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 subarctic regions in Canada to the southernmost tip of Florida, and from the Atlantic coast to the Pacific coast.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Technically mildly venomous (opisthoglyphous/rear-fanged), but harmless to humans due to the inefficiency of the delivery system and low toxicity to mammals.
Danger Level
Harmless/Low Risk. Bites are rare and usually only occur when the animal is handled or harassed. Effects on humans are typically limited to minor local swelling or itching.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
IUCN Red List: Least Concern. The species is highly resilient and widespread, though local populations are threatened by habitat loss and pesticide use affecting their prey.
Physical Description
Greenish-brown to black ground color with three distinctive longitudinal yellow or cream stripes (one dorsal, two lateral). Between the stripes is a checkered pattern of black spots. Scales are keeled (ridged). Round pupils and a head that is slightly wider than the neck.
Size & Dimensions
The specimen in the image appears to be a juvenile or small adult, approximately 12-18 inches (30-45 cm). This species typically ranges from 18 to 26 inches, with maximum records around 4 feet (120 cm).
Habitat
Highly adaptable, found in a variety of environments including meadows, marshes, woodlands, hillsides, and suburban gardens. Often found near water sources like ponds, streams, or wetlands. This specimen is seen in a berry bush, illustrating its semi-arboreal hunting capability.
Behavior & Temperament
Primarily diurnal. When threatened, they may flatten their heads, strike defensively, or release a foul-smelling musk from their cloaca. They are generally shy and prefer to flee when encountered.
Diet & Feeding
Diet consists of earthworms, slugs, snails, frogs, toads, tadpoles, small fish, and occasionally small rodents or birds. They are active foragers rather than ambush hunters.
Reproduction
Ovoviviparous (giving birth to live young). Litters are typically large, ranging from 10 to 40 young, although record litters of over 80 have been documented. Breeding occurs in early spring.
Venom Profile
The venom contains mild neurotoxins and proteolytic enzymes used to subdue small prey like amphibians and fish. It is not medically significant to humans.
Look-alikes
Commonly confused with Ribbon Snakes (Thamnophis saurita), which are slenderer with the lateral stripe on scale rows 3 and 4, whereas Garter Snakes have it on rows 2 and 3. Also confused with Dekay's Brownsnakes.
Conservation Status
IUCN Red List: Least Concern. The species is highly resilient and widespread, though local populations are threatened by habitat loss and pesticide use affecting their prey.
Cultural Significance
A staple of North American backyard ecology, they are beneficial for pest control. They are often the first snake children encounter, making them important for ecological education and overcoming ophiophobia.
Notable Features
One of the few snakes that can safely consume toxic amphibians like newts or American Toads by sequestering or neutralizing their toxins. They are also known for forming large communal hibernating dens (hibernacula) in northern climates.