Reptiles
Giant Garter Snake
Thamnophis gigas · also called giant garter snakes
Gliding through an irrigation canal bordering a Central Valley rice field, a giant garter snake makes use of the closest substitute it has left for the vast native marshes its ancestors once depended on, most of which disappeared under farmland generations ago.
Overview
The giant garter snake, Thamnophis gigas, is the largest species within the garter snake genus, found exclusively within wetland habitat in California’s Central Valley. Its severe historical habitat loss and current reliance on agricultural wetlands such as rice fields and irrigation canals make it one of the more conservation-significant reptiles in California.
A species surviving on borrowed habitat
With over 90 percent of its native marshland gone, the giant garter snake has had to make do with a landscape reshaped entirely for farming, finding refuge in canals and rice fields that happen to offer just enough water to get by.
Status
Vulnerable, federally threatened — confined to California’s Central Valley, surviving mainly in agricultural wetlands after severe historical loss of native marsh habitat.
Giant Garter Snake: common questions
Why is the giant garter snake threatened?
The giant garter snake has been federally listed as threatened because California's Central Valley, its only native range, has lost over 90 percent of its original wetland habitat to agricultural and urban development, forcing the species to survive largely within substitute habitat such as irrigation canals and rice fields.
How does the giant garter snake compare in size to other garter snakes?
The giant garter snake is the largest species within the garter snake genus, reaching a greater total length than most of its more widespread relatives, a size distinction reflected directly in its common name.
Why does the giant garter snake rely on rice fields and canals?
A giant garter snake now survives largely within irrigation canals, rice fields, and other agricultural wetland habitat because so much of its original natural marsh habitat within California's Central Valley has been converted to farmland, leaving these managed water systems as some of the only remaining suitable wetland habitat available.
Where does the giant garter snake live?
The giant garter snake is native exclusively to wetland habitat within California's Central Valley, making it endemic to this single region and found nowhere else in the world.