How to Identify the Western Terrestrial Garter Snake (Identification Guide)
A guide to recognizing the Western Terrestrial Garter Snake by its variable striping, keeled scales, and wide western range.
Read the full Western Terrestrial Garter Snake encyclopedia entry →
Key identifying features
The Western Terrestrial Garter Snake (Thamnophis elegans) is one of the most widespread and variable garter snakes in western North America. Identification relies on a combination of a bold dorsal stripe, strongly keeled scales, and a stout, medium-sized body rather than any single fixed color pattern, since this species shows enormous regional variation.
Coloration & pattern
Most individuals show three light stripes running the length of the body: one down the center of the back and one along each side, set against a background that ranges from brown, gray, or olive to nearly black. The side stripes typically sit on the second and third scale rows counting up from the belly. Between the stripes, many populations display a checkerboard of dark spots or blotches, which can be faint or quite prominent depending on the subspecies and locality. Some coastal and mountain populations are almost uniformly dark with barely visible stripes, while others show a vivid yellow or orange vertebral stripe. The belly is usually pale gray, olive, or bluish, sometimes with dark flecking along the edges.
Head, eyes & scales
The head is only slightly wider than the neck and lacks the exaggerated bulge seen in some water-associated species. Eyes are of moderate size with round pupils, typical of nonvenomous colubrid snakes. The dorsal scales are strongly keeled (ridged down the center), giving the body a rough, matte texture rather than a glossy sheen. Scale rows are typically in 19-21 rows at midbody, and the anal plate is single.
Size & body shape
Adults commonly reach 18 to 42 inches (46-107 cm) in total length, with most individuals falling in the 24-36 inch range. The body is moderately stout with a tail that tapers gradually, making up roughly a quarter of the total length. Overall build is more robust than slender ribbon-type garter snakes.
Range & habitat where you'll see it
This species occupies an enormous range across the western United States and adjacent Canada and Mexico, from the Pacific coast to the Rocky Mountain front, and from sea level up to high mountain meadows above 10,000 feet. It is found near streams, ponds, wet meadows, and grasslands, but unlike some garter snakes it also ranges well away from permanent water into drier upland habitat, especially in mountainous terrain.
How to tell it apart from look-alikes
Within its range it can be confused with other garter snakes such as the Common Garter Snake, which usually has smoother-looking stripes and less checkering, and the Northwestern Garter Snake, which is smaller and more slender with less pronounced keeling variation. The strongly keeled scales, checkered pattern between the stripes, and tolerance of both aquatic and dry upland habitats help distinguish the Western Terrestrial Garter Snake. Regional color forms (striped, checkered, or nearly patternless) mean local field guides are the best supplement to general identification.
Frequently asked questions
What is the easiest way to identify a Western Terrestrial Garter Snake?
Look for a stout-bodied snake with strongly keeled scales, three light stripes on a brown or olive background, and often a checkerboard pattern of dark spots between the stripes.
Does this snake always have three stripes?
No. Some populations, especially in coastal or mountain areas, can appear nearly uniform dark or have faint stripes, so pattern alone should not be the only clue.
How can I tell it from a Common Garter Snake?
The Western Terrestrial Garter Snake tends to have rougher, more strongly keeled scales and more checkering between the stripes, while Common Garter Snakes usually look smoother-patterned.
Is this snake found near water?
It is often found near streams and ponds but is also known to range into dry grassland and upland habitat far from permanent water, unlike more strictly aquatic garter snakes.
Is the Western Terrestrial Garter Snake venomous?
It is not considered dangerously venomous to humans and is classified as a harmless colubrid snake.