Research

Mountain yellow-legged frogs (Rana sierrae and Rana muscosa) were once abundant across the Sierra Nevada, but have disappeared from more than 90% of their historical range. This decline has resulted primarily from the introduction of non-native fish into thousands of naturally fishless lakes and streams, and the spread of the highly virulent amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). As a consequence, both species are now listed under the U.S. Endangered Species Act and are the focus of ongoing recovery efforts. 

In our early research on mountain yellow-legged frogs, we described the frog’s current distribution and population trend, primary causes of decline, and effect of fish removal on frog abundance. 

Currently, we are developing methods to recover mountain yellow-legged frogs in the face of chytridiomycosis, the disease caused by Bd. A primary focus is on frog translocation, in which frogs are collected from populations that are thriving despite ongoing Bd infection and moving them to nearby suitable sites that lack frogs. In partnership with the San Francisco and Oakland Zoos, we are also testing the effectiveness of frog reintroduction, in which early life stages (e.g., tadpoles) are collected from the wild, raised in captivity to adulthood , and then released back into the wild. The National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, and California Department of Fish and Wildlife all play important roles in this process. 

The Sierra Nevada contains thousands of lakes and ponds. Despite their importance to wildlife and people, until recently they were relatively little-studied. As a consequence, the species inhabiting these water bodies, structure of lake food webs, and impacts of fish introductions were all poorly understood. We’ve sought to remedy this using landscape-scale surveys, detailed observational studies, and whole-lake experiments. 

In the late 1990s and early 2000s, we surveyed more than 7,000 lakes and ponds in the central and southern Sierra Nevada. We used data collected in this survey effort to describe these habitats and their species composition, including native amphibians, benthic macroinvertebrates, and zooplankton, and non-native fish (click here for a species list compiled from samples and observations during this effort). This information and subsequent studies allowed description of the effect of non-native fish on lake fauna, the recovery of this fauna following fish removal, impact of changes to lake communities on the adjacent terrestrial ecosystem, and the effect of mountain yellow-legged frog extinctions on lake ecosystems. 

The findings from our research provide the foundation for lake recovery efforts being implemented in the Sierra Nevada by the National Park Service, U.S. Forest Service, and California Department of Fish and Wildlife. These efforts will ensure that sufficient numbers of lakes remain in their original fishless condition to support viable populations of native species.

In collaboration with the Environmental Data Initiative, we published the Sierra Lakes Inventory Project (SLIP) database, which is accessible to the public.

Underlying all of our research, we adhere to Open Science/Open Research principles and best practices. We strive to make our research reproducible and to make our results available to the public. You can explore our analyses, reports, and computer code on our public GitHub repository, and our protocols and our peer-reviewed scientific publications on this site.