The red-legged frog (Rana aurora) populations used to occur with great frequency throughout the state. The jumping frogs of Calavaras County (made famous by Mark Twain) were red-legged frogs. Early in the 20th century zoologists walking around Yosemite found three populations of red-legged frog. Today those populations cannot be found, and in fact the red-legged frog has suffered a catastrophic collapse in the Sierras and other areas of the state. As a result of these declines, the red-legged frog is now on the list of endangered species.
The last remaining substantial populations of the frog occur in Monterey County, Santa Barbara County, and San Luis Obispo County. Isolated populations of the frog still exist along the California coastline in places like Point Reyes, Suisun marsh, San Pedro Creek, Pescadero marsh, and other areas in San Mateo county.
One of the roles of the red-legged frog is as prey for the San Francisco Garter Snake (SFGS). Adult snakes feed primarily on the red-legged frog. So if a frog population collapses, any local SFGS populations will be affected, most likely negatively. Some research has shown that the SFGS cannot eat bullfrogs as easily as red-legged frogs.
How to identify: the red-legged frog grows up to five inches long, and has red on the underside of the back legs, as well as lower abdomen. The frog's back has splotches of brown or olive punctuated by black specks, often on skin which is loose and wrinkled. Immature frogs may have yellow instead of red.
Ironically one of the threats to the red-legged frog is the bullfrog, which was introduced in order to supply frog legs for local restaurants. The bullfrog eats the reg-legged frog's eggs, and usually takes over the red-legged frog's habitat. Development's impact on watersheds also negatively affects frogs.
Photos by Scott Woodruff
