Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Widely distributed throughout North America, ranging from the subarctic regions of Canada to the Gulf Coast of Mexico, and from the Atlantic to the Pacific coasts.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous (Opisthoglyphous/Rear-fanged); however, the delivery system is inefficient and generally harmless to humans.
Danger Level
Harmless/Low Risk; they are non-aggressive toward humans and their bite is medically insignificant unless a rare allergic reaction occurs.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
Least Concern (IUCN); very stable population, though localized populations face threats from habitat loss and pesticide use.
Physical Description
Slender body with three longitudinal stripes (one dorsal, two lateral) which are typically cream, yellow, or greenish against a dark background of black, brown, or olive. Features a distinct checkered pattern between stripes and keeled (rough) scales. The head is wider than the neck with large eyes and round pupils.
Size & Dimensions
The specimen appears to be a juvenile/sub-adult, roughly 10-15 inches long. Adults typically range from 18 to 26 inches, with maximum records around 4 feet.
Habitat
Versatile habitat generalist found in woodlands, meadows, marshes, and suburban gardens. Prefers proximity to water sources but can be found far from them; occurs from sea level to high mountain elevations.
Behavior & Temperament
Diurnal and active. Highly defensive when cornered, often emitting a foul-smelling musk from cloacal glands and occasionally flattening their heads to appear larger. Otherwise, they are shy and quick to flee.
Diet & Feeding
Generalist carnivore feeding on earthworms, amphibians (frogs/toads), slugs, small fish, and occasionally small rodents or birds. They use active foraging rather than constriction.
Reproduction
Ovoviviparous (bears live young). Mating occurs in spring shortly after emergence from brumation. Females produce litters of 10 to 40 young in late summer.
Venom Profile
Mildly neurotoxic and proteolytic but lacks a specialized delivery system; it may cause localized swelling or itching in sensitive individuals.
Look-alikes
Ribbon Snakes (Thamnophis saurita) which are more slender with stripes on scale rows 3 and 4; Lined Snakes (Tropidoclonion lineatum) which have a double row of black spots on the belly; and various species of Water Snakes (Nerodia spp.).
Conservation Status
Least Concern (IUCN); very stable population, though localized populations face threats from habitat loss and pesticide use.
Cultural Significance
One of the most commonly encountered snakes in North America; plays a vital role in controlling pest populations of slugs and insects in gardens and ecosystems.
Notable Features
Remarkable for their high tolerance to cold temperatures and their ability to safely consume certain toxic amphibians (like Rough-skinned Newts) that would kill other predators.