Almost everyone can identify a “garter snake” in Arizona!
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 4 garter snake species in Arizona!
- *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 Arizona!
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 Arizona 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. Black-necked Garter Snake
- Western Black-necked Garter Snakes are dark olive with an orange-yellow stripe down the back and a yellow to white stripe down each side. It can be up to 42 inches long.
- Eastern Black-necked Garter Snakes are smaller and only grow up to 20 inches in length. They have a checkered pattern of black and yellow on their body, in between their three stripes.
- Both subspecies have a gray head that contrasts strongly with the body. In addition, there is a dark blotch on each side of the neck.
This species is found in many habitats, including desert scrub, plains, arid grasslands, and pine-oak woodlands. They’re almost always found in Arizona in association with water sources such as streams, ciénegas, and cattle tanks.
There are two sub-species of this garter snake; the Western AND Eastern. They look different (see photo above), but they also behave uniquely. The Western subspecies (Thamnophis cyrtopsis cyrtopsis) are water snakes and most often found in the actual water. The Eastern (Thamnophis cyrtopsis ocellatus) subspecies prefer to live on DRY LAND that is very close to water.
The Black-necked Garter Snake’s preferred prey is frogs, toads, and their tadpoles, including poisonous species like the Sonoran Desert Toad. However, they have been known to feed on a wide range of other prey, including earthworms, skinks, salamanders, crustaceans, and birds.
Black-necked Garter Snakes adapt well to introduced species like the American Bullfrog. They have also benefited from the creation of cattle tanks since these snakes are dependent upon water.
#3. 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 southeastern Arizona 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.
#4. Mexican Garter Snake
- Thamnophis eques
- Adults may grow up to 44 inches in length. Coloration is black, brown, olive, tan, or rust.
- Three creamy yellow stripes, one down the back and one down each side, may have dark blotches on each side of the neck.
- Noticeably large head compared to other garter snakes, black outlined scales on the lower face.
This secretive garter snake is hard to find in Arizona! Their preferred habitats are near water sources with DENSE vegetation.
The best time to find Mexican Garter Snakes is in the morning, when they’re often active or basking in the sun, or in the early evening. They are highly aquatic and primarily feed on frogs and fish. Try walking close to a water’s edge, where you may see one fleeing into the water!
Sadly, this snake has been listed as threatened under the U.S. Endangered Species Act since 2014. Their decline was believed to have been caused by habitat destruction and the introduction of non-native species.
Do you need additional help identifying garter snakes?
Try this field guide!
Which of these garter snakes have you seen in Arizona?
Leave a comment below!