California Reptiles
& Amphibians

Key to California Gartersnakes

These pages may also be useful when identifying California gartersnakes: Range maps of all CA gartersnakes ID page including pictures of all CA gartersnake species.	In most parts of California, several species of gartersnake inhabit the same area - including as many as four species in some areas. These snakes can often be identified on sight, but sometimes measuring or counting certain scales is necessary to identify a species, especially with snakes in areas where there are species that are similar in appearance, or with snakes that do not have the appearance typical of their species or subspecies. Observing and comparing the scales and features listed in the chart below should help to identify the species of most gartersnakes encountered in California. For more detailed information about scale counts, see the books listed below under references. Scale counts can vary within a particular species, so counting scales will not always work. (For example, T. ordinoides usually has 7 upper labials and 17 mid-body scale rows, but sometimes it has 8 upper labials and 19 mid-body scales, while the same counts are possible with T. elegans which typically has 8 upper labials and 21 mid-body scales.) Comparing all scales is not always helpful either. For example, comparing anal scales is not necessary as all species should have a single anal scale, and comparing the placement of the lateral stripe is not necessary since all California species typically have the lateral stripes on the 2nd and 3rd scale rows (except for Marcy's Checkered Gartersnake, which can be easily identified without looking at the lateral stripes.)
Click on a name link for more information about a snake.	Click on a blue link to see an illustration of the scale count.
Snake	Upper Labials	Lower Labials	Chin Shields	Internasals	Scale Count at Mid-body	Some features differing from sympatric gartersnakes	Snake
Thamnophis atratus atratus Santa Cruz Gartersnake	8 6 and 7 not enlarged	11	Rear pair longer than front	Longer than wide and pointed in front	19 or 21	8 upper labials. Chin shields. Internasals. Yellow on throat. May be missing lateral stripes. No red on sides or head.
Thamnophis atratus hydrophilus Oregon Gartersnake	8 6 and 7 not enlarged	usually 10	Rear pair longer than front	Longer than wide and pointed in front	19 or 21	8 upper labials. Chin shields. Internasals. Vertebral stripe often absent, or present only on neck. Underside of tail often orange or pinkish. No red on sides or head.
Thamnophis atratus zaxanthus Diablo Range Gartersnake	8 6 and 7 not enlarged	11	Rear pair longer than front	Longer than wide and pointed in front	19 or 21	8 upper labials. Chin shields. Internasals. No red on sides or head.
Thamnophis couchii Sierra Gartersnake	8 6th is wider than 7th			Longer than wide, pointed in front	19 or 21	Unstriped morph with no stripes.Upper labials.
Thamnophis elegans elegans Mountain Gartersnake	8 Occasionally 7 6 and 7 are enlarged, higher than wide	10	Front and rear pairs equal in length	Wider than long, not pointed in front	21 Rarely 19	No red on sides. Dorsal and lateral stripes. Upper labials. Chin shields. Internasals.
Thamnophis elegans terrestris Coast Gartersnake	8 Occasionally 7 6 and 7 are enlarged, higher than wide	10	Front and rear pairs equal in length	Wider than long, not pointed in front	21 Rarely 19	Red spotting on sides. Upper labials. Chin shields. Internasals.
Thamnophis elegans vagrans Wandering Gartersnake	8 Occasionally 7 6 and 7 are enlarged, higher than wide	10	Front and rear pairs equal in length	Wider than long, not pointed in front	21 Rarely 19	Upper labials. Chin shields. Internasals. Greyish ground color with black checking and yellow lateral and vertebral stripes.
Thamnophis gigas Giant Gartersnake	8 6th is shorter than 7th	10 - 11		The internasals are slightly shorter than the prefrontals	23 or 21	Large body size. 6th Upper labials.
Thamnophis hammondii Two-striped Gartersnake	8				21	Lack of vertebral stripe. No red on sides.
Thamnophis marcianus Marcy's Checkered Gartersnake	8				21 or 19	Black area of head color extends downward covering the 7th & 8th upper labials. Only gartersnake in its range in California.
Thamnophis ordinoides Northwestern Gartersnake	7 Sometimes 8, rarely 6	8 - 9 Rarely 7 or 10		The internasals are shorter than the prefrontals	17 Rarely 15 or 19	Occasional lack of lateral stripe. Upper labials. Internasals. Highly variable in color and pattern and scalation. Small head.
Thamnophis sirtalis fitchi Common Gartersnake	7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front		19	Dark with red spotting on sides. Yellowish vertebral and lateral stripes. Little or no red on head. Large eyes. Upper labials. Chin shields.
Thamnophis sirtalis infernalis California Red-sided Gartersnake	7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front		19	Red on sides and head. Upper labials. Chin shields.
Thamnophis sirtalis tetrataenia San Francisco Gartersnake	7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front		19	Usually a continuous red lateral stripe bordered with black.Lateral stripes and belly greenish blue. Upper labials. Chin shields.
Snake	Upper Labials	Lower Labials	Chin Shields	Internasals	Scale Count at Mid-body	Some features differing from sympatric gartersnakes	Snake

References

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

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

St. John, Alan D. Reptiles of the Northwest: Alaska to California; Rockies to the Coast. Lone Pine Publishing, 2002.

Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.

Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Brown et. al. Reptiles of Washington and Oregon. Seattle Audubon Society, 1995.