Thamnophis hammondii - Two-striped 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

24 - 40 inches long (61 - 102 cm). Most often 18 - 30 inches long (46 - 76 cm). Neonates are 7.5 - 9 inches (19 - 23 cm).

Appearance

A medium-sized snake with a head barely wider than the neck and keeled dorsal scales. Appearance is variable - there are two basic pattern morphs. Both have a drab olive, brown, or dark gray ground color, with no dorsal stripe, except for a spot on the neck. The striped morph has a yellowish to gray lateral stripe on each side, and a fairly uniform dorsal coloring, with only faint spotting. The unstriped morph lacks the lateral stripes and has two rows of small dark spots on each side. Light areas between the scales between these spots can create a checkered appearance (as seen in some of the pictures above.) The underside is pale yellow or orange, unmarked, or with dark smudging.

A dark morph is found along the outer coast in San Luis Obispo County. A dark green and a reddish color morph occur along the Piru River in Ventura County. A melanistic population occurs on Catalina Island.

Behavior

Primarily aquatic. Diurnal. Also active at night and at dusk during hot weather in some areas. Can be active from January to November depending on weather conditions.

Most gartersnakes, when picked up, will often strike repeatedly and release cloacal contents and musk.

Diet

Eats tadpoles, newt larvae, small frogs and toads, fish, and occasionally worms and fish eggs. Probably forages for food in and under water.

Reproduction

Breeding has been observed in late March and early April, with live young born in late July and August.

Range

Ranges continuously from near Salinas in Monterey County south along the coast mostly west of the south Coast Ranges, to southern California where it ranges east through the Transverse Ranges (and into the desert in Victorville) and south through the Peninsular Ranges into northern Baja California. Occurs in southern Baja in isolated areas. Also occurs on Catalina Island. At elevations from sea Level to 6,988 ft. (2130 m).

Habitat

Generally found around pools, creeks, cattle tanks, and other water sources, often in rocky areas, in oak woodland, chaparral, brushland, and coniferous forest.

Taxonomic Notes

Formerly classified as a subspecies of Thamnophis couchii. T. digueti was synonymized with T. hammondii by McGuire and Grismer (1993, Herpetologica 49:354-365).

The Santa Catalina population of T. hammondii is treated as a distinct subspecies by the California Dept. of Fish and Game - Santa Catalina garter snake, Thamnophis hammondii ssp.

Conservation Issues (Conservation Status)

Protected by the state. Loss of wetland habitats have contributed to a reduction in the range of this snake.

The California Dept. of Fish and Game lists the Santa Catalina garter snake, Thamnophis hammondii ssp. - as a California Species of Special Concern.