Yosemite marks milestone as 10,000th California red‑legged frog returns after 50‑year absence
Yosemite National Park marks a conservation milestone as the 10,000th California red‑legged frog — nicknamed “Twain” — was released after a 50‑year absence, following a decade of bullfrog removal, habitat restoration and captive rearing through collaborative efforts.
Key takeaways
- Symbolic release: The program’s 10,000th frog, “Twain,” was released in Yosemite Valley near Yosemite Falls.
- Collaborative recovery: Led by National Park Service, Yosemite National Park news, U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, Yosemite Conservancy and San Francisco Zoo & Gardens.
- Recovery tools: Invasive bullfrog removal, Merced River Plan habitat work, and a San Francisco rearing facility launched in 2016.
- Evidence of success: Multiple generations and natural breeding observed — program released roughly 10,000 animals to date.
Yosemite milestone and recovery overview
After roughly 50 years without the species in Yosemite Valley, park and partner staff celebrated a turning point: the symbolic release of the program’s 10,000th California red‑legged frog, nicknamed “Twain.” The achievement caps a decade of coordinated work that combined threat removal, habitat rebuilding and captive rearing to reestablish wild, breeding populations.
How the species disappeared — and why its return matters
The California red‑legged frog, the largest native frog in the western U.S., was extirpated from Yosemite Valley due to introduced American bullfrogs, increased raccoon predation (fueled by open refuse sites into the 1970s), wetland loss and altered river systems. Park ecologists say restoring the frog helps rebuild pond and stream food webs and is an indicator of broader ecosystem recovery.
“This milestone reflects years of focused work to restore a species that plays an important role in the park’s ecosystem,” said Rob Grasso, aquatic ecologist at Yosemite National Park.
A decade of coordinated work: what partners did
The recovery accelerated after a rearing facility opened in San Francisco in 2016 through a partnership between the National Park Service and the San Francisco Zoological Society. At that facility juveniles are reared from wild‑collected eggs to one‑ and two‑year‑old frogs under controlled conditions before release.
On the landscape, crews conducted sustained campaigns to remove invasive bullfrogs, while Merced River Plan projects restored wetlands, rebuilt streambanks and reconnected ponds — creating safer habitat for released juveniles to survive and breed.
Numbers and evidence of success
Program teams have released thousands of eggs, tadpoles and juveniles; the program reached a symbolic milestone with the 10,000th frog. Field monitoring reports multiple generations in the valley and observed natural breeding among released animals — strong evidence the population is establishing itself rather than relying on a single cohort.
Resilience: Released frogs have persisted through drought, severe winters and flooding over the recovery decade, according to program partners.
Funding, grants and community support
The California Department of Fish and Wildlife helped secure and administer grants — including voter‑approved conservation funds — that financed habitat restoration. Federal grants from USFWS, private donors through Yosemite Conservancy, and other sources funded on‑the‑ground work and long‑term monitoring.
Quote: “We appreciate the progress made over the past decade and remain committed to this collaborative effort,” said Kim Turner, acting field supervisor for the Sacramento Fish and Wildlife Office.
How the rearing facility works
Staff collect eggs from wild sources and rear them through vulnerable early stages in controlled settings that reduce disease and predation risk. Juveniles are released at one or two years old — large enough to improve survival yet able to adapt to natural conditions. On average the program releases roughly 830 juveniles annually and rears about 600 eggs per year for future releases.
Genetic monitoring ensures healthy diversity and helps track survival, breeding and spread after release.
Lessons learned and a model for other places
Yosemite’s success combined threat removal, habitat restoration and captive rearing with long‑term monitoring. That sequence — especially targeted invasive predator removal and thoughtful habitat rebuilding — is now informing other projects across California, including work in Napa County that has produced new breeding populations.
Yosemite amphibian restoration: science meets long‑term stewardship
The Merced River Plan’s wetland and floodplain reconnections provided ponds and slow water needed for egg laying and tadpole growth. Continued bullfrog removal and reduced raccoon access at sensitive sites complement habitat work. Monitoring teams tag animals, survey ponds and feed data into adaptive management to respond to droughts and floods.
Implications for the Inland Empire
Economic: The high‑profile recovery and release events can boost ecotourism interest and support businesses serving outdoor visitors.
Political: The partnership and funding model — including voter‑approved funds administered by CDFW — provides a template for local conservation finance and policy in the Inland Empire.
Social & practical: Community outreach, volunteer programs and head‑start rearing approaches offer replicable tools for regional agencies managing floodplains, ponds and urban streams.
