Thamnophis sirtalis (Common Garter Snake)
Credit: Brad Shaffer
about the species
The common garter snake, Thamnophis sirtalis, is one of the most widespread species of North American snake and is native to much of the non-desert parts of the continental US. In California, this species includes three subspecies that constitute an ecological and geographical replacement series covering all of the state except the dry desert regions in southeastern California, the southern San Joaquin desert, and the highest elevations in the Sierra Nevada: Thamnophis sirtalis fitchi (Valley garter snake), Thamnophis sirtalis infernalis (California red-sided garter snake), and Thamnophis sirtalis tetrataenia (San Francisco garter snake). This species specializes on amphibian prey, both as larvae and adults. As such, it is intimately linked to both the ravaging amphibian declines in California and invasive bullfrogs that now constitute part of its prey base.
why species was selected
Although widespread, its populations are declining and it is a key conservation concern in the state: the San Francisco garter snake is federally and state listed as Endangered and the California red-sided garter snake is listed as a Species of Special Concern (SSC) from Ventura County south to the Mexican border, where it is all but extinct (Thomson 2016).
