Project overview: Continue research on one of Yosemite’s rarest mammals, which is at risk of extinction. Identify potential Yosemite habitat havens for the endangered population of Pacific fishers in the southern Sierra Nevada, where major wildfires and climate change are leading to severe habitat loss.

How your support helps: Pacific fishers — small, forest-dwelling mammals in the weasel family — face a major threat on the West Coast: habitat loss, driven largely by wildfires. The isolated population of fishers in the southern Sierra Nevada, which scientists estimate at fewer than 300 adults, was designated as federally endangered in May 2020. Past Conservancy-funded research in the 1990s and 2000s has detected as many as eight fishers in southern Yosemite.

As massive fires, such as the 2020 Creek Fire, destroy tens of thousands of acres of fisher habitat, scientists are racing to find out how the rare mammals are responding to the disruption — and how research and land management can help protect the species.

This year, with your support, researchers are using remote cameras, GPS collars and other tools to study how fishers move in and around recently burned areas in the southern Sierra Nevada, as well as how many of the mammals live in the northern part of their currently known range.

Through this project, scientists will gain a better understanding of how fire affects fishers, will be able identify potential “refuges” for the species in Yosemite, and will explore ways to help the southern Sierra Nevada fisher population expand its range farther north. They’ll also look for landscape corridors that link healthy forest areas, which could serve as natural byways for fishers to follow from one protected zone to the next. Ultimately, this research could help inform strategies for protecting fisher habitat that could be vital for the animals’ survival, especially as fires and drought threaten their southern range.

Project partners: Yosemite National Park, California Department of Fish & Wildlife, Integral Ecology Research Center, Sequoia & Kings Canyon National Parks, U.S. Fish & Wildlife Service, and U.S. Forest Service.

Sarah Stock

Wildlife Biologist, Yosemite National Park

Project Notes

“This study is urgently needed to fill critical knowledge gaps on fisher habitat use and connectivity in a landscape drastically altered by tree mortality and wildfire.”