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A Guide to the Amphibians
and Reptiles of California


San Francisco Gartersnake -
Thamnophis sirtalis tetrataenia

(Cope, 1875)
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San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
  Adult, San Mateo County  
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Adult, San Mateo County Adult, San Mateo County
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Adult, San Mateo County Adult, San Mateo County
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Adult, San Mateo County Underside of adult, San Mateo County Adult, San Mateo County
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Pale-striped adult, San Mateo County
© Brian Hubbs
Pale-striped adult, San Mateo County
© Brian Hubbs
Adult, San Mateo County
© Brian Hubbs
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Adult, San Mateo County
© Brian Hubbs
Adult, San Mateo County
© Benjamin German
Adult, San Mateo County
© Benjamin German
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
Adult, San Mateo County © Ed Dickie Adult, San Mateo County © Jon Hirt
San Francisco Gartersnake San Francisco Gartersnake San Francisco Gartersnake
A pair of mating adults in early March, San Mateo County  © James Maughn
San Francisco Gartersnake San Francisco Gartersnake sign San Francisco Gartersnake stamp
Adult, San Mateo County
© Guntram Deichsel
San Mateo County Sign
© Brian Hubbs

1996 postage stamp from the Endangered Species series
Habitat
San Francisco Gartersnake Habitat San Francisco Gartersnake Habitat San Francisco Gartersnake Habitat
Habitat, San Mateo County Habitat, San Mateo County Habitat, San Mateo County
San Francisco Gartersnake Habitat San Francisco Gartersnake Habitat California Red-legged Frog Habitat
Habitat, San Mateo County Habitat, San Mateo County
© Guntram Deichsel
Habitat, San Mateo County

Description

Not Dangerous to 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
Adults of this species measure 18 - 55 inches in length (46 - 140 cm), but the average size is under 36 inches (91 cm).
Appearance
A medium-sized snake with a head barely wider than the neck and keeled dorsal scales. Robert Stebbins calls this snake "One of the most beautiful serpents in North America." A wide blue-green or greenish yellow dorsal stripe is bordered with black stripes. Below the black stripe is a continuous red stripe, bordered below by another black stripe. Below that is a bluish or greenish yellow lateral stripe. There may also be a thin line of black below the lateral stripe on the edge of the belly. The underside is bluish-green. Occasionally, the red stripes may be marked with black, similar to T. s. infernalis. The head is red, with eyes that are relatively larged compared with other gartersnake species.

Some average scale counts: 7, occasionally 8, rarely 6 or 9, upper labial scales, often with black wedges. 10 lower labial scales. The rear pair of chin shields are longer than the front. Average of 19 scales at mid-body.
Key to Identifying California Gartersnake Species
Behavior
Primarily active during daylight. A good swimmer. Often escapes into water when threatened. When first handled, typical of gartersnakes, this snake often releases cloacal contents and musk, and strikes. The species T. sirtalis is capable of activity at lower temperatures than other species of North American snake.
Diet
Eats a wide variety of prey, including amphibians and their larvae (the endangered California Red-legged Frog - Rana draytonii, is a main food source), fish, birds, and their eggs, small mammals, reptiles, earthworms, slugs, and leeches. This snake is able to eat adult Pacific newts (Taricha) which are deadly poisonous to most predators.
Reproduction
Mating occurs in the spring (and possibly the fall ) and young are born live, spring to fall.
Range
The species Thamnophis sirtalis - Common Gartersnake, has the largest distribution of any gartersnake, ranging from the east coast to the west coast and north into Canada, farther north than any other species of snake in North America.

This subspecies, Thamnophis sirtalis tetrataenia - San Francisco Gartersnake, is endemic to California, found only on the San Francisco peninsula from near the southern San Francisco County line south to Ano Nuevo in San Mateo County. (There is also a record from Rancho del Oso state park in Santa Cruz County.)
Habitat
Utilizes a wide variety of habitats, preferring grasslands or wetlands near ponds, marshes and sloughs. May overwinter in upland areas away from water. 

Stebbins (2003) lists the elevation record for the species (not specifically this subspecies) as 8,000 ft. (2,438 m).
Taxonomic Notes
In 1995, Doug Rossman and Jeff Boundy re-named the Thamnophis sirtalis found on the San Francisco Peninsula T. s. infernalis, (removing the name T. s. tetrataenia, but recognizing that the snakes were still subspecifically distinct), and lumped the coastal T. sirtalis with T. s. concinnus. This taxonomy is shown on the range map in the 1996 book, The Garter Snakes - Evolution and Ecology 1. In 1998, Sean Barry and Mark Jennings petitioned the International Commission on Zoological Nomenclature (ICZN) to restore the previous nomenclature 2. With no opposition from Boundy or Rossman, the ICZN agreed to restore the name T. s. tetrataenia to snakes on the San Francisco peninsula 3. Nevertheless, some authors either missed the restoration of this nomenclature or chose to ignore it, and their work still reflects Rossman and Boundy's previous nomenclature.

(Thanks to Sean Barry for this clarification)
Conservation Issues  (Conservation Status)
Listed as endangered by the state and by the federal government. The habitat of this snake has declined severely due to urban development and agricultural land use and altering of the waterways needed by this snake. These habitat changes have also reduced populations of one of this snake's main food sources, the California Red-legged Frog - Rana draytonii . Some authorities believe that the remaining fragmented populations of this snake could be further threatened by overcollecting for the pet trade. San Francisco Gartersnakes are popular pets in Europe, where it is possible that there are more of these snakes than there are in the wild in California.

Taxonomy
Family Colubridae Colubrids Oppel, 1811
Genus Thamnophis North American Gartersnakes Fitzinger, 1843
Species sirtalis Common Gartersnake (Linnaeus, 1758)
Subspecies


tetrataenia San Francisco Gartersnake (Cope, 1875)
Original Description
Thamnophis sirtalis - (Linnaeus, 1758) - Syst. Nat., 10th ed., Vol. 1, p. 222
Thamnophis sirtalis tetrataenia - (Cope, 1875) - in Yarrow, in Wheeler's Rep. Surv. W. 100th Mer., Vol. 5, Zool., p. 546

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
sirtalis
- sirtalis, like a garter - probably refers to the to striped pattern
tetrataenia - Greek - tetra - four, and Latin - taenia - stripes or bands, refers to the dorsal color areas

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Alternate Names
T. s. infernalis - see Taxonomic Notes above.
Eutaenia sirtalis tetrataenia

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. hammondii - Two-striped Gartersnake
T. m. marcianus - Marcy's Checkered Gartersnake
T. ordinoides - Northwestern Gartersnake
T. s. fitchi - Valley Gartersnake
T. s. infernalis - California Red-sided Gartersnake

More Information and References
California Department of Fish and Wildlife

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.

Thelander, C. G., ed. Life on the Edge: A Guide to California's Endangered Natural Resources Volume I: Wildlife.
Santa Cruz, California, Biosystems Books, 1994.

Don Roberson's Web Site

1 Rossman, Douglas A., Neil B, Ford, & Richard A. Siegel. The Garter Snakes - Evolution and Ecology. University of Oklahoma press, 1996.

2 Barry, Sean J., and Mark R. Jennings. 1998. Coluber infernalis Blainville 1835 and Eutaenia sirtalis tetrataenia Cope in Yarrow, 1875 (currently Thamnophis sirtalis infernalis and T. s. tetrataenia; Reptilia: Squamata): proposed conservation of the subspecific names by the designation of a neotype for T. s. infernalis. Bulletin of Zoological Nomenclature 55: 224-228.

3 CZN 2000. Opinion 1961. Coluber infernalis Blainville 1835 and Eutaenia sirtalis tetrataenia Cope in Yarrow, 1875 (currently Thamnophis sirtalis infernalis and T. s. tetrataenia; Reptilia: Squamata): conservation of the subspecific names by the designation of a neotype for T. s. infernalis. Bulletin of Zoological Nomenclature 57: 191-192.

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.



Organization
Status Listing
U.S. Endangered Species Act (ESA) FE - 3/11/67 Endangered
California Endangered Species Act (CESA) SE - 6/27/71 Endangered
California Department of Fish and Wildlife DFG:FP Fully Protected
Bureau of Land Management None
USDA Forest Service None

 

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