Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Widely distributed across North America, from the Atlantic to the Pacific coast, and from Subarctic Canada to Southern Florida and parts of Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous; possesses Duvernoy's glands and is technically opisthoglyphous (rear-fanged).
Danger Level
Harmless / Low Risk. Bites may cause minor localized swelling or itching in sensitive individuals, but they have no medical significance for humans.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
IUCN Red List: Least Concern. Populations are stable, though local declines occur due to habitat loss and pesticide use affecting their prey.
Physical Description
Characterized by three longitudinal stripes (one dorsal and two lateral) that are usually yellow, green, or white. The background color is dark olive, brown, or black with a 'checkerboard' pattern between stripes. Scales are heavily keeled, and the head is slightly wider than the neck with large eyes and round pupils.
Size & Dimensions
The specimen appears to be an adult approximately 18-26 inches in length. Species typical range is 18 to 54 inches (46–137 cm).
Habitat
Generalist species found in forests, grasslands, fields, and suburban gardens. They prefer areas near water sources like marshes, streams, or ponds. Found from sea level up to high mountain elevations.
Behavior & Temperament
Diurnal and active. When threatened, they may flatten their bodies to appear larger, strike, or release a foul-smelling musk (cloacal secretions). Generally docile but will bite if handled roughly.
Diet & Feeding
Active forager specializing in amphibians (frogs, toads, salamanders), earthworms, small fish, slugs, and occasionally small rodents or birds. They swallow prey alive without constriction.
Reproduction
Viviparous (gives birth to live young). Breeding occurs in spring shortly after emerging from brumation. Litters can range from 10 to 40 young, born in late summer.
Venom Profile
The venom contains mild neurotoxins and proteolytic enzymes typically ineffective on humans; generally considered non-venomous to people.
Look-alikes
Ribbon Snakes (Thamnophis saurita) which are more slender with higher lateral stripes, and Dekay's Brownsnakes (Storeria dekayi) which lack the distinct longitudinal stripes and have different markings.
Conservation Status
IUCN Red List: Least Concern. Populations are stable, though local declines occur due to habitat loss and pesticide use affecting their prey.
Cultural Significance
One of the most frequently encountered snakes by the public; serves a vital ecological role in controlling pest populations like slugs and insects. Often kept as a 'starter snake' for hobbyists.
Notable Features
Garter snakes have a remarkable tolerance for cold and are often the first snakes to emerge in spring. Some populations are known to be resistant to the tetrodotoxin (TTX) found in the skin of newts they consume.