Eastern Gartersnake

Thamnophis sirtalis sirtalis

eastern_gartersnake_10-28-11.jpg

Eastern gartersnake
Eastern gartersnake
Other Common Name
Eastern Garter Snake
Family

Colubridae (nonvenomous snakes) in the order Squamata

Description

The general color of the eastern gartersnake is variable; it may be blackish, dark brown, greenish, or olive. There are usually three yellowish stripes, one down the back and one along each side. The area between the stripes on each side may have a double row of alternating dark spots. The belly is yellowish green with two rows of faint black spots that are indistinct, somewhat hidden by the overlapping scales. Scales on the back are keeled; the anal plate is single. When cornered, this snake often flattens its head and body and tries to strike. Like many kinds of harmless snakes, gartersnakes will bite to defend themselves.

Another subspecies, the red-sided gartersnake (Thamnophis sirtalis parietalis), is found in the western half of the state. It has some degree of red or orange-red skin that shows along its sides.

Size

Length: to 18–26 inches.

Red-sided Gartersnake

Red-sided Gartersnakein Springfield, MO
Red-sided Gartersnake
Habitat and conservation

Eastern gartersnakes live in a variety of habitats but favor areas near water, such as near ponds, marshes or swamps and in damp woods or forested areas along creeks and rivers. They also live in empty lots and old abandoned farms. They are often found under boards, rocks, or other objects in city lots and near farm buildings. In winter, they take shelter in animal burrows or congregate in deep cracks in south-facing limestone bluffs or rocky hillsides.

Foods

Eastern gartersnakes eat frogs, tadpoles, toads, salamanders and earthworms. Occasionally they eat minnows, small mice, and small snakes of other species.

image of Eastern Gartersnake Eastern Garter Snake Distribution Map
Distribution in Missouri

Occurs in the eastern half of the state; the red-sided gartersnake subspecies (Thamnophis sirtalis parietalis), with red on its sides, is in the western half (the prairie region of western and northern Missouri).

Status

The most common of our gartersnakes.

Life cycle

This species is normally active in March through early November but may be active anytime in a mild winter. Hunting occurs in daytime. Courtship and mating is usually in spring, soon after emergence from the overwintering retreat. A number of males may try to court and mate with a single female, with much writhing as the males try to rub against the female. Females give birth to live young in late summer and early fall; a litter may contain 4–85 young, but usually about 12.

Human connections

Fear and myth still surround snakes, due largely to a lack of knowledge about them. Fortunately, the biology and natural history of Missouri snakes are both interesting and enjoyable to learn. People who understand snakes tolerate and appreciate them as a natural part of outdoor Missouri.

Ecosystem connections

As predators, gartersnakes help keep populations of other animals in check. Although they can defend themselves by trying to bite and by smearing foul-smelling musk on attackers, they and their young provide food for many predators.