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, and from the subarctic regions of Canada to the southern United States, including most of the lower 48 states.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Harmless / Mildly venomous (Rear-fanged/Opisthoglyphous)
Danger Level
Harmless/Low Risk. Bites may cause minor localized swelling or itching in sensitive individuals, but they are not medically significant to 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 water pollution affecting prey species.
Physical Description
Slender body with three longitudinal stripes; one dorsal and two lateral. Colors vary widely but are typically olive, brown, or black with yellow, greenish, or bluish 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 18-24 inches long. Typical size range for species is 18 to 54 inches (46 to 137 cm).
Habitat
Extremely versatile; found in meadows, marshes, woodlands, and hillsides. They show a strong preference for being near water sources, such as ponds, lakes, streams, and ditches, from sea level to high mountain elevations.
Behavior & Temperament
Diurnal and active forager. When threatened, they may discharge a foul-smelling musk from their cloaca, flatten their heads to appear larger, or strike. Generally shy and will flee if given the chance.
Diet & Feeding
Generalist carnivores. Diet includes earthworms, amphibians (frogs, toads, salamanders), small fish, leeches, and occasionally small mammals or birds. They swallow prey whole without constriction.
Reproduction
Ovoviviparous (gives birth to live young). Litters typically range from 10 to 40 individuals, though larger litters have been recorded. Mating usually occurs in early spring shortly after emerging from brumation.
Venom Profile
Neurotoxic; produces a mild toxin in the Duvernoy's gland which is effective on small prey but lacks a delivery system capable of harming humans.
Look-alikes
Ribbon Snakes (Thamnophis saurita) which are more slender with stripes on higher scale rows; Garter Snakes have stripes on rows 2 and 3. Also confused with DeKay's Brownsnakes which lack the distinct longitudinal stripes.
Conservation Status
IUCN Red List: Least Concern. Populations are stable, though local declines occur due to habitat loss and water pollution affecting prey species.
Cultural Significance
One of the most commonly encountered snakes in North America, often serving as an introductory species for budding naturalists. They play a vital ecological role in controlling pest populations and are important links in the food web.
Notable Features
Highly cold-tolerant; they are often the first snakes to emerge in spring. Some populations in the Pacific Northwest have evolved a resistance to the tetrodotoxin found in the skin of Newts, their preferred prey.