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 through most of the United States to northern Mexico; it is one of the most widely distributed snake species on the continent.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Harmless / Mildly venomous (Duvernoy's gland). They lack fangs and possess a primitive delivery system in the rear of the jaw.
Danger Level
Harmless to Low Risk. They are not dangerous to humans or pets. Defensive bites may occur if the snake is handled or cornered but rarely break the skin significantly.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
Least Concern (IUCN). Highly adaptable to human-altered landscapes, though local populations can be affected by pesticide use and loss of wetlands.
Physical Description
Slender body with three longitudinal stripes: one down the center of the back and one on each side. Coloration is typically dark olive, brown, or black with yellowish or greenish stripes. Scales are keeled (ridged). The head is distinct from the neck with large eyes and round pupils.
Size & Dimensions
The specimen in the image appears to be a subadult or adult, approximately 18-24 inches (45-60 cm) long. Adults typically range from 18 to 26 inches, with a maximum record of about 49 inches.
Habitat
Extremely versatile, found in forests, fields, prairies, and suburban backyards; typically prefers areas near water such as marshes, ponds, and streams. They are found from sea level to high mountain elevations.
Behavior & Temperament
Diurnal and active forager. When threatened, they may flatten their heads, strike defensively, or release a foul-smelling musk from their cloaca. They are generally shy and will flee if given the opportunity.
Diet & Feeding
Generalist carnivore. Feeds on earthworms, slugs, frogs, toads, salamanders, fish, and occasionally small rodents. They use their keen sense of smell and sight to hunt and do not constrict their prey.
Reproduction
Ovoviviparous (gives birth to live young). Breeding occurs in the spring after emerging from hibernation. Females produce large litters, typically ranging from 10 to 40 young, born late summer or early fall.
Venom Profile
The venom is neurotoxic but mild; it is not considered medically significant to humans, though it can cause slight swelling or itching at the bite site.
Look-alikes
Commonly confused with Ribbon Snakes (Thamnophis saurita), which are more slender and have the lateral stripes on scale rows 3 and 4; or DeKay's Brownsnakes (Storeria dekayi), which lack the prominent dorsal stripe.
Conservation Status
Least Concern (IUCN). Highly adaptable to human-altered landscapes, though local populations can be affected by pesticide use and loss of wetlands.
Cultural Significance
One of the most recognized snakes in North America. They play a vital ecological role by controlling pest populations of slugs and insects and serve as a primary food source for birds of prey.
Notable Features
They are one of the few snake species that are resistant to the toxins of rough-skinned newts. They are also famous for hibernating in large communal dens called hibernacula, which can contain thousands of snakes.