Thamnophis

Thamnophis is a genus of snakes, family Colubridae, commonly known as garter snakes, comprising approximately 37 recognized species and 52 subspecies. The genus ranges across North and Central America, from central Canada to Costa Rica, including all lower 48 United States and every Canadian province. Garter snakes are slender bodied with large round eyes and rounded pupils, keeled scales that give a raised texture, and a pattern of longitudinal stripes that in some subspecies appear in blue, yellow or red mixed with black and beige-tan markings; adult length ranges from about 18 to 51 inches. The eastern garter snake subspecies, Thamnophis sirtalis sirtalis, was the first species in the genus scientifically described, by Carl Linnaeus in 1758; other notable members include the widely distributed common garter snake, Thamnophis sirtalis, the giant garter snake of central California, and the endangered San Francisco garter snake subspecies. Garter snakes are among the few snakes considered both mildly venomous, through toxins in their saliva, and poisonous, through toxins sequestered from their prey.