A Guide to the Amphibians
and Reptiles of California

Western Terrestrial Gartersnake - Thamnophis elegans

Coast Gartersnake - Thamnophis elegans terrestris

Fox, 1951

Click on a picture for a larger view

Purple: Range of this subspecies in California
Thamnophis elegans terrestris - Coast Gartersnake

Range of other subspecies in California:

Red: Thamnophis elegans elegans - Mountain Gartersnake

Dark Blue: Thamnophis elegans vagrans -
Wandering Gartersnake

Gray: General area of intergradation

Click on the map for a topographical view

Map with California County Names

Key to Identifying
California Gartersnakes

Range Maps of
California Gartersnakes

These are all Coast Gartersnakes but because the subspecies is so variable in appearance I have separated the pictures into four sections - three loosely-defined color and pattern types of adults, plus juveniles.

Coast Gartersnakes with Light Dorsal and Side Stripes and Black and Red Sides

Adult, Napa County

Adult, San Mateo County

Adult, Monterey County

Adult, Marin County

Adult, bulging from a recent meal,
Marin County

Adult, Marin County (San Rafael)

Adult, Humboldt County

Large old adult, San Mateo County

A Coast Gartersnake (right) basks in dry grass next to a San Francisco Gartersnake (left) that is emerging from a gopher hole in San Mateo County.
© Zach Lim

Adult, San Francisco County © Zach Lim

Adult, Del Norte County © Alan D. Barron

Adult, San Francisco County © Zach Lim

Adult, southern Napa County.

Adult, San Francisco County
© Luke Talltree

Adult with only a little red on sides, Sonoma County © Jim Tracy

Adult, Marin County

Adult, Marin County
© Yuval Helfman

Adult, San Mateo County
© Yuval Helfman

Adult, San Mateo County
© Faris K

This picture shows some of the variety of colors and patterns seen in a single population of this snake. All three snakes were all found at the same location in San Mateo County. © John Worden

Coast Gartersnakes with a Lot of Red on the Side Stripes

These are sometimes called "high red" or "flame" phase Coast Gartersnakes.

Adult with mostly red side stripes, San Mateo County © James Maughn

Juvenile, Alameda County

Adult, Contra Costa County

Adult, Monterey County

Wide red-striped adult, Santa Cruz County. © Susannah Goldston

Adult, Monterey County

Adult, Santa Cruz County
© Benjamin German

Adult, Humboldt County

Adult, Santa Cruz County © Zach Lim

Adult, Santa Cruz County
© 2005 Brad Alexander

Adult, Marin County (San Rafael)

This adult from Santa Clara County has red on all three stripes. © Holly Brown

Adult, San Mateo County © Jared Heald

Adults, San Mateo County
© Jared Heald

Adult, San Mateo County © Jared Heald

Adult, Alameda County © Jim Tracy

Adult and juvenile found in a city park in Lodi, San Joaquin County. © Patrick Briggs
(Somebody most likely transported the adult snake there since that is the range of the Mountain Gartersnake.)

Adults, San Mateo County © Faris K

Adult, San Mateo County
© Luke Talltree

This high red snake was found near the bay in Monterey County. © Phil Gervato

Red-striped adult, San Mateo County
© Brian Hubbs

Coast Garternakes with Little or No Red Coloring

Adult, with no red,
San Luis Obispo County

Adult, Humboldt County

Adult, San Luis Obispo County
© Patrick Briggs

Adult, Humboldt County

Adult, Del Norte County © Alan D. Barron

Adult, Monterey County.
© Van Wishingrad

Swimming adult, Monterey County.
© Van Wishingrad

A dark, bluish adult with only a few red spots from Santa Cruz County.
© James Maughn

Adult with little red, Marin County
© Luke Talltree

Adult, Sonoma County © Jim Tracy

Grayish adult, Marin County
© Jim Tracy

Adult puffed up in a defensive pose, with head flattened into a triangular shape, Santa Barbara County
@ Jeff Hopkins.

Brown phase adult, Santa Clara County, from a location where this phase is very common. © Faris K

Black phase adult, Santa Clara County, from the same location as the brown phase to the left. © Faris K

Juvenile Coast Gartersnakes

Juvenile, Marin County

Juveniles found under the same board in Alameda
County, with two different color patterns.

Juvenile, San Mateo County © Zach Lim

Juvenile, Del Norte County © Alan D. Barron

Comparisons With Sympatric Gartersnakes

Three species of gartersnakes found at the same Marin County location:
Right - Thamnophis atratus
Bottom left - Thamnophis sirtalis
Top - Thamnophis elegans
© Luke Talltree

Three species of gartersnakes found at the same Marin County location:
Top - Thamnophis sirtalis
Middle - Thamnophis elegans
Bottom - Thamnophis atratus
© Zach Lim

Two Marin County snakes:
Coast Gartersnake on top;
Aquatic Gartersnake on bottom.

Two Marin County snakes:
Aquatic Gartersnake on left;
Coast Gartersnake on right.

Coast Gartersnakes Feeding

A Coast Gartersnake eating a Spotted Towhee in Santa Cruz County.
The bird looks too big for the snake to swallow, but the final outcome is unknown © Scott Peden

Adult, San Mateo County, eating a bird,
found by Zach Mumbach,
Photo © Aaron Reif

Adult gartersnake of undetermined species eating a banana slug in Mendocino County. (It's either a Coast Gartersnake or an Oregon Gartersnake.)
© Gail Jackson

Adult eating a saltwater fish it found stranded in a tide pool on a rocky beach below the high tide mark in San Luis Obispo County © Randy Pickard

Adult eating a toxic California Newt in San Luis Obispo County © Ryan Sikola
You can read about gartersnakes eating toxic newts below.

Habitat

Coastal habitat,
Monterey County

Habitat, San Luis Obispo County

Coastal pond habitat,
San Mateo County

Riparian woodland habitat,
Contra Costa County

Coastal riparian habitat, Marin County

Forest habitat, Humboldt County

Coastal meadow habitat,
Humboldt County

Habitat, Alameda County

Coastal pond habitat,
San Mateo County

Coastal habitat, Monterey County

Short Video

A couple of snakes from the coast of Marin County, doing what snakes do -
trying to get away from an annoying human with a video camera. They finally did.

Description

Not Dangerous (Non-poisonous) - Garter snakes produce a mild venom which can be deadly to small prey but is not considered dangerous to most humans.

Size

Thamnophis elegans measures 18 - 43 inches in length (46 - 109 cm).

Appearance

A medium-sized slender snake with a head barely wider than the neck and keeled dorsal scales.
Some scale averages:
Average of 8 upper labial scales, occasionally 7, scales 6 and 7 are enlarged, higher than wide.
Average of 10 lower labial scales.
The front and rear pair of chin shields are equal in length.
The internasals are wider than long and not pointed in front.
Average scale count at mid-body is 21, rarely 19.

Color and Pattern

Color and pattern is highly variable, but there is usually a yellow dorsal stripe and a yellowish stripe along the bottom of each side.
The underside is yellowish to bluish-gray with varying amounts of reddish markings.

One color phase consists of a yellow dorsal stripe and two distinct yellowish or whitish side stripes, with black checkered spots on the sides inbetween the stripes on a reddish ground color, creating a red and black checkerboard appearance.
This phase occurs primarily on the San Francisco peninsula and north along the coast into Marin County and possibly farther.

On some snakes in the Santa Cruz Mountains and the Monterey Bay area, the side stripes are red, with varying degrees of checkering or barring of the black on a reddish ground color.

On some snakes the ground color is almost completely solid dark, the dorsal stripe is yellow, but the side stripes are reddish. We include pictures here of this phase from the East Bay hills, the Santa Cruz Mountains, and southeast Marin County near the S.F. bay.

Another color phase consists of almost completely solid dark coloring between distinct light side and dorsal stripes, with little or no red.
This phase is common on juveniles and seems to be most common on adults from Santa Cruz County south.

Along the far north coast in Humboldt and Del Norte Counties, the dark coloring can be light brown with little red, or there can be a heavy red wash over the sides.
Snakes there can also have three yellowish stripes, a reddish ground color with some black markings, and a dark bar beneath each side of the dorsal stripe.

Key to Identifying California Gartersnake Species

Life History and Behavior

Activity

Active in daylight.
Chiefly terrestrial - not as dependant on water as other gartersnake species, but more likely to be found near water.

Defense

When frightened, this species will sometimes seek refuge in vegetation or ground cover, but it will also crawl quickly into water and swim away from trouble.
If frightened when picked up, this snake will often strike repeatedly and release cloacal contents and musk.

Diet and Feeding

Western Terrestrial Gartersnakes - Thamnophis elegans - eat a wide range of prey (among the widest of any snake species - Rossmann, et al. 1996.) The prey depends on the size of the snake (large snakes tend to eat larger prey, small snakes can only eat smaller prey) and what prey is available. Populations found on the humid North Coast where slugs are abundant are genetically predisposed to eat slugs, while populations in dryer areas where slugs are less common refuse to eat slugs when they are offered. (Rossmann, et al. 1996.)

Diet includes: invertebrates such as slugs, leeches, snails, and earthworms; fish; amphibians - tadpoles, frogs, (and probably salamanders); snakes and lizards; birds; and small mammals such as mice and voles.

Toxic Newts

Thamnophis elegans terrestris has been found eating Taricha torosa, which are deadly poisonous to most predators, in San Luis Obispo County.
(Feldman, Hansen, & Sikola. Herpetological Review 51[3] 2020.)

There is evidence * that when Common Gartersnakes (Thamnophis sirtalis) eat Rough-skinned Newts (Taricha granulosa) they retain the deadly neurotoxin found in the skin of the newts called tetrodotoxin for several weeks, making the snakes poisonous (not venomous) to predators (such as birds or mammals) that eat the snakes. Since California Newts (Taricha torosa) also contain tetrodotoxin in their skin, and since gartersnake species other than T. sirtalis also eat newts, it is not unreasonable to conclude that any gartersnake that eats either species of newt is poisonous to predators.

* (Williams, Becky L.; Brodie, Edmund D. Jr.; Brodie, Edmund D. III (2004). "A Resistant Predator and Its Toxic Prey: Persistence of Newt Toxin Leads to Poisonous (Not Venomous) Snakes." Journal of Chemical Ecology. 30 (10): 1901–1919.) https://doi.org/10.1023/B:JOEC.0000045585.77875.09

Joseph Grinnell and Charles Lewis Camp. A Distributional List of the Amphibians and Reptiles of California. University of California Publications in Zoology Vol. 17, No. 10, pp. 127-208. July 11, 1917.

Reproduction

Mates primarily in spring.
Females are ovoviviparous - they carry the eggs internally until the young are born live from July to Sepember.

Habitat

Inhabits mixed woodland, grassland, coniferous forest, dunes, brushland, generally in the vicinity of ponds or flowing water.

Geographical Range

The species Thamnophis elegans - Western Terrestrial Gartersnake, ranges widely from the California coast north through most of northern California, Oregon, Washington, Idaho and Montana, into Canada, including Vancouver Island, British Columbia, Alberta and Saskatchewan, and east into the states of Wyoming, Colorado, Utah, Arizona and New Mexico and just barely making it into South Dakota, Nebraska, and Oklahoma. Many isolated populations exist, including those in the San Bernardino Mountains and one in Baja California Norte, Mexico (the San Pedro Martir Gartersnake.)

This subspecies, Thamnophis elegans terrestris - Coast Gartersnake, occurs along the Pacific coast from southern Oregon to Ventura County.

Most range maps showing subspecies of T. elegans, show T. e. elegans occurring in the Central Valley near Lodi. Previously I changed my range map to show a small population of T. e. terrestris there based on pictures of a bright red snake found in Lodi, but discussions with a herpetologist familiar with that area have convinced me that only T. e. elegans is found in the San Joaquin Valley. It's likely that the wild-caught Lodi specimen was transported there by somebody.

A range of intergradation is traditionally shown running the length of the Sierra Nevada mountains, but I am not certain exactly where or how wide it is.

Elevational Range

The species Thamnophis elegans - Western Terrestrial Gartersnake, occurs from sea level to 13,100 ft. (3,990 m) in elevation in Colorado. (Stebbins, 2003)

Notes on Taxonomy

T. e. vagrans intergrades with T. e. elegans in northeast California in Modoc and eastern Siskiyou counties and in south central Oregon (this snake was formerly classified as the subspecies Thamnophis elegans biscutatus - Klamath Gartersnake. Intergrades with T. e. elegans also occur along the southern and southeastern edge of the Sierras.

Three subspecies of Thamnophis elegans are found in California - T. e. vagrans - Wandering Gartersnake, T. e. e.egans - Mountain Gartersnake, and T. e. terrestris - Coast Gartersnake.

Rossman, Ford, and Seigel (1996) emphasize that a detailed study of geographic variation throughout the range of Thamnophis elegans is badly needed.

Bronikowski and Arnold (2001, Copeia 2001:508-513) found several clades within T. elegans that do not always follow the subspecies boundaries, and concluded that there was no support for the race terrestris. Presumably, the former T. e. terrestris snakes become T. e. elegans.

Hammerson (1999, Amphibians and Reptiles of Colorado. 2nd ed. Univ. of Colorado Press) synonymized T. e. arizonae and T. e. vascotanneri but retained three subspecies, T. e. vagrans, T. e. elegans, and T. e. terrestris.

Alternate and Previous Names (Synonyms)

Thamnophis elegans terrestris - Coast Garter Snake (Stebbins 1966, 1985, 2003, Stebbins & McGinnis 2012)
Thamnophis elegans hueyi (Stebbins 1954)
Thamnophis elegans terrestris - Coastal California garter snake (Fox 1951)
Thamnophis ordinoides elegans - Elegant Garter Snake (Eutainia elegans; Eutainia vagrans; Eutaenia infernalis, part; Eutaenia elegans lineolata; Eutaenia elegans brunnea; Eutaenia couchii; Thamnopis infernalis, part; Tropidonotus tri-vittatus; Eutaenia elegans couchii, part; Tropidonotus ordinatus infernalis; Tropidonotus ordinatus ver. couchii; Thamnophis vagrans; Thamnophis parietalis, part; Eutaenia elegans vagrans; Eutaenia hammondi, part; Thamnophis elegans, part; Eutaenia elegans infernalis. Boyd's Garter Snake; Pacific Garter Snake; Wandering Garter Snake; Hammond's Garter Snake; Single-striped Garter Snake; Green Garter Snake;, Western Garter Snake) (Grinnell and Camp 1917)

Conservation Issues (Conservation Status)

This species is not known to be threatened, but gartersnakes have been negatively impacted by competition with introduced bullfrogs and non-native fish in some areas.

Taxonomy
Family	Colubridae	Colubrids	Oppel, 1811
Genus	Thamnophis	North American Gartersnakes	Fitzinger, 1843
Species	elegans	Western Terrestrial Gartersnake	(Baird and Girard, 1853)
Subspecies	terrestris	Coast Gartersnake	Fox, 1951
Original Description
Thamnophis elegans - (Baird and Girard, 1853) - Cat. N. Amer. Rept., Pt. 1, p. 34 Thamnophis elegans terrestris - Fox, 1951 - Univ. California Publ. Zool., Vol. 50, p. 499, 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 elegans - Latin - fine or elegant -- "delicately carinated" terrestris - Latin - of the earth - probably refers to the hatitat and the terrestrial nature from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
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. 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 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. Flaxington, William C. Amphibians and Reptiles of California: Field Observations, Distribution, and Natural History. Fieldnotes Press, Anaheim, California, 2021. Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018. 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 conservation status listings for this animal are taken from the July 2022 State of California "Special Animals List" and the July 2022 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and can be downloaded here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check this link to see if there are more current lists. A detailed explanation of the meaning of the status listing symbols can be found on the Special Animals List. For quick reference, I have copied some of them on my Special Status Information page. If no status is listed here, the animal is not included on either 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. This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
Organization	Status Listing	Notes
NatureServe Global Ranking
NatureServe State Ranking
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

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