 Range in California: Green
Click the map for a guide
to the other subspecies.
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Adult 1, Mendocino County |
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Adult 1 in habitat,
Mendocino County |
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Adult 2, Mendocino County |
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Adult 3, Mendocino County |
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| Juvenile, Mendocino County |
Adult without dorsal stripe, Del Norte County © Alan Barron |
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Adult intergrade, Marin County. |
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"
We were just about to leave after lunch when I saw this guy slip into the water out of the corner of my eye. I started changing lenses knowing he would come up nearby as the pool was only 4 feet across. You can imagine my surprise to see him come up with this very angry trout. I took a number of shots as they fought. They were in still water about 4 inches down. They even went over a 2 foot waterfall but the snake never let go. Eventually he got his back end up on a rock, slowly dragged the fish out and eventually began swallowing it."
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Thomas Kavenaugh
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North of the San Francisco Bay, there is a very large intergrade range between T. a. hydrophilus and T. a. atratus or T. a. zaxanthus. The snakes in this area were formerly named T. a. aquaticus (or T. couchii aquaticus.) This subspecies is no longer recognized. Look here for more pictures and information about these intergrades.
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| A series of an Oregon Gartersnake eating a fish in Trinity County. © Kevin Andras. |
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| Juvenile, Mendocino County |
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| Habitat |
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Habitat, Mendocino County |
Habitat, Mendocino County. These small pools of water along the edge of a wide riverbank in summer, contained Foothill Yellow-legged Frogs and tadpoles, Bullfrogs, and Oregon Gartersnakes. |
Habitat, Mendocino County |
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More pictures of this animal and its natural habitat are available on our Northwest Herps page.
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| Short Video |
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An Oregon Gartersnake basks on a rock in a
River in Mendocino County, and swims away. |
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Description |
Nonvenomous |
| 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 |
| 18 - 40 inches long (46 - 102 cm). Most snakes encountered are generally 18 - 28 inches long (46 - 71 cm). Neonates are 7 - 10 inches ( 18 - 25 cm). |
| Appearance |
| A medium-sized slender snake with a head barely wider than the neck and keeled dorsal scales. Ground color is gray, olive-gray, or brownish. This snake may have a light stripe on the back and a light stripe along the lower part of each side. The dorsal stripe and the side stripes may be absent or obscured, not contrasting sharply with the ground color, leaving a checkered appearance instead of striped. There are usually alternating dark spots on the sides. The throat is light. The underside is light and unmarked with a pinkish or purplish tint toward the tail. |
| Behavior |
A highly-aquatic snake, able to remain underwater, but also found away from water. Active during the day, and after dark during very hot weather. Can be active most of the year when conditions allow, but primarily found spring through fall.
When threatened, this snake will often escape into water, hiding on the bottom. If it is frightened when picked up, it will often strike repeatedly and release feces from the cloaca and expel musk from anal glands.
Adults have been found to forage actively, neonates are sit-and-wait foragers, and juveniles practice both forms of foraging. |
| Diet |
| Probably eats mainly amphibians and their larvae, including frogs, tadpoles, and aquatic salamander larvae (newts and giant salamanders, Taricha and Dicamptodon ), but small fish are also eaten. Captives have also taken small rodents. |
| Reproduction |
| Courtship has been observed during March and April. Young are born live late summer to early fall. |
| Range |
| From northern Sonoma County north along the coast to Douglas County, Oregon, ranging east throughout the north coast ranges and to the lower Pit River area. Absent from much of the coast around Humboldt County. |
| Habitat |
| Creeks, streams, rivers, small lakes and ponds, in woodland, brush and forest. Seems to prefer shallow rocky creeks and streams. |
| Taxonomic Notes |
This snake is known to hybridize with T. couchii in Shasta County. For a long time T. atratus was considered a subspecies of T. couchii. In 1987 it was classified as a distinct species.
North of the San Francisco Bay, there is a very large intergrade range between the Oregon Gartersnake and T. a. atratus or T. a. zaxanthus. The snakes in this area were formerly classified as T. a. aquaticus (previously T. couchii aquaticus.) |
| Conservation Issues (Conservation Status) |
| Not known to be threatened, but gartersnakes have been negatively impacted by competition with introduced bullfrogs in some areas. |
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Taxonomy |
| Family |
Colubridae |
Colubrids |
| Genus |
Thamnophis |
North American Gartersnakes |
| Species |
atratus |
Aquatic Gartersnake |
Subspecies
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hydrophilus |
Oregon Gartersnake |
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Original Description |
Thamnophis atratus - (Kennicott, 1860) - in Cooper, Expl. Surv. R.R. Miss. Pacific, Vol. 12, Book 2, Pt. 3, No. 4, p. 296
Thamnophis atratus hydrophilus - Fitch, 1936 - Amer. Midland Nat., Vol. 17, p. 648
from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
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Meaning of the Scientific Name |
Thamnophis - Greek - thamnos - shrub or bush, and ophis - snake, serpent
atratus - Latin - clothed in black, mourning - refers to the dark dorsal color
hydrophilus - Greek - hydor - water, and philus - loving - refers to the snakes aquatic proclivities
from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
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Alternate Names |
Formerly T. couchii hydrophilus
Oregon Aquatic Garter Snake
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| Other California Gartersnakes |
T. a. atratus - Santa Cruz 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
T. s. tetrataenia - San Francisco Gartersnake
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More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
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.
Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.
Rossman, Douglas A., Neil B, Ford, & Richard A. Siegel. The Garter Snakes - Evolution and Ecology. University of Oklahoma press, 1996.
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The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.
This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
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Organization
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Status Listing
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| U.S. Endangered Species Act (ESA) |
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| California Endangered Species Act (CESA) |
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| California Department of Fish and Game |
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| Bureau of Land Management |
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| USDA Forest Service |
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| Natureserve Global Conservation Status Ranks |
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World Conservation Union - IUCN Red List
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Range in California: Green 
