Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: T. sirtalis
North America, ranging from the Atlantic to the Pacific coasts, spanning across southern Canada down through the United States into parts of Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: T. sirtalis
Conservation
IUCN Red List status is Least Concern, though localized populations face threats from habitat fragmentation, road mortality, and intentional killing.
Physical Description
Slender body with a dark greyish-brown background overlaid with a complex pattern of dark spots and checkering, a distinct head shape with light labial markings, and notable cloudy blue-tinted eyes indicating an upcoming molt (ecdysis). Scales are keeled.
Size & Dimensions
Estimated specimen length is approximately 30-45 cm (juvenile). Typical adults reach total lengths of 46 to 137 cm.
Habitat
Found in a diverse range of habitats including forests, fields, grasslands, marshes, and near the edges of water bodies such as streams, ponds, and ditches, from sea level up to high elevations.
Diet & Feeding
Active forager feeding primarily on amphibians, earthworms, small fish, and occasionally small rodents or insects, captured live and swallowed whole.
Reproduction
Viviparous species, giving birth to live young. Mating typically occurs in the spring shortly after emerging from hibernation, yielding litters ranging from 10 to 40 or more offspring.
Look-alikes
Frequently confused with other natricine snakes like water snakes (Nerodia species) and other garter snake species (Thamnophis spp.), distinguished primarily by specific dorsal and lateral stripe patterns and scale counts.
Conservation Status
IUCN Red List status is Least Concern, though localized populations face threats from habitat fragmentation, road mortality, and intentional killing.
Cultural Significance
Often encountered in suburban areas and popular in educational settings due to their adaptability, serving a key ecological role in controlling amphibian and invertebrate populations.
Notable Features
Exhibits a clear opaque blue eye condition known as 'spectacle' clouding, which happens naturally prior to shedding the skin, temporarily impairing vision.