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A Guide to the Amphibians
and Reptiles of California


Two-striped Gartersnake - Thamnophis hammondii

(Kennicott, 1860)
Click on a picture for a larger view



Two-striped Gartersnake Range Map
Range in California: Red

observation link





Two-striped Gartersnake
Sub-adult, San Diego County
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
  Sub-adult, San Diego County  
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Sub-adult, San Diego County Adult, San Diego County © Taylor Henry
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Adult, preparing to shed, coastal San Diego County
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Sub-adult, spotted morph, Cottonwood Creek, San Diego County Adult, striped morph, Santa Barbara County © Brian Hubbs
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnakes
Adult, spotted morph (with faint stripes), Laguna Mountains,
San Diego County © John Stoklosa
Sub-adults, two color phases,
Ventura County. © Brian Hubbs
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
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
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Adult from the Mohave Desert at Victorville,
San Bernardino County © Michael Clarkson
Adult, Ventura County © Patrick Briggs
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Adult, preparing to shed, with milky eyes,
San Diego County
Adult, San Bernardino County © Jeff Ahrens
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Adult in creek, Orange County
© Jeff Ahrens
Adult in creek, Orange County
© Jeff Ahrens
Adult, Riverside County © Jeff Ahrens
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Adult in creek, San Bernardino County © Jeff Ahrens A very dark adult from the San Gabriel Mountains in San Bernardino County © Kyle Watson
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Dark morph snake, (melanistic) with no stripes or spots,
San Luis Obispo County © Katie Drexhage
The Two-striped Gartersnake typically has a single light stripe low on each side.
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake Sign
Adult in an Orange County creek  © Robert Hamilton Sign, San Diego County park
     
Feeding
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
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
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
Two-striped Gartersnake Two-striped Gartersnake Two-striped Gartersnake
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
Coast Gartersnake Coast Gartersnake Two-striped Gartersnake
This juvenile snake is eating a Baja California Treefrog tadpole in the
Santa Monica Mountains of Los Angeles County. © NPS
Adult eating a sucker on a rock next to the San Gabriel River, Los Angeles County. © Seth Coffman
Coast Gartersnake Coast Gartersnake  
This juvenile snake is eating a young California Treefrog in the Santa Monica Mountains of Los Angeles County. © NPS  
     
Habitat
Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat
Two-striped Gartersnake Habitat
Habitat, coastal sage,
San Diego County
Habitat, desert creek,
San Diego County
Habitat, San Diego County
mountain meadow
Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat
Habitat, coastal stream,
San Diego County
Habitat, San Gabriel Mountains,
Los Angeles County
Habitat, creek, 5,200 ft., San Gabriel Mountains, Los Angeles County
Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat
Habitat, lake edge, 4,600 ft.
San Diego County
Habitat, mountain creek,
San Diego County
Riparian habitat, Ventura County.
© Brian Hubbs
Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat Two-striped Gartersnake Habitat
Habitat, small creek,
San Diego County
Habitat, seasonal pond,
San Diego County
Habitat, small creek, Orange County
© Jeff Ahrens
     
Short Video
  Two-striped Gartersnake  
  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.

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.
Full Species Range Map
Elevational Range
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.

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 come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


The 2015 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.
Organization
Status Listing
NatureServe Global Ranking G4
NatureServe State Ranking S3S4
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 S Sensitive
USDA Forest Service S Sensitive
IUCN LC Least Concern
The Special Animals List listing of the Catalina Island subspecies:

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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