Species Profile
Giant Garter Snake
Species Details
Common NameGiant Garter Snake
Scientific NameThamnophis Couchi Gigas
Federal Listing StatusThreatened
Federal Regulating AgencyU.S. Fish and Wildlife Service
State Listing StatusThreatened (CA)
State Regulating AgencyCalifornia Department of Fish and Game
IUCN Red List StatusVulnerable A1cde+2cde (1996)
- Beach Lake Mitigation Bank
- Dolan Ranch Conservation Bank
- Gilsizer Slough South Giant Garter Snake Conservation Bank
- Liberty Island Conservation Bank
- Pope Ranch Conservation Bank
- Ridge Cut Farms Giant Garter Snake Conservation Bank
- Sutter Basin Conservation Bank

Species Range
The giant garter snake inhabits agricultural wetlands and other waterways such as irrigation and drainage canals, sloughs, ponds, small lakes, low gradient streams, and adjacent uplands in the Central Valley. Because of the direct loss of natural habitat, the giant garter snake relies heavily on rice fields in the Sacramento Valley, but also uses managed marsh areas in Federal National Wildlife Refuges and State Wildlife Areas. There have been only a few recent sightings of giant garter snakes in the San Joaquin Valley. Giant garter snakes are typically absent from larger rivers because of lack of suitable habitat and emergent vegetative cover, and from wetlands with sand, gravel, or rock substrates. Riparian woodlands typically do not provide suitable habitat because of excessive shade, lack of basking sites, and absence of prey populations. However, some riparian woodlands do provide good habitat.
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