Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Venomous Status
Mildly venomous (Rear-fanged/Opisthoglyphous); they possess a Duvernoy's gland.
Danger Level
Harmless/Low Risk; bites may cause minor localized swelling or itching in sensitive individuals, but they are not dangerous to humans.
Geographic Range
Widely distributed across North America, ranging from the subarctic regions of Canada to the Southern United States, and from the Atlantic coast to the Pacific coast.
Conservation Status
Least Concern (IUCN); widespread and abundant, though local populations can be affected by habitat loss and pollution.
Physical Description
Features a dark background color (black or brown) with three prominent longitudinal yellow, whitish, or greenish stripes: one dorsal and two lateral. The head is wider than the neck, eyes are large with round pupils, and the scales are heavily keeled.
Size & Dimensions
The specimen in the image appears to be an adult, approximately 18–26 inches long. The species typically ranges from 18 to 54 inches (46–137 cm) in total length.
Habitat
Highly adaptable; found in meadows, marshes, woodlands, and hillsides. They have a strong preference for being near water sources such as ponds, streams, and lakes. Found from sea level to high mountain elevations.
Behavior & Temperament
Primarily diurnal. When threatened, they may flatten their bodies to appear larger, release a foul-smelling musk from their cloaca, or strike defensively. Generally timid and prefers flight over fight.
Diet & Feeding
Generalist carnivore; feeds on earthworms, amphibians (frogs, toads, salamanders), fish, and occasionally small rodents or birds. They are active foragers that swallow prey alive without constriction.
Reproduction
Viviparous (gives birth to live young). Breeding occurs in spring shortly after emerging from brumation. Litters are large, typically ranging from 10 to 40 neonates born in late summer.
Venom Profile
Venom Type
Mildly neurotoxic and proteolytic, but lacks a sophisticated delivery system to pose a threat 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 different scale rows; also Lined Snakes (Tropidoclonion lineatum) which have a double row of black spots on the belly.
Conservation Status
Least Concern (IUCN); widespread and abundant, though local populations can be affected by habitat loss and pollution.
Cultural Significance
One of the most frequently encountered snakes in North America; plays a vital role in controlling pest populations and serves as a key indicator species for wetland health.
Notable Features
Remarkable for their high resistance to Tetrodotoxin (TTX) found in Pacific newts, allowing them to consume prey that is lethal to most other predators.