The garter snakes (genusThamnophis) are perhaps the best-known snakes in the USA and Canada. Most are identified by the presence of stripes running the length of their bodies on a dark background. These stripes could be very pronounced and bright, somewhat obscure, or entirely absent, dependent on the species, subspecies, or mutation. A single group of the eastern garter snake,Thamnophis sirtalis sirtalis, could have striped individuals, others in which the stripes are obscure or replaced by a checkerboard pattern, and others which are coal-black and lack all trace of any pattern. Some of the western species, like the checkered garter snake,Thamnophis marcianus, and some western types ofThamnophis sirtalis, are awfully attractive snakes to take a look at.
Most garter snakes show their close relationship to the water snakes in frequenting areas that are outfitted with permanent bodies of water such as lakes, brooks and rivers. Even the sorts of garter snakes found in desert areas follow the courses of streams and brooks. There are some types that are really nautical, taking to the water when alarmed and swimming with the ease of the true water snakes. They depend on flight to escape enemies but when caught will put up a good show of defense, biting energetically and often smearing their captor with a discharge from the anal glands. Captive garter snakes tame swiftly and permit themselves to be handled without any aggressive behaviour whatsoever.
Garter snakes average 2 to 3 feet in length. Some like Butler’s garter snake,Thamnophis butleri, might be fully grown when 18 inches long; the giant garter snake, Thamnophis couchi gigas, on the other hand, grows to over four feet! Garter snakes breed in the spring and the young are born alive in late summer, the broods occasionally numbering one or two dozens. Baby garter snakes can be reared without difficulty even in the most basic types of snake enclosure. The eastern garter snakes feed largely upon earthworms and frogs; the western types have a tendency to favor small fish. Some garter snakes will even take rodents or small birds.
The garter snake is a diurnal snake. In summer, it is most active in the morning and late afternoon; in cooler seasons or climates, it restricts its activity to the warm afternoons. In warmer southern areas, the snake is active year-long; otherwise, it sleeps in common dens, occasionally in great numbers. On warm winter afternoons, some snakes have been noted coming forth from their hibernacula to bask in the sunshine.
While most varieties of garter snake are bounteous, Water contamination, urban enlargement, and home and economic development are all threats to the garter snake. The San Francisco Garter Snake (Thamnophis sirtalis tetrataenia), is now very rare and happens only near pools and reservoirs in San Mateo County, California.
G. Weir is an amateur herpetologist and runs A Pet Snake, an internet site that provides information for folks enthused about snakes and pet snake care.

