They haven't been seen in the Santa Monica Mountains in four decades, but a population of California red-legged frogs in the neighboring Simi Hills is raising biologists' hopes that the threatened species might be able to be replanted in the rugged Southern California mountain range.
The frog species, best known for possibly inspiring Mark Twain's story the "Celebrated Jumping Frog of Calaveras County," has been declining in the century and a half since Twain set pen to paper. And its former habitat in Southern California is no exception. "California red-legged frogs haven't been spotted in the Santa Monica Mountains since the early 1970s," said Santa Monica Mountains National Recreation Area biologist Katy Delaney. "Our plan to bring them back here depends on the strength of this relatively tiny and isolated population in the Simi Hills."
The Simi Hills population in the Upper Las Virgenes Canyon Open Space Preserve is one of California's southernmost remaining populations of red-legged frogs. Only a population on the Santa Rosa Plateau near Temecula survives farther south.
46 of California's 58 counties -- including Calaveras -- once hosted populations of the threatened amphibian, known scientifically as Rana draytonii. Now, only 22 California counties host the frogs. Along with amphibian populations worldwide, numbers of the frog have been dropping for a range of reasons, mainly involving destruction of its habitat. Predation pressure from introduced bullfrogs and overconsumption as a food source by humans some decades ago also contributed to the frog's decline.
Bullfrogs may pose more of a threat than just predation: adult male red-leggeds have been observed attempting to mate with juvenile bullfrogs. Such interspecies dalliances may well interfere with successful reproduction.
The species was listed as Threatened by the U.S. Fish and Wildlife Service in 1996.
According to National Park Service (NPS) biologists, an estimated 100 or so adult red-legged frogs inhabit a short stretch of creek in the Simi Hills on the former Ahmanson Ranch, enough to allow transplanting of eggs into suitable creeks in the Santa Monica Mountains NRA without affecting the parent population. The problem is that red-legged frogs need trustworthy, year-round deep pools of water to thrive, and those are hard to come by in the Santa Monicas.
And what pools exist are often inhabited by introduced species such as crayfish, which are happy to chow down on frog eggs or young tadpoles.
Nevertheless, biologists from a consortium of agencies and groups including the California State Parks and NPS, USFWS, the U.S. Geological Survey's Western Ecological Research Center, and the Santa Monica Bay Restoration Commission will move red-legged eggs by the hundreds into likely spots in Ramirez and Solstice canyons. Delaney is urging the public not to mess with the mesh containers the team will be using to transfer the eggs into those streams, so as to give the frogs the best chance possible of putting down roots in a mountain range they once called home.
The egg planting effort is scheduled for Spring 2014. With any luck, some decades down the road we may be able to celebrate the Jumping Frogs of Calabasas.