Sistrurus tergeminus
Sistrurus tergeminus, also known as the western massasauga, is a rattlesnake found in the southwestern plains of the United States and northern Mexico. Like all rattlesnakes, it is a pit viper and is venomous. Taxonomy It was once considered a subspecies of the eastern massasauga (Sistrurus catenatus). It contains two subspecies: the nominate S. t. tergeminus, or plains massasauga, found in the Great Plains, and S. t. edwardsii, or desert massasauga, found in the deserts of the Southwestern United States and northern Mexico. The latter is considered "Vulnerable" by NatureServe. According to Campbell and Lamar (2004), a population also exists in southeastern Colorado that is morphologically somewhat intermediate between S. t. tergeminus and S. t. edwardsii. Description Adults range in size from . The standard length for 43 male and 63 female adult specimens was . Conant (1975) mentions an average length of , with a maximum of . The color pattern is similar to that of S. catenatus, but paler: the dark brown blotches contrast strongly with the tan-gray or light gray ground color. The venter (belly) is light with a few dark markings. Common names Western massasauga, ground rattlesnake, Gulf Coast massasauga, víbora de cascabel (Mexico), Edward's massasauga,