behavior of sympatric snakes at Amherstburg, Ontario. Canadian Field-Naturalist 94: 28-33.

Conant, R. 1951. The reptiles of Ohio. 2nd Edition. Notre Dame Press, Notre Dame, IN. Ernst, C. H. and R. W. Barbour. 1989. Snakes of Eastern North America. George Mason University Press, USA.

Ford, N.B., and D.W. Killebrew. 1983. Reproductive tactics and female body size in Butler’s Garter Snake, Thamnophis butleri. Journal of Herpetology 17:271275.

Harding, J.H. 1997. Amphibians and reptiles of the Great Lakes Region. The University of Michigan Press, Ann Arbor, MI.

Logier, E.B.S. 1939. Butler's Garter-snake Thamnophis butleri in Ontario. Copeia 1939: 20-23.

Minton, S.A. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science, IN.

Distribution Map
Distribution map of Butler's Gartersnake (Thamnophis butleri)
Photographs