UNIVERSITY PARK, Pa. -- What doesn't kill them makes them stronger. That old adage appears to hold true for the endangered Sierra Nevada yellow-legged frog, and Penn State researchers hope it is relevant for disappearing amphibians in the eastern United States, too.
A new study published today (Oct. 3) in an early online edition of the Proceedings of the National Academy of Sciences shows that after decades of decline – and despite continued exposure to stressors such as non-native fish, disease and pesticides – the frog's abundance across Yosemite National Park has increased seven-fold, and at an annual rate of 11 percent, over a 20-year study period.
Those increases, occurring over a large landscape and across hundreds of populations, provide a rare example of amphibian recovery at an ecologically relevant scale -- and fly in the face of the continuing steep decline of frog and salamander populations worldwide.
The yellow-legged frog's comeback out West seems to show that amphibians have the capacity to develop resistance to disease and tolerance for contaminants and suggests that they can survive in the East and around the world. At least that's the hope of David Miller, assistant professor of wildlife population ecology in Penn State's College of Agricultural Sciences, who is a member of the research team.
That team, led by University of California Santa Barbara biologist Roland Knapp, also included scientists from the U.S. Geological Survey, San Francisco State University and the University of California Berkeley. The study analyzed more than 7,000 frog surveys conducted at hundreds of sites over more than 20 years. Knapp, based at the Sierra Nevada Aquatic Research Laboratory in Mammoth Lakes, has been studying the yellow-legged frog in Yosemite for 15 years.
Miller's contribution to the research involved organizing, analyzing and interpreting the massive amount of data collected by the study. He noted that the findings indicate that given sufficient time and the availability of intact habitat, amphibians can recover despite the human-caused challenges they face.