Overview
The Western Terrestrial Garter Snake (Thamnophis elegans), commonly known throughout mountain regions as the Wandering Garter Snake, is one of the hardiest and most ecologically adaptable reptiles in western North America. Found from arid desert sagebrush basins to chilly alpine meadows nearly 13,000 feet above sea level, this non-venomous colubrid is an active, diurnal hunter equally at home swimming in mountain lakes or hunting rodents on dry hillsides.
Biology and Physical Characteristics
Thamnophis elegans features an elongated, slender body with heavily keeled scales. Its coloration is highly variable but typically consists of a dark grey, olive-brown, or charcoal background accented by a distinct bright yellow or pale cream vertebral stripe running down its spine and two paler lateral stripes. Its flanks are patterned with a subtle checkerboard of dark spots, and its belly is pale yellowish-green.
Behavior and Ecology
An opportunistic predator with remarkable dietary flexibility, it hunts both aquatic prey (fish, tadpoles, and leeches in mountain streams) and terrestrial animals (voles, mice, lizards, and slugs in meadow grasses). Females are viviparous (live-bearing), giving birth in late summer to clutches of 8 to 20 fully formed, active young that immediately hunt insects and small slugs.
Conservation and Human Impact
Classified as Least Concern by the IUCN, the Western Terrestrial Garter Snake is exceptionally widespread and common throughout western national parks like Yellowstone, Yosemite, and Grand Teton. It faces localized threats from road mortality and the introduced fungal pathogen Ophidiomyces ophiodiicola (snake fungal disease).
Interesting Factoid
The Western Terrestrial Garter Snake is a high-altitude champion; it can thrive in chilly Rocky Mountain meadows at nearly 13,000 feet elevation, where morning temperatures plunge near freezing even in mid-summer.