California Garter Snakes

Thamnophis atratus or the Aquatic Garter Snake is a species of colubrid snake residing exclusively along the coast of Oregon and California. Two subspecies are currently recognized. One variety of the snake has a blue-gray background color with a faint olive colored dorsal stripe and white dots along its sides. Another morph has a yellow dorsal stripe with black spots along its sides. The second variation is the more classic garter snake look however, due to... less ↑

Comments: Habitats of this highly aquatic snake include pools of permanent or seasonal streams (often rocky), meadow ponds, lakes, reservoirs, and associated riparian zones (e.g., cottonwood, willow, sycamore, alder), in areas with oak woodland, grassy valleys, chaparral, montane coniferous forest, or (east of the Sierra crest) pine-juniper-sagebrush (Rossman et al. 1996, Ernst and Ernst 2003, Stebbins 2003). less ↑

Most western terrestrial garter snakes have a yellow, light orange, or white dorsal stripe, accompanied by two stripes of the same color, one on each side. Some varieties have red or black spots between the dorsal stripe and the side stripes. It is an immensely variable species, and even the most experienced herpetologists have trouble when it comes to identification. They are medium-sized snakes, usually 46–104 cm (18–41 in).

Like many species of North American garter snake, the Western terrestrial garter snake possesses a mildly venomous saliva. Specimens collected from Idaho and Washington State produced venom with myonecrotic (destroys muscle tissue) effects when injected into the gastrocnemius muscles of mice. Several cases of mild human envenomation with local edema and other symptoms (but without any systemic symptoms) have occurred from the wandering garter snake subspecies, including in Colorado.

This species is the only garter snake species with a well-documented tendency to constrict prey, although the constriction is inefficient when compared with the constriction of many other snakes (such as the gopher snake), involving disorganized, loose, and sometimes unstable coils and a longer time required to kill prey. Snakes from Colorado populations of terrestrial garter snakes appear to be more efficient at killing their prey by constriction than those from Pacific Coast populations.

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The giant garter snake is endemic to the Central Valley wetlands of California. It is active when water temperatures are at 20°C or more, and is dormant underground when its aquatic habitat is below this temperature. Fish and frogs form a large portion of the diet of the giant garter snake.

Destruction of wetland and habitat has been so widespread, this species is listed as threatened by the state and federal governments. The giant garter snake populations of the San Joaquin Valley are now tiny disconnected remnants. It has been extirpated from 98% of the former San Joaquin habitat. The giant garter snake has fared better in the Sacramento Valley because rice cultivation and the associated canals have provided habitat, when rice land is fallowed, populations seem to then move away from adjacent ditches.

In addition to habitat loss and fragmentation, introduced predators such as the American bullfrog may also be suppressing recovery. Attempts are underway to restore artificial wetlands to provide quality habitat for the giant garter snake, but it is too early to know if these efforts will significantly aid the recovery of this threatened species.
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Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) The range extends from coastal California in the vicinity of Salinas, Monterey County, south to the vicinity of El Rosario in northern Baja California and disjunctly south as isolated populations to the La Presa region of southern Baja California, at elevations from sea level to around 2,450 meters (8,000 feet) (McGuire and Grismer 1993, Jennings and Hayes 1994, Rossman et al. 1996, Grismer 2002, Stebbins 2003 ). See Ely (1992, Herpetol. Rev. 23:124-125) for recent records from Fresno County. less ↑

Thamnophis ordinoides or the Northwestern Garter snake, is a species of colubrid garter snake that lives in Oregon, Washington, California, and British Columbia. The garter snake is small, with adults averaging around 14-21 inches long. The northwestern garter snake is one of the most variable snakes in the world, however, no subspecies have been confirmed. The snake is most commonly found on the edge of meadows, surrounded by forest, as some sunshine is needed for their survival. less ↑

The San Francisco garter snake (Thamnophis sirtalis tetrataenia) is a slender multi-colored subspecies of the common garter snake. Designated as an endangered subspecies since the year 1967, it is endemic to San Mateo County and the extreme northern part of coastal Santa Cruz County in California. Some researchers estimate that there are only 1,000 to 2,000 adult snakes of the subspecies T. s. tetrataenia remaining. However, the full extent of the snakes' habitat has not been fully documented, and many snakes may utilize creeks and other waterways that are currently unexplored. This garter snake prefers wet and marshy areas, and because of its elusive nature, it is difficult to see or capture. less ↑