If you're like many people, you might be wary of snakes, but having them around can be a good thing. They help maintain balance in the ecosystem by feeding on slugs, insects, mice, and small amphibians. Here’s a look at the garter snakes that might inhabit your yard. Garter snakes are not the big bad giants of the snake world.
Instead, they’re small to medium-sized and harmless to humans and pets. Garter snakes are secretive and try to stay out of sight.
Garter Snake facts: live in ALL the places | Animal Fact Files
Garter snakes are reptiles. A reptile is an animal that is ectothermic (cold-blooded), scaly, and breathes using lungs; most lay eggs. Being cold-blooded means these animals often bask in the sun to warm their bodies. Garter snakes’ scales are made of keratin, which is what our fingernails are made of! Their scales cover the whole body, even the eyelids. As snakes grow, they shed their old skin. This is called molting.
Garter Snake Classification and Distribution
Garter snakes are in the scientific family Colubridae and the genus Thamnophis. They range from Canada’s subarctic regions to Central America’s southernmost parts. There are about thirty-five species and subspecies, with twelve of them in the United States.
Here are some of those you might see in your yard, based on where you live. All are subspecies of the Common Garter Snake, Thamnophis sirtalis, and differ primarily in color pattern variation.
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Habitat and Behavior
Garter snakes can be found in meadows, gardens, forests, and they prefer areas near water. They like to make dens under big rocks or other support structures like steps, stone walls, and building foundations. Garter snakes hibernate in communities, sometimes with hundreds of snakes! They will hibernate from October to April and sometimes travel long distances to reach a communal den.
These snakes move by wiggling their bodies side to side in an S-shape. They are very fast and use quick movement to ambush prey. They can swim and climb trees too!
Diet and Hunting
They are carnivores! These snakes are small and swallow their prey whole so they will eat anything they can overpower. This includes snails, earthworms, leeches, small fish, grasshoppers, and other insects. Occasionally they will eat small birds and rodents.
These snakes use their excellent sense of smell and vision to hunt prey. Snakes use their tongues as a way to “smell the air.” They do have nostrils primarily for breathing, but by flicking their tongue they can pick up the scent chemicals of prey or predators close by. The tongue goes back into the mouth and fits neatly into the Jacobson’s organ located on the roof of the mouth. Here the information about the chemicals gathered is sent to the brain and decoded!
Reproduction
Garter snakes are one of the few types of snakes that have live births. Females usually give birth to 15-40 young. They are left on their own to hunt after being born.
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Garter Snake Species and Subspecies
Washington’s three garter snake species (common, northwestern and terrestrial) are similar in general appearance and have coloration and patterns that vary regionally and by individual. All traits, especially scale counts, color and pattern, must be examined to correctly identify a garter snake to species. Although little appreciated, these are beautiful snakes with many stunning color variations.
Common Garter Snake (Thamnophis sirtalis)
The common garter snake is a medium-sized dark snake with stripes. It has a dorsal pattern that is the most variable of any of the garter snake species (Thamnophis species). Typically, three stripes are present; a thin dorsal (topside) stripe on the middle of the back and two thin lateral (side) stripes on the second and third dorsal scale rows. The lateral or dorsal stripes may be absent in some individuals. Adults can reach 54 inches total length but individuals in Washington are shorter. The pupil is round. The scales are keeled.
Differences in scale counts are important for distinguishing the three garter snakes in Washington. Common garter snakes usually have 19 scales at mid-body, 7 upper labial scales and 10 lower labial scales. Occasionally, extra labial scales are present.
Eastern Washington
In eastern Washington, common garter snakes are black bodied with bright yellow dorsal and lateral stripes. Distinct red blotches are present on the sides of the body just above the lateral stripes. A red cheek blotch is usually present. The ventral coloration is yellow or buff. Individuals, in some areas, may have blue or turquoise lateral stripes instead of yellow and these snakes usually have blue ventral scales.
Desert striped whipsnakes may be confused with garter snakes. They differ in having smooth scales, 15 dorsal scale rows, and a mid-dorsal area that is dark brown or black with multiple white or yellow stripes on the sides of the body.
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Western Washington
In western Washington, red blotches may or may not be present on the common gartersnake and the stripe coloration is much more variable. Ground color is slate gray or black, sometimes with a bluish tinge. Stripe colors are yellow, green, turquoise or blue. All stripes may be the same color, or the lateral stripes may differ from the dorsal stripe in color. The ventral (underside) coloration is usually yellow or cream under the chin with increasing black pigmentation toward the tail. Snakes with blue lateral stripes usually have blue ventral coloration.
Snakes without red blotches have white patches of skin between the scales on the sides of the body. This trait will not be obvious in most snakes without gently stretching the skin to separate the scales above the lateral stripes. This trait is usually more prominent near the head. Other variations include orange blotches instead of red; blotches only on the anterior portions of the snake; or red blotches that are hidden under dark scales. In very melanistic (dark pigmented) individuals, all the skin between the scales is black and no white or red blotches are present.
In western Washington, northwestern garter snakes and common garter snakes are the most difficult species to distinguish based on coloration.
Habitat and Activity
In Washington, common garte snakes are almost always found near water. Typical aquatic habitats include wetlands, bogs, ponds, lakes, springs, creeks, and rivers. They are good swimmers and can hunt both on and below the water surface. Juvenile common garter snakes have been observed hunting newly metamorphosing pacific treefrogs in shallow, seasonal, water bodies.
Typical terrestrial habitats include sunny areas near water such as meadows, oak patches, forest openings, and shrubby areas. In the spring and fall snakes may be found away from water as they move to and from terrestrial overwintering sites.
Defense Mechanism
Garter snakes defend themselves by releasing the contents of their cloaca and musk glands then smearing this pungent foul-smelling mixture over themselves and their attacker. Some will also regurgitate the contents of their stomach and most will bite.
Dietary Habits and Toxins
Common garter snakes are one of the few vertebrates that can successfully prey on the extremely toxic rough-skinned newt. Research indicates that these snakes harbor significant amounts of active toxin in their tissues after consuming a newt. The amount of toxin in the liver varies depending on the number of newts eaten, but the amount in many cases is enough to severely incapacitate or kill avian predators and negatively affect mammalian predators.
Seasonal Activity and Breeding
At low elevations, activity starts in March and continues into early November. Snakes may remain in the vicinity of the overwintering site for two or more weeks until mating is complete and weather conditions are appropriate for dispersal. At low elevations in western Washington, snakes may be surface active in the vicinity of the overwintering site whenever site conditions warm over about 55° Fahrenheit.
The species breeds in spring after emergence. Males emerge before females and spend time on the surface near the overwintering sites. When a female emerges, the males will attempt to mate with her forming “mating balls” of many males around one female.
After mating, snakes disperse to summer foraging areas. In the lower Puget Sound area, female garter snakes of all three species are commonly found clustered in open grassy areas. This behavior may be related to thermoregulation and gestation.
The young are born in late summer and early fall depending on location. The common gartersnake has the greatest geographical distribution of any gartersnake, occurring in all Washington Ecoregions. Occurrences are patchy in the central Columbia Basin.
Subspecies in Washington
Storm and Leonard 1995 provide detailed descriptions for each subspecies found in Washington: T.s. concinnus occurs in the Pacific Coast and southern Puget Trough ecoregions; T. s. fitchi occurs in eastern Washington ecoregions; and T.s.
Gartersnakes are active during the day and are highly variable in appearance. Their most common pattern is three yellow, olive, or yellowish-green stripes separated by two black or brown stripes. The two lower yellowish stripes are more broad than the center stripe and extend down to to the belly or are separated from it by an often indistinct, sometimes dotted, dark line. Bellies are yellow or pale green. Some coastal and island populations lack stripes altogether and instead display thin, dark bars across the back, or are plain sandy-brown overall with a diffuse pattern of black spots.
Gartersnakes live in virtually every terrestrial and wetland habitat in the state. Gartersnakes mate in spring and fall. Smaller males often pursue larger females. Litters of 1-5 dozen young, 5-9 inches long, are born in July and August. Diets vary widely and can include worms, insects, frogs, toads, fish, salamanders, nestling birds, and small mammals.
Specific Garter Snake Subspecies
Red-sided Garter Snake (Thamnophis sirtalis parietalis)
The Red-sided Garter Snake boasts a striking appearance with its vibrant orange-red stripes running down its black or brown body. These snakes are relatively small, ranging from 18 to 42 inches (46 cm-1.1m) long, with a slender build. One distinctive feature is the red or orange stripes on their sides, giving them their name. These snakes engage in a fascinating mating ritual known as the “mating ball,” where multiple males compete for the attention of a single female. After mating, the females give birth to live young instead of laying eggs.
California Garter Snake (Thamnophis sirtalis infernalis)
The California Garter Snake is associated with wet or marshy areas, so if you live near water, this may be the one you’ll see. It has a basic pattern of yellow or blue stripes over a primarily red body. A row of black spots or blotches appear in a stripe-like pattern. Their average total length is about 22 inches (55 cm), but they can get up to a maximum total length of about 39 inches (2.5 m). They mate in the late winter to early spring, and the female gives birth to live young in mid-summer to early fall.
Valley Garter Snake (Thamnophis sirtalis fitchi)
The Valley Garter Snake has a wide, yellowish stripe on top and a yellowish stripe along the bottom of each side. Red spots run above the side stripes. They grow 18 to 55 inches (0.5-1.4 m) long but average under 36 inches (0.9 m). They range from northern California to southern Alaska and western Canada in habitats that include forests, mixed woodlands, grasslands, scrub, and farmlands, often near ponds, marshes, or streams.
Puget Sound Garter Snake (Thamnophis sirtalis pickeringii)
The Puget Sound Garter Snake is black with a turquoise or black belly and bright yellow or turquoise stripes on the top and sides. It may also have very faint red bars on the sides. Found on Vancouver Island, its adjacent surrounds, and in northwestern Washington in wetlands, marshes, grassy and rocky areas, forests, streams, ponds, lakes, and urban landscapes. Skilled swimmers, they’re well-adapted to semi-aquatic environments. They feed on amphibians, fish, insects, small mammals, and sometimes earthworms and other invertebrates.
San Francisco Garter Snake (Thamnophis sirtalis tetrataenia)
The San Francisco Garter Snake is visually striking, boasting a vivid combination of red, black, and turquoise stripes along its body. Adult females can reach a length of 47 inches (1.2 m), although the average is 39 inches (0.9 m). They occur in two counties in the densely populated San Francisco Peninsula, with some overlap into adjacent areas.
Eastern Garter Snake (Thamnophis sirtalis sirtalis)
Eastern Garter Snakes live in a variety of habitats, including city parks and urban and suburban yards and gardens. Adults are between 18 and 26 inches (46-66 cm) long. You might spot one basking in the sun on piles of logs, stones, and other debris that allow them to quickly hide from predators. to Texas and beyond.
Description: The eastern garter snake (Thamnophis sirtalis) is usually 18 - 26 in (45.7 - 66 cm) long, but occasionally reaches lengths up to 49 in (124 cm). Most individuals can be distinguished from other species by the presence of three yellow longitudinal stripes down a dark body. Some, however, exhibit a checkered body pattern with light stripes and a grayish or reddish body color. Specimens from southern Georgia and Florida are often bluish in background coloration. The belly of garter snakes is white or light yellow.
Garter snakes are similar in appearance to ribbon snakes (Thamnophis sauritus) but ribbon snakes are generally more slender and garter snakes have vertical black lines on their lip scales. Additionally, in garter snakes the lateral yellow lines are on scales 2 and 3 whereas they are on scale rows 3 and 4 in ribbon snakes. On garter snakes they are on scales 2 and 3.
Range and Habitat: Garter snakes are common throughout the Southeast and most of North America and are found in a wide variety of habitats, including meadows, marshes, woodlands, and hillsides. They tend to prefer moist, grassy environments and are often found near water, such as the edges of ponds, lakes, ditches, and streams.
Habits: Garter snakes may be active by day or night and are often found under boards or other debris. They are viviparous (give birth to live young) and sometimes have more than 50 babies. Common garter snakes feed on worms, slugs, frogs, toads, salamanders, fish and tadpoles.
Conservation Status: Garter snakes are common in our region and are not protected throughout most of it.
New Mexico Garter Snake (Thamnophis sirtalis dorsalis)
New Mexico Garter Snakes can vary in appearance, but they typically display a series of yellow or greenish-yellow stripes running along their body, often bordered by black or dark brown stripes. Adults are 18 to 42 inches (46-107 cm) long. They inhabit various aquatic and riparian habitats, including streams, rivers, ponds, and marshes, where they can be found foraging for prey such as fish, amphibians, insects, and small mammals.
Texas Garter Snake (Thamnophis sirtalis annectens)
The Texas Garter Snake is found predominantly in central Texas, with populations in southwestern Kansas and western Oklahoma. They have a greenish-black back with a bright orange or red stripe down the center and yellowish stripes on the sides. Adults are from 15 to 28 inches (38-71 cm) in length. If handled, they will flail around and may release a foul-smelling odor. They’re usually seen close to water.
Maritime Garter Snake (Thamnophis sirtalis pallidulus)
Maritime Garter Snakes are highly variable in color and pattern but tend to be brown, dark green, or black with three longitudinal yellow stripes. Many have white, brown, or black checkered or speckled patterning. They’re typically 18 to 36 inches (46-91 cm) long. and southeastern Canada are the most common snakes in their areas, including forests, wetlands, shrublands, shorelines, fields, rocky areas, and urban landscapes.
Blue-striped Garter Snake (Thamnophis sirtalis similis)
The Blue-striped Garter Snake is black or very dark brown with three stripes-a yellowish one on top and a pale to bright blue one on each side. Their adult length is about 20 to 23 inches (50-60 cm).
Garter Snakes in Acadia National Park
The garter snake is one of 5 types of snakes in Acadia National Park. Others are the ringneck snake, milk snake, smooth green snake, and redbelly snake. None of them are venomous.
Summary of Garter Snake Characteristics
Here is a summary of the key characteristics of Garter Snakes:
| Characteristic | Description |
|---|---|
| Size | Small to medium-sized, 15-55 inches |
| Appearance | Slender bodies, longitudinal stripes, varied coloration (green, brown, black, red) |
| Habitat | Meadows, gardens, forests, near water |
| Diet | Carnivorous: snails, earthworms, insects, small fish, rodents |
| Reproduction | Live birth, 15-40 young |
| Defense | Releasing foul-smelling musk, regurgitation, biting |
The African Garter Snake (Elapsoidea)
The African garter snake is any of several small, poisonous, semiburrowing snakes in the genus Elapsoidea, which inhabit central and southern Africa. Adult length averages less than 3 feet (90 centimeters). The head is short with small round eyes and an enlarged scale on the snout. The body is moderately slender, the tail is very short and pointed, and the scales are glossy. Coloration and pattern vary among the species and subspecies. Several are black with narrow white rings. Others are uniformly yellowish or brownish with faint ring patterns. One snake, E. guentheri, has delicate white rings.
African garter snakes often inhabit termite mounds but may be found during the day in a variety of other retreats, such as logs and holes. They are active at night, feeding mainly on small snakes and lizards and their eggs. The African garter snakes belong to the cobra family Elapidae, characterized by hollow, fixed front fangs and a potent, paralyzing venom. Although potentially dangerous, they have a calm temperament and bite only if seized or injured. They lay eggs, but little else is known of their breeding habits.
