A Guide to the Amphibians
and Reptiles of California

Two-striped Gartersnake - Thamnophis hammondii

(Kennicott, 1860)

Click on a picture for a larger view

Range in California: Red

Key to Identifying
California Gartersnakes

Range Maps of
California Gartersnakes

Baja California

Sub-adult, San Diego County

Adult, striped morph, Santa Barbara County © Brian Hubbs

Sub-adult, San Diego County

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

Adult, San Diego County © Paul Maier

Adult, preparing to shed, coastal San Diego County

Adult, San Diego County © Taylor Henry

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

Adult, Ventura County © Jeremy Huff

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, San Bernardino County © Jeff Ahrens

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

Adult, Ventura County © Patrick Briggs

Adult, preparing to shed, with milky eyes,
San Diego County

Adult in creek, Orange County
© Jeff Ahrens

Adult swimming in a flooded meadow in in the San Diego County mountains
© Cherie Trivizo

Adult, Riverside County © Jeff Ahrens

Adult in creek, San Bernardino County © Jeff Ahrens

Adult in an Orange County creek © Robert Hamilton

The Two-striped Gartersnake typically has a single light stripe low on each side of the body but lacks the light stripe on top of the back which is present in most other gartersnakes found in California.

Sign, San Diego County park

Dark Morph and Melanistic Snakes

Melanistic adult, San Luis Obispo County © Katie Drexhage

Very dark adult, Monterey County © Harry Moffett

A very dark adult from the San Gabriel Mountains in San Bernardino County © Kyle Watson

Melanistic adult, San Luis Obispo County © Ryan Sikola

Two-striped Gartersnakes 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

Adult eating a sucker on a rock next to the San Gabriel River, Los Angeles County. © Seth Coffman

This juvenile snake is eating a Baja California Treefrog tadpole in the
Santa Monica Mountains of Los Angeles County. © NPS

This juvenile snake is eating a young California Treefrog in the Santa Monica Mountains of Los Angeles County. © NPS

Adult eating a trout pulled from a pool in a Monterey County creek that dried up during the summer of 2014 due to drought.
© Pete Veilleux

Habitat

Habitat, coastal sage,
San Diego County

Habitat, desert creek,
San Diego County

Habitat, flooded meadow in Spring, San Diego County mountains
© Cherie Trivizo

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, small creek, Orange County
© Jeff Ahrens

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

Habitat, mountain creek,
San Diego County

Habitat, seasonal pond,
San Diego County

Riparian habitat, Ventura County.
© Brian Hubbs

Habitat, small creek,
San Diego County

Short Video

A Two-striped Gartersnake
filmed in San Diego County.

Description

Not Dangerous (Non-poisonous) - This snake does not have venom that is dangerous to most humans.

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.

Color and Pattern

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.

Key to Identifying California Gartersnake Species

Life History and 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.

Defense

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

Diet and Feeding

Eats tadpoles, newt larvae, small frogs and toads, fish, and occasionally earthworms and fish eggs.

Garden Slender Salamanders - Batrachoseps major (and their detached tails) and aquatic leeches hava also been found in the stomach contents of T. hammondii. (Edward L. Irvin, et al. Herpetological Review 34)1), 2003.

Forages for food in and under water.

An adult T. hammondii was observed in an underwater ambush position about 15 cm below the surface, compressing its body into side-by-side loops while using its tail to anchor itself in stable aquatic vegetation. From this position it periodically quickly lunged forward at its prey. (Edward L. Ervin and Robert N. Fisher, Herpetological Revies 38(3), 2007.

Breeding

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

Habitat

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

Geographical 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 California in isolated areas.
Also occurs on Catalina Island.

Elevational Range

At elevations from sea Level to 6,988 ft. (2130 m).

Notes on Taxonomy

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.

Alternate and Previous Names (Synonyms)

Thamnophis hammondii - Two-striped Garter Snake (Stebbins 1985, 2003, 2012)
Thamnophis couchi hammondii - Two-striped Garter Snake (Stebbins 1966)
Thamnophis elegans hammondii (Stebbins 1954)
Thamnophis elegans hammondii - Southern California garter snake (Klauber 1934)
California garter snake (Van Denburgh 1897)
Thamnophis hammondii - (Kennicott, 1860)
Hammond's garter snake;
Pacific garter snake;
Water snake

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	Oppel, 1811
Genus	Thamnophis	North American Gartersnakes	Fitzinger, 1843
Species	hammondii	Two-striped Gartersnake	(Kennicott, 1860 )
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
California Department of Fish and Wildlife 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, 1957.

Conservation Status

The following status listings are copied from the April 2018 Special Animals List and the 2017 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife.

If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.

Check here to see the most current complete lists.

The 2017 Special Animals List lists the population on Santa Catalina Island as a separate subspecies, Thamnophis hammondii ssp. - Santa Catalina garternake. This listing for this snake is shown below.

This is the listing for Thamnophis hammondii - two-striped gartersnake:

Organization

Status Listing

NatureServe Global Ranking

Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.

NatureServe State Ranking

S3S4

Vulnerable—Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation from the state.

Apparently Secure—Uncommon but not rare in the state; some cause for long-term concern due to declines or other factors.

U.S. Endangered Species Act (ESA)

None

California Endangered Species Act (CESA)

None

California Department of Fish and Wildlife

SSC

Species of Special Concern

Bureau of Land Management

Sensitive

USDA Forest Service

Sensitive

IUCN

Least Concern

This is the listing for Thamnophis hammondii ssp. - Santa Catalina garternake:
Organization	Status Listing
NatureServe Global Ranking	G4T1	The species is: Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors. This subspecies is: Critically Imperiled—At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors. Imperiled—At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.
NatureServe State Ranking	S1	Critically imperiled in the state because of extreme rarity (often 5 or fewer populations) orbecause of factor(s) such as very steep declines making it especially vulnerable to extirpation from the state.
U.S. Endangered Species Act (ESA)	None
California Endangered Species Act (CESA)	None
California Department of Fish and Wildlife	None
Bureau of Land Management	None
USDA Forest Service	None
IUCN	Not Listed

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