Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Widely distributed across North America. Found from the Atlantic to the Pacific coasts and from Subarctic regions of Canada to the Southern United States.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous (rear-fanged/opisthoglyphous); however, they lack a delivery system efficient enough to harm humans.
Danger Level
Harmless / Low Risk. Bites may cause mild swelling or itching in rare cases of allergic reaction, but they are not dangerous to humans or pets.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
Least Concern (IUCN). Extremely common and adaptable, though localized populations face threats from habitat loss and pesticide use.
Physical Description
Slender body with a head slightly wider than the neck. Large, round pupils. The dorsal color is variable (gray, brown, or green) typically featuring three longitudinal stripes (cream, yellow, or greenish). Supralabial scales are usually light and unmarked.
Size & Dimensions
Specimen in photo appears to be an adult or sub-adult based on head proportions. Typically range from 18 to 26 inches (46–66 cm), but can reach up to 4 feet (122 cm).
Habitat
Generalist species found in forests, fields, prairies, and suburban backyards. They have a strong preference for damp environments near water sources like marshes, lakes, or streams.
Behavior & Temperament
Diurnal and active. Generally shy and will flee if approached. When cornered, they may flatten their bodies, strike (often with a closed mouth), or release a foul-smelling musk from their cloaca.
Diet & Feeding
Highly varied diet including earthworms, slugs, frogs, toads, salamanders, and occasionally small fish or rodents. They are active foragers that swallow prey alive.
Reproduction
Ovoviviparous (gives birth to live young). Litters are typically large, ranging from 10 to 40 neonates, born in late summer.
Venom Profile
The saliva contains mild neurotoxins that help immobilize small prey like amphibians. Non-medically significant to humans.
Look-alikes
Often confused with Ribbon Snakes (Thamnophis saurita), which are more slender with longer tails and lack markings on the labial scales, or Dekay's Brownsnakes (Storeria dekayi).
Conservation Status
Least Concern (IUCN). Extremely common and adaptable, though localized populations face threats from habitat loss and pesticide use.
Cultural Significance
One of the most well-known snakes in North America. They play a vital ecological role in controlling pest populations (slugs and insects) and serve as a prey source for birds of prey.
Notable Features
Remarkable for their high cold tolerance, being among the first snakes to emerge from brumation in spring. Some populations have evolved a resistance to the toxins of rough-skinned newts.