Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Venomous Status
Mildly venomous (contains Duvernoy’s glands); effectively harmless to humans as they lack a delivery system for significant amounts of venom.
Danger Level
Harmless. While they may bite if provoked, it causes little more than minor irritation; however, they may release a foul-smelling musk when handled.
Geographic Range
Most of North America, from the Atlantic Coast to the Pacific Coast, and from subarctic regions of Canada to the Gulf Coast of Texas and northern Mexico.
Conservation Status
Least Concern (IUCN). Population is stable, though local declines occur due to habitat loss and pesticide use affecting their prey.
Physical Description
Dark brown or green base color with three distinct light-colored longitudinal stripes (yellow, green, or blue). One stripe runs down the center of the back, and two run along the sides. They have keeled scales and a relatively small, distinct head with large eyes and round pupils.
Size & Dimensions
The specimen appears to be an adult of approximately 18-24 inches. The typical species range is 18 to 54 inches (46 to 137 cm) in total length.
Habitat
Extremely adaptable; found in meadows, marshes, woodlands, hillsides, and suburban gardens. They prefer areas near water sources but can live in relatively dry environments.
Behavior & Temperament
Diurnal and active forager. They are generally shy and will flee if approached. If cornered, they may flatten their heads, strike defensively, or discharge musk from their cloaca.
Diet & Feeding
Generalist carnivore eating earthworms, slugs, snails, frogs, toads, salamanders, fish, and occasionally small rodents or birds using active foraging and quick strikes.
Reproduction
Ovoviviparous (gives birth to live young). Breeding occurs in spring; litters usually range from 10 to 40 young but can exceed 80 in large females.
Venom Profile
Venom Type
Mildly neurotoxic and proteolytic, primarily effective on small prey like amphibians and fish. Non-medically significant to humans.
AI-generated — see a qualified source if acting on this. For any snakebite, call emergency services immediately.
Look-alikes
Ribbon Snakes (Thamnophis saurita) which are more slender with stripes on higher scale rows; Plains Garter Snakes (Thamnophis radix); and Lined Snakes (Tropidoclonion lineatum).
Conservation Status
Least Concern (IUCN). Population is stable, though local declines occur due to habitat loss and pesticide use affecting their prey.
Cultural Significance
One of the most commonly encountered snakes by humans in North America, often serving as a child's first introduction to herpetology. They play a vital ecological role in controlling pest populations.
Notable Features
Remarkable for their cold tolerance, garter snakes can be found further north than almost any other North American reptile. Some populations are immune to the potent tetrodotoxin found in the skin of Newts (Taricha species).