Thamnophis butleri was listed as threatened in 1997.
The Wisconsin Department of Natural Resources has proposed that the Butler's garter snake (Thamnophis butleri) be removed from the state's list of endangered and threatened species. The snake was listed as threatened by the department in 1997, due to habitat loss and fragmentation, as well as the threat of hybridization with the Eastern plains garter snake (Thamnophis radix).
The snake's threatened listing has been controversial as its status as a protected species has pitted environmentalists against land developers, often slowing and even halting construction projects in the state. The DNR says the snake's population numbers have stabilized, with data (abundance, range, and hybridization) released by the University of Wisconsin-Stevens Point bolstering that claim.
The Butler's garter snake, one of five species in the state, is the smallest. It grows to about 15 to 20 inches and feeds mostly on earthworms, leeches, and small amphibians. It can be found in the greater Milwaukee area in six counties; Milwaukee, Ozaukee, Washington, Waukesha,
Fond du Lac and Sheboygan Counties. It lives in open upland and wetland habitats.