Garter snake is a common name for 30 species of harmless colubrid snakes of the genus Thamnophis.
Diets vary among species but include slugs, earthworms, fish and amphibians. Mammals are eaten occasionally, especially by the western garter snake (T. elegans), which restrains such prey by a primitive coiling behaviour. All are live-bearing and normally produce 5-25 young by mid- to late summer but much larger litters are reported occasionally.
Carl H. Ernst and Evelyn E. Ernst, Snakes of the United States and Canada (2003); Douglas A. Rossman, Neil B. Ford and Richard A. Seigel, The Garter Snakes: Evolution and Ecology (1996).