Almost everyone can identify a “garter snake” in California!
But here’s the problem:
There are multiple species and sub-species of garter snakes! Therefore, figuring out the identity of the SPECIFIC snake you are observing can be challenging. This is especially true since many of them have similar appearances and behaviors.
Today, you are going to learn about 10 garter snake species in California!
- *Just a quick note – to be officially considered a garter snake, the species must be in the genus Thamnophis*
#1. Terrestrial Garter Snake
- Thamnophis elegans
- Adults range from 18 to 41 inches in length.
- Most adults have three yellow, light orange, or white stripes; one down their back and two down their sides.
- Coloration is widely variable. Individuals may be brownish or greenish. Some have red and black spots between the stripes, and occasionally all black individuals are found.
This garter snake can be difficult to identify in California!
Even trained herpetologists have issues! Its coloration varies widely, and there are believed to be 6 subspecies, although scientists still debate this.
Terrestrial Garter Snakes occupy various habitats, including both grasslands and forests. They can even be found in mountainous areas up to 13,000 feet above sea level. As the name suggests, they’re primarily found on land. But interestingly, these garter snakes can swim well!
This species is the only garter snake in California with a tendency to constrict prey! Most garter snakes grab their prey quickly and just swallow, rubbing their prey against the ground if necessary.
Terrestrial Garter Snakes aren’t aggressive or dangerous, but they do possess mildly venomous saliva! It can cause a muscle infection or even kill some muscle tissue. Most bites on humans just cause pain and some swelling.
#2. Valley Garter Snake
- Thamnophis sirtalis fitchi
- Adults range from 18 to 55 inches in length.
- Coloration is brown to black with three yellow stripes; one down the back and one down each side.
- Pronounced red bars between the yellow stripes. Yellowish chin, jaw, and belly, and a black head, which often has red sides.
- Subspecies of the Common Garter Snake.
Valley Garter Snakes are found in various habitats, including forests, wetlands, scrublands, fields, shorelines, and rocky areas. They’re also well adapted to humans and are often found in urban areas.
Look for these garter snakes in California under rocks, logs, and other objects, which they use for cover and thermoregulation. During the winter, they hibernate, often communally below the frost line. They will use a variety of underground cavities, including mammal and crayfish burrows, rock crevices, ant mounds, as well as manmade spaces such as foundations and cisterns.
When disturbed, Valley Garter Snakes will try to escape into the water and are excellent swimmers. If captured, be prepared for them to release musk and feces onto your hands! They may also strike, but only if they feel extremely threatened.
The Valley Garter Snake is considered a species of low risk. They are quite common and adapt well to human-modified habitats. However, they are frequently killed on roadways and are sometimes killed out of fear.
#3. San Francisco Garter Snake
- Thamnophis sirtalis tetrataenia
- Adult snakes can reach up to 36 inches (sometimes even more) in length.
- Burnt-orange head with a slender turquoise-blue body featuring bold stripes.
- The stripes run down the snake’s side in a black, orange-red, black pattern.
Considered by some to be the most beautiful garter snake in California!
This striking creature is a subspecies of the Common Garter Snake. They are extremely shy and difficult to locate and are only found in a small area in California. The best places to find San Francisco Garter Snakes are near densely vegetated ponds with nearby open hillsides. Areas with cattails, bullrushes, and spike rushes are used for cover, and open grassland areas are essential for basking.
San Francisco Garter Snakes are in danger of extinction in California.
Unfortunately, they are often illegally collected because of their incredible beauty. They also face habitat loss due to commercial and agricultural development.
In addition, two other factors have contributed to their decline. First, the California Red-legged Frog, one of their main prey species, is also in decline. Second, American Bullfrogs, which prey on the snakes themselves have been introduced to California from the east.
Interestingly, these garter snakes can eat California Newts, which are extremely toxic to most other animals.
#4. California Red-sided Garter Snake
- Thamnophis sirtalis infernalis
- Adults range from 25 to 39 inches in length, with the females being larger.
- Prominent yellowish to bluish stripes. Red and black-barred stripes run in between.
- Slender garter snakes with a red or orange head.
- Subspecies of the Common Garter Snake.
These beautiful garter snakes occupy various habitats near the coasts of California. Look for them near bodies of water such as marshes, streams, ponds, and ditches.
Red-sided Garter Snakes are primarily active during the day. They feed on a wide range of prey, including frogs, newts, fish, birds, eggs, small mammals, reptiles, earthworms, slugs, and leeches. In addition, they can feed on adult Pacific Newts which are poisonous to most predators.
When disturbed, they typically try to escape into the water if available. If captured, you can expect them to bite and defecate on your hand!
The California Red-sided Garter Snake has been listed as endangered since 1967. They face habitat loss due to commercial and agricultural development in California.
#5. Checkered Garter Snake
- Thamnophis marcianus
- Adults are typically 18 to 24 inches in length.
- Coloration is typically greenish. They have three yellow or orange stripes; one down the center of the back and one down each side.
- Look for a distinctive black checkerboard pattern on its back.
- Cream or yellow crescent marks on each side of the head are followed by a dark blotch on the neck.
The Checkered Gartersnake is most commonly found in the southeast corner of California in desert and grassland habitats. Look for them near water sources, such as rivers, lakes, wetlands, cattle tanks, canals, and ditches. Living in arid conditions, these garter snakes are incredibly good at finding water sources.
These garter snakes are active both day and night, depending on the temperature. For example, they are more nocturnal during the heat of summer.
Checkered Gartersnakes are opportunistic predators who feed on a wide variety of prey. They typically consume frogs, salamanders, toads, earthworms, small fish, lizards, snakes, slugs, and crayfish. However, they’ve also been reported to eat mice, raw horse meat, and other snakes of their own species in captivity!
Their populations are not currently threatened. Luckily, they tolerate human development relatively well, although draining wetlands and other water sources harm their population. These garter snakes are also able to co-exist with introduced species like the American Bullfrog.
#6. Sierra Garter Snake
- Thamnophis couchii
- Adults range from 18 to 38 inches in length.
- Coloration is widely variable and may be olive-brown, dark brown, or blackish. Darker blotches on the back and upper sides, which may be obscured in individuals with darker coloration.
- A light stripe on the back and sides may be present but isn’t distinctive except on the neck.
Sierra Garter Snakes are found in California in oak woodlands, coniferous forests, chaparral, pine juniper, and sagebrush. They are almost always found in association with a water source such as creeks, rivers, meadow ponds, or small lakes. They are typically located at elevations between 3000 and 8000 feet above sea level.
These garter snakes primarily feed on fish and amphibians and their larvae, including frogs, tadpoles, trout, and salamanders. This species has been observed eating adult Pacific Newts which are toxic to most predators.
Not much is known about the breeding habits of the Sierra Garter Snake. However, the females have been observed giving birth to live young in late July.
They are not believed to be a threatened species. However, the introduction of non-native fish and American Bullfrogs to their range may hurt their population. Scientists are currently monitoring the situation.
#7. Giant Garter Snake
- Thamnophis gigas
- Adults are LARGE and typically reach at least 64 inches in length.
- Coloration is brownish to olive.
- A yellow stripe down the back and a light stripe down each side.
This species is the LARGEST garter snake found in California!
Look for Giant Garter Snakes in and around wetlands and waterways such as irrigation and drainage canals, ponds, sloughs, small lakes, and low-gradient streams. Unfortunately, much of their original habitat has been lost, and they can now frequently be seen in flooded rice fields.
During the winter, these garter snakes move to higher elevations out of flood zones. They hibernate from early November to April in small mammal burrows and other underground crevices.
Sadly, Giant Garter Snakes are threatened. Experts believe that they may soon be in danger of extinction. They face threats from habitat loss and fragmentation, water pollution, road mortalities, predation from introduced species, and changes in agricultural and land management practices.
#8. Aquatic Garter Snake
- Thamnophis atratus
- Adults range from 18 to 40 inches in length.
- Coloration varies greatly depending on location and subspecies.
- They may be pale grey with alternating rows of dark blotches on the sides, dark brown with less distinct borders, or nearly all black.
- May have a yellow stripe down the back or on the neck.
The Aquatic Garter Snake occupies various habitats in California, including brushlands, woodlands, grasslands, and forests. But, as the name suggests, they are always near a water source such as a pond, marsh, stream, or lake.
These snakes prey on fish, salamanders, toads, and newts. They don’t constrict their prey but may use their body to encircle it in shallow water and then strike to prevent it from escaping.
Aquatic Garter Snakes feel the safest in the water. If they feel threatened or need to escape, they flee as quickly as possible to the nearest source of water!
There are THREE subspecies of the Aquatic Garter Snake, and they are named for the approximate location they can be found; Santa Cruz, Oregon, and the Diablo Range!
#9. Two-striped Garter Snake
- Thamnophis hammondii
- Adults typically range from 18 to 30 inches.
- Coloration is variable – dark gray, drab olive, or brown with a light stripe on the neck.
- Some individuals have yellow to gray stripes down each side, while others have two rows of dark spots down each side and typically lack a light stripe.
This highly aquatic garter snake prefers habitats close to permanent or semi-permanent water sources in California. They can be found up to 7,000 feet of elevation above sea level.
Two-striped Garter Snakes typically hunt in water and prey on fish, fish eggs, tadpoles, newt larvae, small frogs and toads, leeches, and earthworms. They even have the interesting behavior of holding themselves underwater using their tail while lunging for passing prey!
Interestingly, when the Two-Striped Garter Snake is threatened, they will sometimes mimic a venomous snake by flattening their head into a triangular shape. Then, when picked up, they use the same tactics as other garter snakes, releasing musk, defecating, and striking.
This species has seen a decline primarily due to habitat loss. Drought and destruction of wetlands for commercial and agricultural purposes have been the main contributor.
#10. Northwestern Garter Snake
- Thamnophis ordinoides
- Adults average between 12 and 24 inches in length.
- COLORATION IS HIGHLY VARIABLE. Individuals can be blackish, olive, brownish, bluish, or gray, sometimes with a reddish tint.
- Typically has three stripes, one down the back and one down each side. The color of these stripes can be red, yellow, orange, tan, white, greenish, or blue; however, on certain snakes, the stripes may be dull, narrow, or absent!
The Northwestern Garter Snake prefers damp areas in northern California with lots of vegetation and open sunny areas. They may be spotted near houses and are often found when moving boards, logs, or other objects that they use for cover.
This species is predominantly terrestrial. However, these garter snakes can swim, and some local individuals have been observed hunting in the water! They feed mainly on slugs and earthworms, but they also prey on snails, small amphibians, and possibly fish.
The Northwestern Garter Snake will typically flee into dense vegetation if disturbed. One study found that individuals with stripes usually move away quickly because their stripes make it difficult for predators to determine their speed. But plain or spotted individuals frequently freeze while fleeing because their excellent camouflage helps them blend in while they’re motionless.
Do you need additional help identifying garter snakes?
Try this field guide!
Which of these garter snakes have you seen in California?
Leave a comment below!