A Guide to the Amphibians
and Reptiles of California

Key to California Gartersnakes

These pages may also be useful when identifying California gartersnakes: Range maps of all CA gartersnakes Identification page including pictures of all CA gartersnake species. Upper Labial Scales Comparison Pictures	8 species and 14 kinds of gartersnakes are native to California. In most parts of the state several species of gartersnake inhabit the same area - up to four species in some areas. These gartersnakes can often be identified on sight by color and pattern, but sometimes counting or measuring specific scales is needed to identify a species where different species are similar in color and pattern. Observing and comparing the scales and other features listed in the chart below might help to identify the species. Click on the links to see photos that illustrate these scale counts, but keep in mind that the snakea in the photos may vary somewhat from snakes you might encounter. Scale counts can vary within a particular species, so, unfortunately, 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 gartersnakes 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 by color and pattern with no need to examine the lateral stripes.) Some of these scale observations can also be confusing. For example, the enlargement of upper labial scales 6 and 7, even when you look at the pictures I have provided, is not alwasy easy to determine. For even more detailed information about scale counts, see the books listed below as references from which I have made these descriptions.
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	Number of Upper Labial Scales	Number of Lower Labial Scales	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 (7th longer than 6th)	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 (7th longer than 6th)	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 (7th longer than 6th)	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		Rear longer than front in this example	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	Usually there is red spotting on sides (but not always.) 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	Rear longer than front	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 Valley Gartersnake	Usually 7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front	Internasals	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 (and South Coast Gartersnake)	Usually 7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front	Internasals	19	Red on sides and head. Upper labials. Chin shields.
Thamnophis sirtalis tetrataenia San Francisco Gartersnake	Usually 7 Occasionally 8, rarely 6 or 9 Often with black wedges	10	Rear longer than front	Internasals	19	Usually a continuous red lateral stripe bordered with black.Lateral stripes and belly greenish blue. Upper labials. Chin shields.
Snake	Number of Upper Labial Scales	Number of Lower Labial Scales	Chin Shields	Internasals	Scale Count at Mid-body	Some features differing from sympatric gartersnakes	Snake

Compare all head scales of - *T. atratus, T. elegans, T. sirtalis,* and T. couchii
Compare the tops of the heads of - *T. sirtalis* and T. ordinoides

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.

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