Threatened or Endangered: Yes
Summary adapted text by from Don Roberson. Most who appreciate wildlife will agree that the San Francisco Garter Snake is California’s most beautiful snake. The bright orange head, combined with dazzling black and red stripes, is impressive enough, but the pale stripes and belly are washed with the most delicate turquoise. It is just a wonderful serpent.
It is also among California’s rarest snakes. It has been official designated as “endangered” on State lists since 1966, and was on the first Federal Endangered Species List established in 1973. Once common in stock ponds and small marshes in San Mateo County on the San Francisco Peninsula, it has been reduced to a mere handful due to urbanization, the draining and pollution of wetlands, and because its beauty makes it popular with illegal collectors. A recent population estimate was of ~1500 snakes. It has been completely extirpated from many areas it was once common (e.g., Skyline Road area along the ridge between the Pacific Ocean) and the remnant populations are now limited to a few wetlands near S.F. Airport; around Crystal Springs Reservoir; and locally along the San Mateo County coast from Pacifica to Pt. Año Nuevo. It has been recorded to Waddell Creek, one mile into northern Santa Cruz County, but for all practical purposes the sustainable populations are endemic to San Mateo County.
This garter snake is primarily a frog-eater, and thus it sticks close to water. Much of its remaining habitat is in small reedy marsh-edges and ponds. Note the many colors among the reeds (near right): green, rust, pale tan. Among this kaleidoscope the smallish snake (1 to 3 feet typically; maximum 4.25 feet) is amazingly well camouflaged. While the color pattern can be discerned among the grass at close range (far right; the snake is facing away), at any distance it just blends into the habitat. Eaton (2002) thought the bright patterns might be a warning to predators, but perhaps the opposite is true: the crisply patterned colors fit the snake’s preferred habitat and hide it from predators. Only when the ponds dry up in late summer does it move into uplands, spending the winter in small mammal burrows.
Range of the San Francisco Garter Snake: Contrary to its name, the San Francisco Garter snake (SFGS) was historically found wholly within San Mateo County lines. This small range has been steadily reduced over the years by human development and habitat reduction. One of the larger blows to its population was the development of the Skyline Ponds “sag” ponds along Skyline Boulevard in the post World War II housing boom. In the 1940’s these ponds were home to “hundreds” of individuals. By the 1960’s nearly all of these ponds had been drained and developed. By 1966, scientists were concerned enough to list it as one of the first endangered species. Currently, San Francisco garter snake’s are found only in a few isolated locations within their former range. Laguna Salada, owned by the City of San Francisco’s Sharp Park golf course and adjacent Mori Point are one of them.
Other Facts: Although the San Francisco garter snake is considered beneficial to humans, preying on pests such as small mammals, reptiles, and amphibians, they are not to be approached upon sighting. When threatened, they excrete foul smells from their anal glands and often empty their bowels on unsuspecting captors. Nonetheless, these endangered creatures are quickly losing ground, and with only five populations left, need the help of humans to protect their few remaining habitats.