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 to the southernmost tip of Florida and parts of Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Harmless / Mildly venomous (contains Duvernoy's gland), considered non-venomous to humans. Aglyphous (lacking specialized fangs).
Danger Level
Harmless. Bites may cause localized itching or slight swelling in rare cases of allergic reactions, but they possess no threat to human life.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
IUCN Red List: Least Concern. The species is highly adaptable and widespread, though local populations may face threats from habitat loss and pollution.
Physical Description
Variable coloration but typically features three longitudinal stripes (yellow, green, or blue) on a dark background. Scales are keeled. The head is slightly wider than the neck, and pupils are round. This specimen shows a dark eye stripe and checkered pattern between stripes.
Size & Dimensions
Average adult length ranges from 18 to 26 inches (46 to 66 cm), with maximum records reaching 4 feet. This specimen appears to be a mid-sized adult.
Habitat
Generalist species found in a wide variety of habitats including forests, grasslands, and marshes. Highly associated with water sources and often found in suburban gardens, meadows, and near ponds/streams.
Behavior & Temperament
Diurnal and active. Generally shy and will flee if approached. If cornered, they may flatten their heads, strike, or release a foul-smelling musk from the cloaca.
Diet & Feeding
Carnivorous generalists that feed primarily on earthworms, amphibians (frogs, toads, salamanders), fish, and occasionally small rodents or birds. They use active foraging and swallow prey alive.
Reproduction
Viviparous (gives birth to live young). Mating occurs in spring shortly after emergence from brumation. Litters can range from 10 to 40 young, typically born in late summer.
Venom Profile
Mildly neurotoxic saliva; generally harmless to humans, only affecting small prey like amphibians and fish.
Look-alikes
Commonly confused with Ribbon Snakes (Thamnophis saurita) which are more slender with stripes on higher scale rows, and Lined Snakes (Tropidoclonion lineatum) which have a double row of black spots on the belly.
Conservation Status
IUCN Red List: Least Concern. The species is highly adaptable and widespread, though local populations may face threats from habitat loss and pollution.
Cultural Significance
Often the first snake encountered by children and gardeners, serving as a primary biological control for garden pests like slugs and insects. It is ecologically vital as both a predator and prey.
Notable Features
Highly cold-tolerant; some populations are known to hibernate in communal hibernacula containing thousands of individuals. They are also known for their resistance to tetrodotoxin found in newts.