Western Terrestrial Garter Snake (California Garter Snakes)

Western Terrestrial Garter Snake

Thamnophis elegans

Description ⁴

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.

Identification ⁵

If you're into counting labial scales these guys usually have 8. Usually. They can look quite similar to Red-headed and San Francisco Garter Snakes when red, but they never have red on the head. When they have no red they can look very, very similar to T. atratus, but in T. atratus look for

acute internasal scales vs. blunt in T. elegans
lemon yellow throat coloration

Habitat ⁶

Comments: This species occurs in a wide variety of habitats, from lowlands to high mountains: grassland, shrubland, woodland, and open areas in forests. It is chiefly terrestrial in most areas, but also aquatic in some locations (e.g., high Sierra Nevada). Often it inhabits wetlands and areas near streams, ponds, and lakes.

Trophic strategy ⁷

Comments: Feeds on slugs, worms, snails, leeches, tadpoles, frogs, fish, mice, and occasionally small birds. Also eats insects, and carrion. Some forms capture prey in water, others feed entirely terrestrially (Nussbaum et al. 1983). Depends on amphibians in the high Sierra Nevada, California (Jennings et al. 1992).

At least in some parts of the range of this snake, the rear upper jaw teeth are relatively long and bladelike and apparently function in impaling, holding, and manipulating the prey. The snakes salivary secretions aid in breaking down prey tissues.

Reproduction ⁸

Courtship and mating occur primarily in spring, soon after emergence from hibernation, though late summer sexual activity has been observed in some parts of the range. In the mountains, newborn individuals first appear most often in August and early September; at lower elevations births sometimes occurs as early as mid-July. Litter size usually is fewer than 20.

Taxonomy ⁹

Comments: The systematic relationships among the subspecies of THAMNOPHIS ELEGANS and between T. ELEGANS and T. COUCHI need further investigation (Nussbaum et al. 1983).

Tanner and Lowe (1989) examined snakes from a small part of the range of subspecies VAGRANS and proposed two new subspecies, ARIZONAE from the Little Colorado River basin of Arizona and New Mexico and VASCOTANNERI from the Upper Colorado River basin of Utah; these taxa were distinguished only by coloration characteristics that in fact occur in several other geographic areas within the range of subspecies VAGRANS (e.g., Colorado, Hammerson 1999). Until a thorough study of variation is completed, these newly described subspecies should be regarded as dubious (Hammerson 1999).

Cytochrome b phylogeny does not match the current subspecific classification of T. ELEGANS (Bronikowski and Arnold 2001). A range-wide assessment of genetic and morphological variation is needed.

Sources and Credits

More Info

Range Map

iNat Map

Region	Bay Area, Northern CA, Sierra Nevada, Southern CA

‹ › ×