Thamnophis elegans terrestris - Coast Gartersnake

Nonvenomous

Gartersnakes have toxins in their saliva which can be deadly to their prey and their bite might produce an unpleasant reaction in humans, but they are not considered dangerous to humans.

Size

Thamnophis elegans measures 18 - 43 inches in length (46 - 109 cm).

Appearance

A medium-sized slender snake with a head barely wider than the neck and keeled dorsal scales. Color and pattern is highly variable, but there is usually a yellow dorsal stripe and a yellowish stripe along the bottom of each side. The underside is yellowish to bluish-gray with varying amounts of reddish markings.

One color phase consists of a yellow dorsal stripe and two distinct yellowish or whitish side stripes, with black checkered spots on the sides inbetween the stripes on a reddish ground color, creating a red and black checkerboard appearance. This phase occurs primarily on the San Francisco peninsula and north along the coast into Marin County and possibly farther.

On some snakes in the Santa Cruz Mountains and the Monterey Bay area, the side stripes are reddish, with varying degrees of checkering or barring of the black on a reddish ground color.

Another color phase consists of almost completely solid dark coloring between distinct light side and dorsal stripes, with little or no red. This phase is most common from Santa Cruz County south.

On some snakes the ground color is almost completely solid dark, the dorsal stripe is yellow, but the side stripes are reddish. We include pictures here of this phase from the East Bay hills, the Santa Cruz Mountains, and southeast Marin County near the S.F. bay.

Along the north coast, the dark coloring can become light brown with little red, or with a heavy red wash over the sides. Snakes here can also have three yellowish stripes, a reddish ground color with some black markings, and a dark bar beneath each side of the dorsal stripe.

Behavior

Active in daylight. Chiefly terrestrial - not as dependant on water as other gartersnake species, but more likely to be found near water. When frightened, this species will sometimes seek refuge in vegetation or ground cover, but it will also crawl quickly into water and swim away from trouble. If frightened when picked up, this snake will often strike repeatedly and release cloacal contents and musk.

Diet

This snake eats a wide range of prey (among the widest of any snake species), including amphibians and their larvae, fish, birds, mice, lizards, snakes, worms, leeches, slugs, and snails.

Reproduction

Breeds primarily in spring, with young born live July - Sepember.

Range

This subspecies, Thamnophis elegans terrestris - Coast Gartersnake, occurs along the Pacific coast from southern Oregon to Ventura County.

The species Thamnophis elegans - Western Terrestrial Gartersnake, ranges widely from the California coast north into Canada and east to NewMexico, Colorado, Wyoming, Montana, and South Dakota, with an isolated population in Baja California Norte, Mexico..

Habitat

Inhabits mixed woodland, grassland, coniferous forest, dunes, brushland, generally in the vicinity of ponds or flowing water.

The species Thamnophis elegans - Western Terrestrial Gartersnake, occurs from sea level to 13,100 ft. (3,990 m) in elevation in Colorado. (Stebbins, 2003).

Taxonomic Notes

T. e. vagrans intergrades with T. e. elegans in northeast California in Modoc and eastern Siskiyou counties and in south central Oregon (this snake was formerly classified as the subspecies Thamnophis elegans biscutatus - Klamath Gartersnake. Intergrades with T. e. elegans also occur along the southern and southeastern edge of the Sierras.

Three subspecies of Thamnophis elegans are found in California - T. e. vagrans - Wandering Gartersnake, T. e. e.egans - Mountain Gartersnake, and T. e. terrestris - Coast Gartersnake.

Rossman, Ford, and Seigel (1996) emphasize that a detailed study of geographic variation throughout the range of Thamnophis elegans is badly needed.

Bronikowski and Arnold (2001, Copeia 2001:508-513) found several clades within T. elegans that do not always follow the subspecies boundaries, and concluded that there was no support for the race terrestris. Presumably, the former T. e. terrestris snakes become T. e. elegans.

Hammerson (1999, Amphibians and Reptiles of Colorado. 2nd ed. Univ. of Colorado Press) synonymized T. e. arizonae and T. e. vascotanneri but retained three subspecies, T. e. vagrans, T. e. elegans, and T. e. terrestris. Conservation Issues (Conservation Status) This species is not known to be threatened, but gartersnakes have been negatively impacted by competition with introduced bullfrogs and non-native fish in some areas.