Common Garter Snake
Thamnophis sirtalis • Order: Squamata; Suborder: Serpentes; Family: Colubridae; Subfamily: Natricinae; Genus: Thamnophis; Species: sirtalis
Extensive range across North America, from the Atlantic to the Pacific coast, and from subarctic regions of Canada to the Rio Grande in Mexico. Exceptions include some arid regions of the Southwest.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Mildly venomous (rear-fanged/Duvernoy's gland), but generally considered harmless to humans. Fangs are enlarged posterior maxillary teeth.
Danger Level
Harmless/Low Risk. Not a threat to humans or pets; they are shy and prefer to flee. Bites are rare and usually only occur if the snake is handled roughly.
Family
Order: Squamata; Suborder: Serpentes; Family: Colubridae; Subfamily: Natricinae; Genus: Thamnophis; Species: sirtalis
Conservation
IUCN Status: Least Concern. Very common and widespread, though local populations face threats from habitat loss and pesticide use.
Physical Description
Dark brown or black base color with three distinctive longitudinal yellow, green, or white stripes. Keeled scales give a textured appearance. Head is slightly wider than the neck with large eyes and round pupils. A checkerboard pattern of black spots is often visible between the stripes.
Size & Dimensions
Specimen in image appears to be an adult approximately 45-60 cm long. Typical adult range is 46 to 137 cm. Females are generally larger than males.
Habitat
Highly adaptable generalist found in meadows, marshes, woodlands, and suburban gardens. Primarily terrestrial but often found near water sources like ponds or streams. Elevation range from sea level up to 2,500+ meters.
Behavior & Temperament
Diurnal and active. Most active in the morning or late afternoon during summer. If threatened, they may flatten their bodies to appear larger, strike without biting, or more commonly, release a foul-smelling musk from their cloaca.
Diet & Feeding
Generalist carnivore. Common prey includes earthworms, slugs, frogs, toads, salamanders, fish, and occasionally small birds or rodents. They use active foraging to locate prey.
Reproduction
Ovoviviparous (gives birth to live young). Breeding occurs in spring shortly after emerging from hibernation. Litters can range from 10 to 40 young, born in late summer or early autumn.
Venom Profile
Mild neurotoxic components primarily effective on small prey like amphibians. Non-medically significant for humans, potentially causing mild swelling or itching.
Look-alikes
Commonly confused with Ribbonsnakes (Thamnophis saurita), which are more slender with longer tails, and Plains Garter Snakes (Thamnophis radix), which have a lighter stripe on the side located on scale rows 3 and 4.
Conservation Status
IUCN Status: Least Concern. Very common and widespread, though local populations face threats from habitat loss and pesticide use.
Cultural Significance
One of the most widely recognized snakes in North America. They play a vital ecological role by controlling pest populations like slugs and insects and are often the first snake children encounter in nature.
Notable Features
Remarkable for their extreme cold tolerance, being among the northernmost ranging snakes. They are known for 'brumating' in large communal dens containing hundreds or even thousands of individuals in northern climates.