The eastern massasauga rattlesnake (Sistrurus catenatus catenatus) is a candidate for federal listing as a threatened or endangered Distinct Population Segment (DPS) (U.S. FWS 2003). Although the massasauga rattlesnake is thought to be in decline throughout much of its range, only the eastern subspecies (Sistrurus c. catenatus) is currently under consideration for listing. The eastern subspecies has been described as historically ranging from central New York and southern Ontario, southwest to Iowa and Missouri (Johnson 1995; Minton 2001). This eastern subspecies encompasses all S. catenatus residing north and east of the Missouri River.