Yosemite marks milestone as 10,000 California red‑legged frogs returned after decade of restoration
Yosemite National Park marked a decade of restoration on May 7, 2026, as partners celebrated reintroducing over 10,000 California red‑legged frogs to Yosemite Valley, with evidence of multiple breeding generations and restored wetland habitats and resilience.
- Milestone release: The program’s symbolic 10,000th frog, nicknamed “Twain”, was released near Yosemite Falls on May 7, 2026.
- Threats addressed: Invasive American bullfrogs, elevated raccoon predation from historic open refuse, and altered river channels were targeted for removal and restoration.
- Strategy: Roughly 10,000 individuals were released since 2016 (eggs, tadpoles, juveniles, some adults), favoring 1–2‑year juveniles raised at a San Francisco rearing facility for higher survival.
- Partners & funding: Multi‑agency effort led by NPS with U.S. Fish & Wildlife Service, California Department of Fish and Wildlife, Yosemite Conservancy, San Francisco Zoo & Gardens and others, supported in part by voter‑approved state grants.
How the Yosemite frog recovery began
The California red‑legged frog (Rana draytonii), California’s state amphibian and a federally threatened species, had disappeared from Yosemite Valley by the 1970s. Invasive American bullfrogs — introduced decades earlier — preyed on and outcompeted the native frogs. Elevated raccoon numbers, bolstered for years by open refuse sites in use until the 1970s, consumed eggs and tadpoles. Altered river channels and damaged wetlands further reduced safe breeding habitat.
After surveys showed no self‑sustaining population remained, park staff and partners launched a reintroduction program in 2016. As Rob Grasso, aquatic ecologist at Yosemite National Park, said:
“After invasive bullfrogs eliminated red‑legged frogs from the area decades ago, we removed those threats and created conditions for recovery. Today, multiple generations of frogs are established in Yosemite Valley.”
Removing invasive threats and restoring habitat
A core tactic was sustained removal of bullfrogs from ponds and waterways. Park crews spent years trapping and removing bullfrogs and treating waterbodies where needed. Concurrently, the Merced River Plan guided restoration of wetlands, streambanks and floodplain habitats essential for breeding and juvenile survival. State grants helped finance on‑the‑ground projects that improved habitat connectivity and refugia for early life stages.
“The California Department of Fish and Wildlife is proud to have assisted the recovery of California’s official state amphibian in Yosemite,” said Laura Patterson, amphibian and reptile conservation coordinator for CDFW, noting that voter‑approved funds administered by the Department supported necessary habitat projects.
How frogs are raised and released
Partners collect wild eggs and rear frogs in a controlled setting to boost survival odds. A dedicated rearing facility in San Francisco, built through a partnership between the National Park Service and the San Francisco Zoological Society in 2016, raises frogs from eggs to one‑ and two‑year‑old juveniles. These juveniles have higher survival rates than eggs or small tadpoles released directly into the wild.
San Francisco Zoo staff and partners transport juveniles to Yosemite for staged releases. Rochelle Stiles of the zoo’s conservation team has said every frog now in the valley traces its lineage to that captive‑rearing effort. During the May 7 ceremony, zoo‑reared frogs were released into restored ponds, including the symbolic 10,000th frog, nicknamed “Twain”.
Evidence of success: breeding, resilience, and growing numbers
Signs of breeding returned early. By spring 2019, park biologists documented egg masses in ponds and meadows — a clear indicator that reintroduced frogs were reproducing. Monitoring since has found multiple generations in Yosemite Valley.
Program partners report the reintroduced population endured droughts, severe winters and floods, demonstrating the resilience of restored habitats and the frogs. In early 2026, partners observed roughly 20 egg batches since March, representing tens of thousands of tadpoles. Long‑term monitoring supports the conclusion that a self‑sustaining population is forming.
Scale and methods: numbers and strategy
Across the decade, managers released about 10,000 frogs in various life stages: eggs, tadpoles, juveniles and some adults. The favored approach prioritized releasing one‑ and two‑year‑old juveniles from the San Francisco facility because these age classes survive at higher rates once released. That captive‑rearing strategy, combined with invasive species removal and habitat restoration, moved the project from repeated releases to evidence of wild reproduction.
Partners and funding
This recovery represents a multi‑agency collaboration: the National Park Service led monitoring and habitat work; the U.S. Fish & Wildlife Service provided technical and regulatory support; the California Department of Fish and Wildlife administered grants from voter‑approved funds for habitat restoration; Yosemite Conservancy contributed funding and outreach; and the San Francisco Zoo raised frogs for release. Youth education groups like NatureBridge provided hands‑on experiences for young visitors during release events.
Acting Sacramento field supervisor Kim Turner (USFWS) praised the collaborative effort and pledged continued commitment to the recovery work.
May 7 event: a symbolic return
Park officials and partners gathered near Yosemite Falls on May 7, 2026, for remarks and release of several zoo‑reared frogs. The release of “Twain”, the 10,000th individual, served as a symbol of the decade‑long effort. Speakers emphasized both the numerical milestone and the science and teamwork behind it — from trapping bullfrogs to rebuilding wetlands.
Why the California red‑legged frog matters
The red‑legged frog plays a central role in riparian food webs: they consume aquatic insects and serve as prey for birds and snakes, helping balance stream and pond ecosystems. Restoring their populations supports other native species and improves water‑system health — benefits that extend downstream to people, farms and water districts.
Implications for the United States
- Economic & local stewardship: The Yosemite recovery demonstrates how federal, state and local partners can restore native species with targeted grants and community partnerships rather than large, permanent federal programs.
- Agriculture & water systems: Restored wetlands and riparian areas improve water retention and reduce erosion, contributing to more stable flows and better water quality for downstream users.
- Invasive species control: The years‑long effort required to remove bullfrogs highlights the cost of entrenched invasions and the value of early detection and rapid response programs.
- Community engagement & replicability: Hands‑on release events and youth programs built local support; the project offers a blueprint—remove invasive predators, restore habitat, use captive rearing, and coordinate multi‑partner funding—that can be applied elsewhere.
Sources and further reading
- California Department of Fish and Wildlife news and releases
- National Park Service, Yosemite National Park
- Yosemite Conservancy
- San Francisco Zoo & Gardens
- U.S. Fish & Wildlife Service
- High Country News
- ABC30 (KFSN) Fresno
Reporting based on agency releases and public reporting from NPS, CDFW, Yosemite Conservancy, San Francisco Zoo & Gardens, U.S. Fish & Wildlife Service, High Country News and regional media. Specific remarks cited from CDFW and NPS statements issued May 7, 2026.
