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A Guide to the Amphibians
and Reptiles of California


California Red-sided Gartersnake -
Thamnophis sirtalis infernalis

(Blainville, 1835)
Click on a picture for a larger view



Common Gartersnakes California Range Map
Range in California: Red and
Purple: South Coast Gartersnake

Click the map for a guide
to the other subspecies.


observation link



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California Red-sided Gartersnake
Adult, Monterey County
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
  Adult with blue coloring, Marin County  
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
  Adult with blue coloring, Marin County  
California Red-sided Gartersnake California Red-sided Gartersnake
California Red-sided Gartersnake
Large adult, Monterey County. Photos © Gary Nafis. Specimen courtesy of David Keegan & Susan Whitford of the Santa Lucia Conservancy. Adult, Solano County, © Rick Staub
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
Adult, Humboldt County
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
Adult, Humboldt County Adult, Santa Cruz County © John Sullivan
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
Adult, Contra Costa County Adult, Fort Ord, Monterey County © K. Moussally
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
Adult, Mendocino County
© Mike Spencer
Adult, Sonoma County
© Suzanne Kennedy
Adult, Santa Clara County © Holly Lane
This snake was found sitting on a trail with its head elevated, eyeing a California Kingsnake that was approaching it from some tall grass. Kingsnakes eat other snakes, and it looked like this gartersnake knew it.
California Red-sided Gartersnake California Red-sided Gartersnake California Red-sided Gartersnake
Adult, Alameda County © David Rodriguez Adult, Alameda County
© David Rodriguez
Valley Gartersnake California Red-sided Gartersnake Puget Sound Gartersnake
Juvenile, coastal San Luis Obispo County, just north of Santa Barbara County line within the accepted range for T. s. infernalis, showing the dark head and small red blotches charactistic of the subspecies T. s. fitchi.

Adult, with blue stripes, Sonoma County, near Sebastopol. © Nancy Mittasch

Comparing the top of the heads can help to identify these sympatric species on the north coast:
Left: T. sirtalis (Puget Sound Gartersnake)
Right: T. ordinoides - Northwestern Gartersnake
© Filip Tkaczyk
     
South Coast Gartersnake
California Red-sided Gartersnake California Red-sided Gartersnake  
Adult, (South Coast Gartersnake), Riverside County © Brian Hinds  
   
Habitat
California Red-sided Gartersnake Habitat California Red-sided Gartersnake Habitat California Red-sided Gartersnake Habitat
Habitat, Alameda County Habitat, (winter) Monterey County.
California Red-sided Gartersnake Habitat California Red-sided Gartersnake Habitat California Red-sided Gartersnake Habitat
Habitat, Marin County
Historical habitat of the South Coast form, San Diego County
Habitat, Marin County
California Red-sided Gartersnake Habitat    
Habitat, Humboldt County    
     
Short Videos
California Red-sided Gartersnake California Red-sided Gartersnake  
A red-sided gartersnake swims around in a small cattle pond on a sunny spring afternoon in Alameda County. I wanted to get a closer look, so I walked over to the snake's side of the pond, but then it swam to the other side, again and again, until I got tired of going round in circles. A huge feisty Red-sided Gartersnake from Santa Barbara County strikes out a few times at its captor.
Video © Vince Semonsen


 
   
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
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.
The eyes 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.
Color and Pattern
Ground color is dark olive to black.
The dorsal stripe is wide and well-defined, and yellowish to bluish in color.
Light stripes along the lower sides are not very distinct, often blending in with the color of the belly.
There are red bars alternating with the ground color along the sides above the lateral stripes.
The head is red or orangish.
The underside is bluish gray, sometimes very blue north of the Bay Area (shown above) and may have some dark coloring.
Key to Identifying California Gartersnake Species

Life History and Behavior

Activity
Primarily active during daylight.
A good swimmer.
The species T. sirtalis is capable of activity at lower temperatures than other species of North American snake.
Defense
Often escapes into water when threatened.
When first handled, typical of gartersnakes, this snake often releases cloacal contents and musk, and strikes.
Diet and Feeding
Eats a wide variety of prey, including amphibians and their larvae, 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.
Breeding
Mating occurs in the spring (and possibly the fall ) and young are born live, spring to fall.

Geographical 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 infernalis - California Red-sided Gartersnake, is endemic to California, ranging from Humboldt County south, along the coast ranges (excluding much of the San Francisco peninsula) and east of the San Francisco Bay along the central and south coasts to San Diego County. (Snakes from the Santa Clara River area in Ventura County south, may prove to be a new species [Stebbins 2003]). I have followed the California Dept. of Fish and Wildlife's designation of these south coast snakes by indicating them separatly on the map, but grouping then with T. s. infernalis until more research proves otherwise.

Rossman et al. in The Garter Snakes - Evolution and Ecology 1996 * show T. s. fitchi ranging along the central coast from south of Monterey Bay to Santa Barbara County. Robert Stebbins, in his 2003 western field guide, shows T. s. infernalis along the central coast with an intergrade zone around Ventura County. I have chosen to show T. s. infernalis ranging along the south coast with no intergrade zone, after personal commications that told me the T. sirtalis in that area show characteristics of T. s. fitchi, but are still T. s. infernalis, however I remain skeptical and wait for more information.
Elevational Range
Rossman et al (1996) show the elevation record for the species (not specifically this subspecies) at 8,333 feet (2540 m.). Stebbins (2003) shows it as 8,000 ft. (2,438 m).

Habitat
Utilizes a wide variety of habitats - forests, mixed woodlands, grassland, chaparral, farmlands, often near ponds, marshes, or streams. 

Notes on Taxonomy

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 nomenclature.

(Thanks to Sean Barry for this information.)


The South Coast Gartersnake

Southern California Common Garter Snakes have been treated as a unique taxon - Thamnophis sirtalis ssp. - South Coast Gartersnake, but the recognition of this subspecies is rare. The only published description I can find is in the following paper:

Jennings, Mark R. and Marc P. Hayes. Amphibian and Reptile Species of Special Concern in California. California Department of Fish and Game, published November 1, 1994.

The information about this snake that was published in the paper can be found on the California Dept. of Fish and Game website.

Jennings and Hayes state that this snake is known from scattered localities from the Santa Clara River Valley in Ventura County south to the vicinity of San Pasqual in San Diego County. It is restricted to marsh and upland habitats near permanent water with good strips of riparian vegetation where adequate prey and refuge can be found.
Conservation Issues  (Conservation Status)
None for the northern population.

The California Department of Fish and Game lists the South Coast Gartersnake as a California Species of Special Concern. Jennings and Hayes (in the 1994 paper cited above) state that 75 percent of the known historic localities for this snake no longer support snakes due to habitat loss from urbanization and flood control projects, floods, extended droughts, and introduced aquatic predators.
Taxonomy
Family Colubridae Colubrids Oppel, 1811
Genus Thamnophis North American Gartersnakes Fitzinger, 1843
Species sirtalis Common Gartersnake (Linnaeus, 1758)
Subspecies

infernalis Red-sided Gartersnake (Blainville, 1835)
Original Description
Thamnophis sirtalis - (Linnaeus, 1758) - Syst. Nat., 10th ed., Vol. 1, p. 222
Thamnophis sirtalis infernalis - (Blainville, 1835) - Nouv. Ann. Mus. Hist. Nat. Paris, Vol. 4, p. 291, pl. 26, fig. 3

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
infernalis - Latin - of hell

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

Alternate Names
Boundy and Rossman classify T. s tetrataeia as T. s. infernalis with T. s. infernalis becoming T. s. concinnus.

Other California Garternakes
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. 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.


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.


This subspecies is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California, but populations along the coastal plain from Ventura County to San Diego County are listed as a separate subspecies by the Special Animals List - T. sirtalis ssp. - the South Coast Garter Snake (Coastal plain from Ventura Co. to San Diego Co., from sea level to about 850 m) and a California Species of Special Concern.
Organization
Status Listing
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife SSC California Species of Special Concern
Bureau of Land Management None
USDA Forest Service None

 

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