Early explorers once described scores of frogs sunning themselves along the edges of Yosemite National Park lakes. But fish stocking and the arrival of a deadly fungus pushed the Sierra Nevada yellow-legged frog to the brink of extinction. Today, scientists have mounted an epic comeback for these integral amphibians.
At one time the rare Sierra Nevada yellow-legged frog (Rana sierrae) was the most abundant amphibian in the high mountain lakes of the Sierra Nevada. Populations have since declined approximately 95% in the Sierra Nevada, including in Yosemite, according to the National Park Service.
Dwindling numbers
When the Yosemite area was first discovered by California miners, they were impressed with the natural beauty, but lacked food resources in the remote areas. The solution was stocking the impressive mountain lakes with an abundance of fish.
The non-native trout ate many of the Sierra Nevada yellow-legged tadpoles, slimming down the frog populations. Then the dreaded amphibian chytrid fungus arrived in the park, decimating frog populations even in fish-free lakes.
“It was a double whammy that almost wiped out the species,” Roland Knapp, a research biologist at the University of California, Santa Barbara, told USA Today. Knapp has been part of the research team studying the frogs for the past 30 years.
An epic recovery
Knapp and a team of biologists scoured the lakes for any remaining frogs, and remarkably found some of the frogs had evolved a resistance to chytrid fungus.
The biology team reintroduced the fungus-resistant frogs to 12 lakes in Yosemite and have helped lead the effort in removing and reducing non-native fish populations in the lakes.
Since implementing these efforts, frog populations have skyrocketed. While they are still listed as an endangered species, there is hope for their continued recovery in the park.
“The lakes are alive again, completely transformed,” said Knapp.
The research included scientists from the University of Tennessee, Colorado University and Yosemite National Park. Their findings were published in the journal Nature Communications.
Their research has implications for many amphibian species facing extinction, driven in part by the emergence of the lethal fungus.
By reintroducing the fungus-resistant frogs into new areas, the scientists are not only saving the Sierra Nevada yellow-legged frog but also helping protect the ecosystem of which they are a vital part.