Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: sirtalis
North America, ranging from subarctic regions of Canada through most of the continental United States (excluding parts of the Southwest) to Northern Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous (opisthoglyphous/rear-fanged), but generally considered harmless to humans.
Danger Level
Harmless/Low Risk. Bites may cause localized swelling or itching in sensitive individuals, but the snake is not capable of delivering life-threatening venom.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: sirtalis
Conservation
Least Concern (IUCN). They are one of the most common and widely distributed snake species in North America.
Physical Description
Characterized by three longitudinal yellow or cream-colored stripes on a dark green, brown, or black ground color. The head is slightly wider than the neck, with large eyes and round pupils. Scales are keeled (ridged).
Size & Dimensions
The specimen in the image appears to be an adult, approximately 18-24 inches. The species typically ranges from 18 to 36 inches, with a record maximum around 54 inches.
Habitat
Extremely versatile; found in meadows, marshes, woodlands, and suburban gardens. They prefer areas near water but are frequently found in terrestrial microhabitats like leaf litter and under logs.
Behavior & Temperament
Diurnal and active. 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 chance.
Diet & Feeding
Generalist carnivores; they consume earthworms, slugs, frogs, toads, salamanders, and small fish. They do not constrict; they use their mild venom and strong jaws to swallow prey alive.
Reproduction
Viviparous (gives birth to live young). Litters typically range from 10 to 40 neonates, born in late summer or early autumn.
Venom Profile
The venom contains a mild neurotoxin that is effective on small prey like amphibians and fish, but it is not medically significant to humans.
Look-alikes
Ribbon Snakes (Thamnophis saurita) are thinner with stripes on different scale rows; Water Snakes (Nerodia spp.) are much heavier-bodied and lack the distinct longitudinal stripes.
Conservation Status
Least Concern (IUCN). They are one of the most common and widely distributed snake species in North America.
Cultural Significance
Highly beneficial in gardens for pest control, specifically for managing slug and rodent populations. They are often a 'starter' snake for budding naturalists due to their abundance.
Notable Features
Garter snakes are one of the few predators capable of consuming toxic amphibians, such as Rough-skinned Newts, due to an evolved resistance to tetrodotoxin.