The Two-striped Gartersnake typically has a single light stripe low on each side of the body but lacks the light stripe on top of the back which is present in most other gartersnakes found in California.
Sign, San Diego County park
Central Coast Dark Morph Two-striped Gartersnakes, and Others with Aberrant Pigmentation or Unusual Patterns
These snake are unusual hybrids of the Two-striped Gartersnake and the Diablo Range Gartersnake, Thamnopis atratus zaxanthus. Note the thin yellow vertebral stripe that is not present on T. hammondii and is much thinner than that found on T. atratus. T. atratus is so scarce at the edge of its range in San Luis Obispo and Santa Barbara counties that they breed with T. hammondii which is more abundant in the area.
A Two-striped Gartersnake
filmed in San Diego County.
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.
24 - 40 inches long (61 - 102 cm). Most often 18 - 30 inches long (46 - 76 cm).
Neonates are 7.5 - 9 inches (19 - 23 cm).
A medium-sized snake with a head barely wider than the neck and keeled dorsal scales.
Color and Pattern
Appearance is variable - there are two basic pattern morphs - striped, and spotted.
Both have a drab olive, brown, or dark gray ground color, with no dorsal stripe, except for a partial stripe on the neck.
The striped morph has a yellowish to gray lateral stripe on each side, and a fairly uniform dorsal coloring, with only faint spotting.
The spotted morph has two rows of small dark spots on each side and lateral stripes are often not present.
Light areas between the scales between the rows of dark spots can create a checkered appearance.
The underside is pale yellow or orange, unmarked, or with dark smudging.
"Black individuals, sometimes with obscure or without laterals sripes, or even spots..." are found along the outer coast in San Luis Obispo County, and can be expected from Monterey Bay to Santa Barbara County. (Stebbins, 2003)
A dark green and a reddish color morph occur along the Piru River in Ventura County. (Stebbins, 2003)
A melanistic population occurs on Catalina Island.
Also active at night and at dusk during hot weather in some areas.
Can be active most of the year depending on weather conditions. Has been found from January to November.
Like most gartersnakes, when picked up, will often strike repeatedly and release cloacal contents and musk.
When threatened, some Two-striped Gartersnakes assume a defensive pose with the head flattened into a triangular shape that makes it look like the head of a venomous snake, such as a rattlesnake, to scare away the threat.
Diet and Feeding
Eats fish, fish eggs, tadpoles, newt larvae, small frogs and toads, leeches, and earthworms.
Garden Slender Salamanders - Batrachoseps major (and their detached tails) and aquatic leeches hava also been found in the stomach contents of T. hammondii. (Edward L. Irvin, et al. Herpetological Review 34)1), 2003.
Forages for food in and under water.
An adult T. hammondii was observed in an underwater ambush position about 15 cm below the surface, compressing its body into side-by-side loops while using its tail to anchor itself in stable aquatic vegetation. From this position it periodically quickly lunged forward at its prey. (Edward L. Ervin and Robert N. Fisher, Herpetological Review 38(3), 2007.
Mating has been observed in late March and early April. An average litter of about 15 live young are born from July to October.
Females are known to store sperm for later use.
Among the most aquatic of the gartersnakes. Generally found near water sources - pools, creeks, cattle tanks, and others, often in rocky areas. Associated vegetation: oak woodland, willow, coastal sage scrub, scrub oak, sparse pine, chaparral, and brushland.
Ranges continuously from near Salinas in Monterey County south along the coast mostly west of the south Coast Ranges, to southern California where it ranges east through the Transverse Ranges, and south through the coastal area and the Peninsular Ranges into northern Baja California. Occurs in some perennial desert slope streams north of the Transverse Ranges and east of the Peninsular Ranges, and into the Mohave Desert in Victorville. Also occurs on Catalina Island.
Occurs along the western part of northern Baja California, and in parts of Baja California Sur.
At elevations from sea Level to 6,988 ft. (2130 m).
Notes on Taxonomy
Formerly classified as a subspecies of Thamnophis couchii. T. digueti was synonymized with T. hammondii by McGuire and Grismer (1993, Herpetologica 49:354-365).
The Santa Catalina population of T. hammondii has been treated as a distinct subspecies by the California Dept. of Fish and Game - Santa Catalina garter snake, Thamnophis hammondii ssp.
Designated a California Species of Special Concern and protected by the state.
Loss of wetland habitats have contributed to a reduction in the range of this snake.
Declines in population of the species have been attributed to human impacts, including urban development and flood control in the southern part of its range, and habitat modification by livestock, drought, loss of native prey and predation by alien species in its northern range.
(Jennings and Hayes 1994)
"...restoration of aquatic habitat and supplementation with artificial wetlands should be explored as a management option in extirpated sites." Terrestrial habitat surrounding the aquatic habitats, especially rodent burrows, are utilized for overwintering and should also be protected.
(Thomson, Wright, and Shaffer, 2016)
North American Gartersnakes
(Kennicott, 1860 )
Thamnophis hammondii - (Kennicott, 1860) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 12, p. 332
Rossman, Douglas A., Neil B, Ford, & Richard A. Siegel. The Garter Snakes - Evolution and Ecology. University of Oklahoma press, 1996.
Robert C. Thomson, Amber N. Wright, and H. Bradley Shaffer. California Amphibian and Reptile Species of Special Concern. University of California Press, 2016.
Mark R. Jennings and Marc P. Hayes. Amphibian and Reptile Species of Special Concern in California. Report to California Department of Fish and Game. 1994.
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.
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.
The following conservation status listings for this animal are taken from the November 2020 California "Special Animals List" and the November 2020 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and available here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check the link to see if there are more recent lists.
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.
The 2019 Special Animals List lists the population on Santa Catalina Island as a separate subspecies, Thamnophis hammondii pop. 1. - Santa Catalina gartersnake. This listing for this snake is shown below the listings for the other populations of T. hammondii.
This is the listing for Thamnophis hammondii - two-striped gartersnake:
NatureServe Global Ranking
Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.
NatureServe State Ranking
Vulnerable—Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation from the state.
Apparently Secure—Uncommon but not rare in the state; some cause for long-term concern due to declines or other factors.
U.S. Endangered Species Act (ESA)
California Endangered Species Act (CESA)
California Department of Fish and Wildlife
Species of Special Concern
Bureau of Land Management
USDA Forest Service
This is the listing for Thamnophis hammondii pop.1 - Santa Catalina gartersnake:
NatureServe Global Ranking
The species is: Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.
This subspecies is: Critically Imperiled—At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors. Imperiled—At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.
NatureServe State Ranking
Critically imperiled in the state because of extreme rarity (often 5 or fewer populations) orbecause of factor(s) such as very steep declines making it especially vulnerable to extirpation from the state.