Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: sirtalis
Widely distributed across North America, ranging from the Atlantic to the Pacific coasts and from subarctic regions of Canada to the Rio Grande in the southern United States and Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Technically mildly venomous; they possess a Duvernoy's gland which produces a mild neurotoxic secretion, delivered via enlarged posterior teeth (opisthodont).
Danger Level
Harmless/Low Risk; they do not pose a 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: sirtalis
Conservation
IUCN Status: Least Concern. Populations are stable, though they face local threats from habitat loss, pesticides, and road mortality.
Physical Description
Slender-bodied snake with three longitudinal stripes: one down the center of the back and one on each side. Stripes are typically yellow, cream, or greenish. The background color is dark olive, brown, or black. Scales are keeled (ridged). Head is slightly wider than the neck with large eyes and round pupils.
Size & Dimensions
Typically ranges from 18 to 39 inches (46–100 cm). This specimen appears to be an adult of approximately 24-30 inches in length.
Habitat
Generalist species found in forests, grasslands, and marshes. They are frequently found near water sources like ponds, streams, and wetlands, from sea level up to high mountainous elevations.
Behavior & Temperament
Diurnal and active forager. When threatened, they may flatten their heads, strike defensively (often with a closed mouth), or release a foul-smelling musk from their cloaca. They are generally shy and prefer to flee.
Diet & Feeding
Carnivorous generalists eating earthworms, slugs, snails, insects, fish, and amphibians (frogs and toads). They are resistant to the toxins in many toads (bufotoxins). They swallow prey alive without constriction.
Reproduction
Viviparous (gives birth to live young). Breeding occurs in spring shortly after emergence from brumation. Females give birth to 10–40 young in late summer or early autumn.
Venom Profile
Mild neurotoxic secretions; generally harmless to humans. It may cause mild localized swelling, itching, or irritation in some individuals.
Look-alikes
Often confused with Ribbon Snakes (Thamnophis saurita), which are more slender with stripes on higher scale rows, or Lined Snakes (Tropidoclonion lineatum), which have a double row of black spots on the belly.
Conservation Status
IUCN Status: Least Concern. Populations are stable, though they face local threats from habitat loss, pesticides, and road mortality.
Cultural Significance
One of the most commonly encountered snakes in North American gardens. They play a vital ecological role in controlling pest populations like slugs and insects.
Notable Features
Highly cold-tolerant; they are among the first snakes to emerge in spring. Some populations exhibit 'kleptothermy,' where many individuals huddle together in dens (hibernacula) to conserve heat during winter.