With its white, black, and orange-red dorsal stripes, bright turquoise belly, and orange-red head--not to mention its red tongue and black lips--the San Francisco garter snake (Thamnophis sirtalis tetrataenia) is considered one of the most beautiful snakes in North America, if not the world. How wonderful to have such a creature in our midst!
Yet it has another distinction, one not so wonderful: through human actions over the decades, it has become one of the most endangered snakes on the continent. Declared endangered in 1967 by the federal government--one of the first species to be listed under the new Endangered Species Act--and in 1971 by the State of California, this shy reptile has steadily lost habitat to land development and pollution, and its beauty has led to illegal poaching by collectors. Today, with a population estimated at less than 1,500, the San Francisco garter snake can rarely be seen anywhere but in a zoo.
As if that weren’t enough, its favorite prey, the California red-legged frog (Rana aurora draytonii)--the largest frog west of the Continental Divide, made famous by Mark Twain’s story--is also endangered, because of habitat loss and competition from and predation by nonnative bullfrogs.
Historically, the snake and its froggy food were found in scattered marshes and ponds on both flanks of the Santa Cruz Mountains. (The snake’s name is actually a misnomer, since its range is limited to San Mateo County.) Beginning in the 1940s and into the 1960s, however, when “sag ponds” along Skyline Boulevard, formed by movement of the San Andreas Fault, were drained to make way for people, these animals were squeezed out. Today they are left only in small pockets near San Francisco Airport and around Crystal Springs Reservoir, and locally in coastal wetlands including Pescadero Marsh, Año Nuevo State Reserve, and Mori Point in Pacifica.
Although there’s not much critical habitat left to protect, the good news is that what little remains is getting active help. At Mori Point, the newest unit of Golden Gate National Recreation Area, the nonprofit Golden Gate National Parks Conservancy (GGNPC) has been working hard to give the San Francisco garter snake a leg-up (so to speak). Last year, the park and the conservancy kicked off a habitat restoration and trail improvement project that is intended in large part to help the beautiful reptile.