The common garter snake, or Thamnophis sirtalis, is a species native to North America. These snakes can be found throughout much of the continent, though they are typically not suited to the desert environments of the Southwest. The common garter snake and its many subspecies may have a variety of markings, but all of these snakes are considered nonvenomous. These snakes appear to have adapted well to human encroachment, and are considered to be thriving as a species.
An adaptable species that can flourish in a number of environments, the common garter snake is often equally at home in rural, urban, and suburban areas. These snakes generally prefer a temperate, humid habitat, and can be found in swamps, marshes, forests, and meadows. They often make their homes near lakes, ditches, streams, and ponds. They can also occupy parks, gardens, lawns, vacant lots, and farms.
The markings of these snakes might vary greatly from one individual to the next. Most common garter snakes bear a pattern of three narrow stripes running the length of the body. The color of the stripes can vary from blue to white, green, yellow, or brown. The body itself may be gray, olive green, brown, or black. Rows of spots may appear between the stripes. The common garter snake's head is usually darkly colored, without markings, and wider than the rest of its body.
This type of snake can reach lengths of 14 to 48 inches (46 to 137 cm). These diurnal snakes are usually active during daylight hours, and they can withstand a wider range of temperature changes than some other species of snake. They do, however, need to bask in the sun to maintain an appropriate body temperature, and will often congregate for warmth when resting or hibernating.
These snakes typically feed on small animals, including toads, frogs, and crayfish, as well as insects, earthworms, slugs, and snails. Other snakes, fish, crayfish, and leeches may form part of the common garter snake's standard fare. Breeding generally occurs during the spring season, and the young are normally born alive in late summer or autumn. These snakes may reach maturity at two to three years of age, though they continue to grow throughout their lives. The average lifespan of the common garter snake in the wild is about two years, but they can live as long as ten years when kept in captivity.