Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Widely distributed across North America. Found in almost every US state (except the extreme Southwest), most of southern Canada, and parts of northern Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous (opisthoglyphous/rear-fanged); however, they are generally considered harmless to humans as their delivery system is inefficient for large mammals.
Danger Level
Harmless/Low Risk. Bites are rare and usually only occur when the snake is handled or stepped on. They possess no medical threat to healthy 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 base.
Physical Description
Highly variable, typically dark green, brown, or black with three prominent longitudinal yellow, orange, or cream stripes (one dorsal, two lateral). Red or black checkers may appear between stripes. Head is slightly wider than the neck; eyes have round pupils; scales are keeled.
Size & Dimensions
The specimen in the image appears to be an adult approximately 18-24 inches long. The species typical range is 18 to 35 inches (46-89 cm), with maximums reaching 50 inches.
Habitat
Extremely versatile; found in woodlands, meadows, marshes, and suburban gardens. Prefers proximity to water but can survive in relatively dry upland areas. Elevation range from sea level to alpine meadows.
Behavior & Temperament
Diurnal and active forager. Generally docile but will flatten its head, strike, or release a foul-smelling musk (and sometimes feces) from the cloaca when threatened. Often found basking in sunny patches.
Diet & Feeding
Generalist carnivore. Preys on earthworms, slugs, frogs, toads, salamanders, fish, and occasionally small rodents or birds. Uses active foraging to hunt and swallows prey alive.
Reproduction
Ovoviviparous (gives birth to live young). Litters typically range from 10 to 40 young, born in late summer or early autumn after a spring mating season.
Venom Profile
Neurotoxic and proteolytic components. Causes paralysis in small prey like frogs and fish. In humans, it usually causes only localized swelling or itching.
Look-alikes
Ribbon Snakes (Thamnophis saurita) which are more slender with stripes on different scale rows; Linnaeus's DeKay's Brownsnake (Storeria dekayi) which lacks the high-contrast stripes and has different spotting.
Conservation Status
IUCN Red List: Least Concern. Populations are stable, though local declines occur due to habitat loss and pesticide use affecting their prey base.
Cultural Significance
One of the most frequently encountered snakes by homeowners. Valued by gardeners for controlling pests like slugs and insect larvae. Significant in ecological studies due to their resistance to toxic newts (Taricha).
Notable Features
Highly cold-tolerant; they are often the first snakes to emerge in spring and last to hibernate. Famous for forming large 'mating balls' in certain northern populations (e.g., Narcisse, Manitoba).