NOTABLE RARE AND ENDANGERED SPECIES IN THE GATEWAY VALLEY

photo by Marguerite Gregory, 1958

Red-Legged Frog
(Rana aurora draytonii)
Federal Status: Threatened
Mark Twains celebrated jumping frog of Calaveras County was probably a red-legged frog, making its first splash into fame. The largest native frog in the western United States, its length ranges from 1.5 to 5.1 inches. Adults have largely red abdomens and hind legs; their backs exhibit small black flecks and larger irregular dark blotches on a brown, gray, olive, or reddish background color. This mighty-legged frog used to inhabit Point Reyes and Redding southward to northwestern Baja California, Mexico.

Yet the frog has dwindled out in Calaveras County and, indeed, in most of the state. By 1970, red-legged frogs had disappeared from virtually every creek in the Sierra Nevada, Central Valley, and Southern California. Although it remains, struggling, in the Bay Area, according to the U.S. Fish and Wildlife Service the frog has been extirpated from 70 percent of its former range. This disappearance exemplifies a general amphibian decline throughout the state. Within its remaining range, the red-legged frog is threatened by a wide variety of human impacts, including urban encroachment, construction of reservoirs and water diversions, introduction of exotic predators (such as the bullfrog) and competitors, livestock grazing, and habitat fragmentation.

The red-legged frogs fleshy size, unfortunately, contributed to its decline. The fat red hind legs that lifted the frog so easily into the air in front of the prospectors eyes, notes the FWS, soon became a fatal liability. Californias numerous new residents had a taste for frog legs and harvested red-legged frogs wherever they were to be found, first around the San Francisco Bay and then in the Central Valley.

Other significant species include the elusive and elegant Alameda whipsnake, and rare native plants including the Oakland star tulip and the flowering western leatherwood.

On October 3, 2000, the U. S. Fish and Wildlife Service finalized designation of "critical habitat" pursuant to the Endangered Species Act for the imperiled Alameda whipsnake. 406,598 acres of land in Contra Costa, Alameda, San Joaquin, and Santa Clara Counties have been identified as habitat critical for the recovery of the threatened whipsnake. The designation follows settlement of a lawsuit brought against FWS in November 1999 by the Center for Biological Diversity. The critical habitat protections went into effect November 1, 2000.

The whipsnake, listed as a threatened species under the ESA in December 1997, occupies northern coastal scrub and chaparral habitats primarily in Contra Costa and Alameda Counties. Whipsnake habitat has been severely reduced and fragmented by urban sprawl, road construction, livestock grazing, and fire suppression.

The whipsnake is a slender snake with black dorsal coloring and distinctive yellow-orange racing stripes down each side. Adults grow from three to four feet in length. The Alameda whipsnake is extremely fast moving and holds its head high off the ground in a cobra-like manner while hunting for potential prey, which includes lizards, small mammals, snakes, and nesting birds. Whipsnakes occupy a home range from 5 to 20 acres and can move up to a mile while traversing their territories. The whipsnake utilizes coastal scrub and chaparral for cover, adjacent grassland as foraging habitat, and rock outcrops for basking to regulate its body temperature.

The ESA defines critical habitat as the "areas essential for the survival and recovery of species." Federal agencies may not authorize, permit, or fund projects which destroy or "adversely modify" critical habitat for a listed species. Many proposed developments in whipsnake habitat need federal permits from the U. S. Army Corps of Engineers and the critical habitat designation will require consultation with FWS to evaluate their impact on the snake's habitat. Urban development and major highways have fragmented the whipsnake into five remaining population centers: (1) Sobrante Ridge, Tilden/Wildcat Regional Parks area to Briones Hills, in Contra Costa County (Tilden-Briones population); (2) Oakland Hills, Anthony Chabot area to Las Trampas Ridge, in Contra Costa County (Oakland-Las Trampas population); (3) Hayward Hills, Palomares area to Pleasanton Ridge, in Alameda County (Hayward-Pleasanton Ridge population); (4) Mount Diablo vicinity and the Black Hills, in Contra Costa County (Mount Diablo-Black Hills population); and (5) Wauhab Ridge, Del Valle area to the Cedar Mountain Ridge, in Alameda County (Sunol-Cedar Mountain population).

Gateway Valley is a vital link in the wildlife corridor connecting the Tilden/Briones areas with the Chabot/Las Trampas lands.