"Common Garter Snake"

Color Photograph: Ohio Department of Natural Resources

"Common Garter Snake"

Color Photograph: © Corel Corp.

"San Francisco Garter Snake"

Color Photograph: © Corel Corp.

"Valley Garter Snake"

Color Photograph: Washington Department of Fish and Wildlife

"Red-sided Garter Snake"

Color Photograph: U.S. National Parks Service

"Texas Garter Snake"

Color Photograph: L.A. Dawson. This image is licensed under the Creative Commons
Attribution ShareAlike License v. 2.5:

"Red-spotted Garter Snake"

Color Photograph: © by an courtesy of Ben Amstutz

Common Garter Snake (Thamnophis sirtalis)

Identification:  Snake 18 to 50 inches in length. This widespread snake is extremely variable, both geographically and individually. Short descriptions are given under the Geographical Variation. Characters in common include usually the presence of a dorsal and lateral stripes. Lateral stripes are located on the 2nd and 3rd scale rows. Head usually with 7 labial scales. Dorsal scales keeled and anal plate single.

Geographical Variation:

Eastern Garter Snake (T. s. sirtalis): Midline and lateral lines usually yellow; lateral area between midline and lateral line usually gray-brown with a double row of alternating; coloration, however, individually variable; lateral stripes blue in some Florida populations. Range: Most of the eastern United States and southern Canada. It extends westward to extreme eastern Manitoba and southward through Minnesota, eastern Iowa eastern Missouri to extreme eastern Texas.

Maritime Garter Snake (T. s. pallidulus): Almost identical to the Eastern Garter Snake, but body color lighter and lateral spots more distinct. Range: Newfoundland, Quebec, and southward into northern New England.

Texas Garter Snake (T. s. annectens): Midline stripe large, orange; lateral stripe on scale row 3, extending halfway across rows 2 and 4. Range: Southern Oklahoma southward through east-central Texas.

Red-sided Garter Snake (T. s. parietalis): Midline and lateral stripes yellow; area between midline and lateral stripe dark with red to red-orange spots or short bars; head olive-brown. Range: Extends as far north as the extreme southern Northwest Territories southward through the Prairie Provinces of Canada, to the dakotas, western Minnesota and Iowa, and southward through the Great Plains States to east-central Texas.

New Mexico Garter Snake (T. s. dorsalis): Similar to the Red-sided Garter Snake, but red spots reduced to the areas between the scales on the side of the body. Range: Southern Colorado southward through central New Mexico, into western Texas.

Red-spotted Garter Snake (T. s. concinnus): Body coloration ebon black with a row of prominent red spots along each side; black color of sides extending onto the belly; dorsal stripe thin, yellow, located on dorsal scale row half of each adjacent scale row; lateral stripes may be present or completely covered by the black general coloration; top and sides of head usually with some red coloration. Range: Southwestern Washington and northwestern Washington.

Puget Sound Garter Snake (T. s. pickeringii): Similar to the Red-spotted Garter Snake, but dorsal line confined to the dorsal scale row, not extending to the adjacent rows; top of head all dark. Range: Victoria Island and the adjacent areas of British Columbia and Washington around Pudget Sound.

Valley Garter Snake (T. s. fitchi): Background color of body dark gray, black, or dark brown; dorsal stripe yellow, well defined; top of head all dark; dark areas between the dorsal line and the lateral line with a row or red spots; black on belly confined to the tips of the ventral scales. Range: Most of British Columbia and south into Washington except around Pudget Sound. The population occupies most of Idaho and Oregon, with extensions into western Montana, western Wyoming, and northern Utah. The southern parts of its range included north and central California and western Nevada.

California Red-sided Garter Snake (T. s. infernalis): Similar to the Red-spotted Garter Snake, but red spots less distinct, and background color generally darker; lateral stripes narrower and bright green yellow or their lower margins. Range: Found along coastal California from near the Oregon border to the San Diego region.

San Francisco Garter Snake (T. s. tetrataenia): A pretty snake; dorsal stripe green-yellow, bordered below by a broad red stripe mixed with black; distinct lateral stripes absent; belly metallic greenish blue; top of head red. Range: Found only in the San Francisco Bay region.

Range (see map below left): The Common Garter Snake is possibly the most widespread snake species in North America. It occurs throughout North America with the exception of a large area in the southwestern United States.

Habitat: This species occurs in a wide variety of habitats, but most of the preferred areas are wooded or wet in one form another. For example it is commonly found in meadows, marshes, prairie marshes, wet woodlands, near farms, and suburban areas and parks.

Food: Frogs, salamanders, earthworms, but sometimes also small fish and mice.

Behavior: The Common Garter Snake is often the most common snake around, particularly in the east. It is diurnal and it typically found in wet vegetation. It is the most cold resistant snake species, and is the only snake species found northward into the boreal forest regions of Canada. The Common Garter Snake hibernates in large masses of individuals in the northern parts of its range.

Reproduction:  The Common Garter Snake bears its young alive. Adults mate in the spring. Seven to over 80 young are borne during the summer months between June and August.

Common Garter Snake (Thamnophis sirtalis)

Similar Species:

The wide range of this species, combined with its geographical variability, sometimes makes the Common Garter Snake difficult to separate from the other many species in the genus. However in the central and western parts of North America, populations of the Common Garter Snake have red spots or bars in the dark area between the dorsal and lateral stripes. These red markings should separate it from many other species of Thamnophis in this area.

Some eastern species of Thamnophis

Eastern Ribbon Snake (Thamnophis sauritus)

Short-headed Snake (Thamnophis brachystoma)

Butler's Garter Snake (Thamnophis butleri)

Similar Species