The garter
snake (Thamnophis sirtalis) is one of the most common North American snakes, frequently found in northern temperate latitudes. Its scales have yellowish stripes over a checkered
black and tan background (sometimes with dark green or dark red checks rather than black ones).
Adults generally grow to around 75 cm or so but can often be found over 1 m in length. Like most reptiles, they will often bask to keep warm and prefer temperatures around 30 degrees centigrade. They mate in the spring, after hibernation, and females give live birth in the late summer or early fall. Another round of mating may occur in the fall, with the semen stored as needed until the spring. Litters generally number from one dozen to three dozen young.
Predators include birds of prey, larger snakes such as the king snake, domestic cats, and indigenous carnivorous mammals like mink or opossum. Their primary prey consists of worms, leeches, slugs, small fish, and/or small amphibians. Garter snake saliva is slightly toxic and may cause a mild histamine reaction in some people. In general, you don't have to worry about being bit by a garter snake, although if you startle one it may fart, a stinky defensive reaction whose noise serves a purpose somewhat similar to a rattlesnake's rattle. I swear I am not making this up.
Sources:
anapsid.org
umass.edu/nrec/snake_pit
seventh grade science class