Butler's Gartersnake (Thamnophis butleri)

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Status: State Threatened (1997).

Occurrence: Generally found only in the extreme southeastern counties of Wisconsin.

Aid to ID: 15-20 inches (38-51cm). Medium sized snake, with a shorter, narrower head than other Wisconsin gartersnakes. The narrow, small head accompanies a thicker body, resulting in less of a constriction behind the head than is observed in most snakes. Dorsal ground color is brown, black, or olive with or without a double row of black spots between the stripes. The distinct lateral stripes are on scale row three and adjacent rows of two and four anteriorly and most of scale rows two and three posteriorly. Stripes vary from light yellow to a rich orange-yellow color. The ventral surface is green to yellow-green with dark spots on the lateral edges. This snake exhibits a peculiar escape behavior; when excited, it will vigorously wriggle from side to side, making little forward progress.

Habitat: Prefer wet-mesic prairies, marshes, roadside grassy areas, and vacant city lots.

Food Habits: The principal food is earthworms, but leeches, fish, and toads are sometimes consumed as well.

Natural History:

Active: Mid-March through early November.
Hibernation: Is a communal hibernator like other gartersnakes.
Reproduction: Both sexes mature in their second spring. Mating occurs from late March to late April. Ovoviviparous; 4 to17 young born between July and mid-September.

Management Considerations: Many of the populations of this species have been isolated from each other due to wetland loss and habitat fragmentation. This species already has a limited range, so habitat destruction is especially detrimental to them. Another concern is genetic swamping by T. radix; this closely related species moves into the range of T. butleri and breeds with them. There are believed to be only a handful of populations that exhibit only the T. butleri characteristics, most of these occurring within Milwaukee County, the most urbanized county in the state.

This species may be inadvertently sold as the common gartersnake in pet stores due to its gross resemblance to this and other gartersnakes. Conservation wardens and DNR employees involved in DNR permitting processes in southeast Wisconsin should familiarize themselves with the unique characteristics of this species to help minimize future impacts to remaining populations.

See Also:
Living with Snakes

Information compiled from publication ER-091.

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