Project overview: Uncover the unique role that otters play in Yosemite’s ecosystems — with a special focus on their predation impact on Sierra Nevada yellow-legged frogs — through camera trap monitors, DNA and scat collection, and scent detection dogs.

How your support helps: River otters were first seen in Yosemite National Park in 2014, possibly moving into the park as water levels declined elsewhere due to drought. With help from Conservancy donors, wildlife ecologists began studying these elusive and rarely seen otters via remote cameras and citizen science, but their impact on the park remains widely unknown. 

A central area of concern is their predation impact on threatened and endangered species in the park — namely, the Sierra Nevada yellow-legged frog. This frog species was once the most abundant amphibian in the Sierra Nevada high country, but experienced steep declines due to habitat loss, invasive diseases, and the introduction of fish into naturally fishless waters in Yosemite. By the early 2000s, the Sierra Nevada yellow-legged frog was on a clear trajectory towards extinction.  

Over the past decade, the Conservancy has funded efforts to restore high country lakes and reintroduce the once-common, now-endangered Sierra Nevada yellow-legged frog. Although this initiative has resulted in increased yellow-legged frog numbers in Yosemite, it is now unclear how the presence of river otters, a known predator of Sierra Nevada yellow-legged frogs, will affect the recent rebound of this frog population.  

The new River Otter Monitoring Project will analyze the parkwide impact of river otters on the success of Sierra Nevada yellow-legged frog reintroduction efforts, as well as the overall role that otters play in Yosemite’s ecosystems. This information is critical for park managers, as knowing where otters are establishing residence will guide locations to avoid for future frog reintroductions. 

This year: In 2026, the River Otter Project will conduct targeted river otter inventory and monitoring in Yosemite to benefit endangered Sierra Nevada Yellow-legged frog management initiatives. With your support, project scientists will develop an understanding of river otter impact in Yosemite via visual surveys, camera traps, environmental DNA, scent detection dogs, and scat collections to genetically identify individual otters.

Project partner: Yosemite National Park


Photo Credit: Richard Thornburgh