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Study Brings Hope For California's Yellow-Legged Frog

Roland Knapp, UCSB Sierra Nevada Aquatic Research Laboratory
Sierra Nevada yellow-legged frog (Rana sierrae)

Chytridiomycosis fungus causes disease and death in amphibian populations around the world. In Yosemite, the fungus has wreaked havoc since it appeared in the 1960s.

UC Santa Barbara biologist Roland Knapp led a team of scientists from a number of institutions who analyzed Yosemite's frog population data over a 20-year period. He says they were surprised to find the number of yellow-legged frogs had increased sevenfold since 1991.

Knapp says the findings suggest the frogs adapted over time.

"Frogs that have been exposed to that pathogen now for twenty or more years in Yosemite are less susceptible to that pathogen and the disease it causes than frogs that are naive to that pathogen," explains Knapp.

The study offers a hopeful sign for the yellow-legged frog's recovery, but Knapp cautions that more research is needed to determine if other amphibian species across the world could adapt to harmful stressors in this way.

This one little species is part of a bigger story. Because the native California species was so abundant historically, Knapp says it likely played a big role in the aquatic food web as both predator and prey.

In other words, when the yellow-legged frog disappeared so did its predator the garter snake. 

"By keeping these frogs in these ecosystems over the long-term and doing what we can to allow them to recover," says Knapp "we're protecting not just frogs, we're protecting a whole system that's within a national park.”

The chytrid fungus has caused at least 200 species of frogs and salamanders to become extinct in the last thirty years.

This story was produced by Capital Public Radio.