A Guide to the Amphibians
and Reptiles of California

Thamnophis hammondii - Two-striped Gartersnake

Click on a picture for a larger view

Range in California: Red

Key to identifying
California gartersnakes

Range maps of
California gartersnakes

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Sub-adult, San Diego County

Adult, San Diego County © Taylor Henry

Adult, preparing to shed, coastal San Diego County

Sub-adult, spotted morph, Cottonwood Creek, San Diego County

Adult, striped morph, Santa Barbara County © Brian Hubbs

Adult, spotted morph (with faint stripes), Laguna Mountains,
San Diego County © John Stoklosa

Sub-adults, two color phases,
Ventura County. © Brian Hubbs

Adult, Santa Barbara County
© Jason Butler

An adult snake with a reddish stripe from just west of the Piru River in Ventura County. © Vince Semonsen

Adult, Ventura County © Jeremy Huff

Adult from the Mohave Desert at Victorville,
San Bernardino County © Michael Clarkson

Adult, Ventura County © Patrick Briggs

Dark morph snake, with no stripes or spots,
San Luis Obispo County © Katie Drexhage

Adult, preparing to shed,
San Diego County

This snake typically has a single light stripe low on each side.

Sign, San Diego County park

Feeding

Steve Ivie and his Cub Scout troupe saw this snake enter a river in the San Gabriel Mountains of Los Angeles County. They watched the snake swim upstream and grab a trout about 8 or 9 inches in length, then drag the trout onto a rock at the edge of the river, and eat it, as you can see above. © Steve Ivie

Habitat

Habitat, coastal sage,
San Diego County

Habitat, desert creek,
San Diego County

Habitat, San Diego County
mountain meadow

Habitat, coastal stream,
San Diego County

Habitat, San Gabriel Mountains,
Los Angeles County

Habitat, creek, 5,200 ft., San Gabriel Mountains, Los Angeles County

Habitat, lake edge, 4,600 ft.
San Diego County

Habitat, mountain creek,
San Diego County

Habitat, seasonal pond,
San Diego County

Short Video

A Two-striped Gartersnake
filmed in San Diego County.

Description

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.

Taxonomy
Family	Colubridae	Colubrids
Genus	Thamnophis	North American Gartersnakes
Species	hammondii	Two-striped Gartersnake
Original Description
Thamnophis hammondii - (Kennicott, 1860) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 12, p. 332 from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
Meaning of the Scientific Name
Thamnophis - Greek - thamnos - shrub or bush, and ophis - snake, serpent hammondii - honors Hammond, William A. from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Alternate Names
None
Other California Gartersnakes
T. a. atratus - Santa Cruz Gartersnake T. a. hydrophilus - Oregon Gartersnake T. a. zaxanthus - Diablo Range Gartersnake T. couchii - Sierra Gartersnake T. gigas - Giant Gartersnake T. e. elegans - Mountain Gartersnake T. e. terrestris - Coast Gartersnake T. e. vagrans - Wandering Gartersnake T. m. marcianus - Marcy's Checkered Gartersnake T. ordinoides - Northwestern Gartersnake T. s. fitchi - Valley Gartersnake T. s. infernalis - California Red-sided Gartersnake T. s. tetrataenia - San Francisco Gartersnake
More Information and References
Natureserve Explorer California Dept. of Fish and Game Rossman, Douglas A., Neil B, Ford, & Richard A. Siegel. The Garter Snakes - Evolution and Ecology. University of Oklahoma press, 1996. Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012. Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972. Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003. Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992. Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998. Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009. Bartlett, R. D. & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000. Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997. Ernst, Carl H., Evelyn M. Ernst, & Robert M. Corker. Snakes of the United States and Canada. Smithsonian Institution Press, 2003. Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press.

Conservation Status
The following status listings come from the Special Animals List which is published by the California Department of Fish and Wildlife. The Special Animals List lists the population on Santa Catalina Island as a separate unnamed subspecies, the Santa Catalina Garter Snake The listings for this species are recorded below in red.
Organization	Status Listing
U.S. Endangered Species Act (ESA)	None None
California Endangered Species Act (CESA)	None None
California Department of Fish and Wildlife	DFG:SSC None	California Species of Special Concern
Bureau of Land Management	BLM: NoneS	Sensitive
USDA Forest Service	USFS:S None	Sensitive
Natureserve Global Conservation Status Ranks	G3 S2 G3T1? S1	Vulnerable Vulnerable
World Conservation Union - IUCN Red List	IUCN:L None C	Least Concern

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