Common Garter Snake
Thamnophis sirtalis • Order: Squamata; Suborder: Serpentes; Family: Colubridae; Subfamily: Natricinae; Genus: Thamnophis; Species: T. sirtalis
Widely distributed across North America. Found in most of the continental United States (excluding parts of the Southwest), southern Canada, and isolated populations in Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Venomous (Mildly); specifically, they possess a primitive Duvernoy's gland. They are often classified as non-venomous in practical terms because they lack fangs and their venom is harmless to humans.
Danger Level
Harmless; they pose no threat to humans or pets. Bites are rare and usually only occur if the snake is handled roughly or pinned.
Family
Order: Squamata; Suborder: Serpentes; Family: Colubridae; Subfamily: Natricinae; Genus: Thamnophis; Species: T. sirtalis
Conservation
IUCN Status: Least Concern. Populations are stable and they are one of the most common snake species in North America.
Physical Description
Characterized by a dark background color (black, brown, or olive) with three longitudinal yellow, green, or blue stripes. The head is slightly wider than the neck, eyes are large with round pupils, and the dorsal scales are keeled (rough to the touch).
Size & Dimensions
The specimen in the image appears to be a juvenile or young adult, approximately 12-18 inches. Adults typically range from 18 to 26 inches, though large females can reach up to 4 feet.
Habitat
Extremely versatile; found in forests, grasslands, suburban gardens, and fields. They have a strong preference for being near water sources like ponds, streams, and marshes. They are found from sea level to high mountain elevations.
Behavior & Temperament
Diurnal and active forager. Generally timid and quick to flee. When cornered, they may flatten their heads, strike (often with a closed mouth), and release a foul-smelling musk from their cloaca as a defense mechanism.
Diet & Feeding
Generalist carnivore. Primarily feeds on earthworms, amphibians (toads, frogs, salamanders), small fish, and occasionally slugs or small rodents. They use their saliva to immobilize prey and swallow it whole.
Reproduction
Ovoviviparous (gives birth to live young). Mating occurs in spring shortly after emergence from hibernation. Females give birth to 10–40 young in late summer or early autumn.
Venom Profile
Mildly neurotoxic proteins that facilitate the capture of small prey like amphibians. Non-medically significant to humans; may cause localized swelling or itching in rare cases of allergic reaction.
Look-alikes
Ribbon Snakes (Thamnophis saurita) are thinner with more brilliantly colored stripes; DeKay's Brownsnakes (Storeria dekayi) lack the prominent longitudinal stripes and are usually smaller.
Conservation Status
IUCN Status: Least Concern. Populations are stable and they are one of the most common snake species in North America.
Cultural Significance
Commonly encountered in residential gardens, they are highly valued by gardeners for pest control (eating slugs and grasshoppers). They are frequently the first snake species encountered and identified by children.
Notable Features
Garter snakes are one of the few predators capable of eating toxic newts, having evolved a resistance to tetrodotoxin. They are also known for forming large communal 'mating balls' during the spring emergence.