Yosemite celebrates return of California red-legged frog with release of 10,000th reared frog
Yosemite National Park marked a milestone in amphibian conservation with the symbolic release of the 10,000th reared California red-legged frog, “Twain”, after a decade of coordinated habitat restoration, invasive species removal and captive-rearing partnerships and research support.
- Milestone: The program released its 10,000th frog into Yosemite Valley — a frog nicknamed Twain.
- Partners: A multi-agency effort led by the National Park Service with federal, state, zoo and university partners.
- Methods: Invasive bullfrog removal, habitat restoration tied to the Merced River Plan, closure of open refuse sites and a San Francisco captive-rearing program that opened in 2016.
- Outcome: Multiple generations of California red-legged frogs now persist in Yosemite Valley despite droughts, severe winters and flooding.
Overview
Yosemite National Park and partners completed roughly a decade of coordinated work to restore the federally threatened California red-legged frog to Yosemite Valley. The program — which culminated in the symbolic release of the 10,000th reared frog on May 7 — uses a three-part strategy: remove threats, restore habitat and raise frogs in captivity for staged reintroduction.
Species background and historical decline
Species: The California red-legged frog is California’s state amphibian and the largest native frog in the western United States, typically 2 to 5 inches long, noted for a reddish belly and soft, short calls. These frogs occupy ponds, streams and wet meadows and act as indicators of wetland health.
Decades ago the frogs disappeared from Yosemite Valley. Park biologists attribute local extirpation to a combination of factors: the invasive American bullfrog, elevated raccoon populations fueled by open refuse sites into the 1970s, and habitat changes that reduced suitable breeding and sheltering sites.
Recovery strategy: removing threats and rebuilding habitat
Three-part approach:
- Threat removal: Years of targeted removal of invasive bullfrogs and closure of open refuse sites reduced predation and competition pressures.
- Habitat restoration: Work under the Merced River Plan restored wetlands, streambanks and river systems — efforts supported by grants managed in part by the California Department of Fish and Wildlife and voter-approved funding.
- Captive rearing: A dedicated rearing facility in San Francisco opened in 2016 as a partnership between the National Park Service and the San Francisco Zoo & Gardens, raising wild-collected eggs through vulnerable juvenile stages for staged release.
Captive-rearing methods and timeline
The San Francisco rearing facility opened in 2016. Staff collect eggs from remaining wild sources, rear them in tanks and managed ponds that mimic natural conditions, and release one- and two-year-old juveniles into restored sites. The phased rearing approach — developed with university researchers — aims to improve post-release survival and establish stable, multi-generation populations.
Partners and collaboration
This is a multi-agency effort with distinct roles:
- Leadership and coordination: National Park Service leads on-the-ground operations in Yosemite.
- Federal support: The U.S. Fish and Wildlife Service provides oversight and recovery support for the federally threatened species.
- State funding and grants: California Department of Fish and Wildlife helped secure and manage grants that enabled habitat projects.
- Rearing and zoo expertise: The San Francisco Zoo & Gardens runs the rearing facility.
- Nonprofit and research partners: Yosemite Conservancy and UC Santa Barbara contributed funding, research and technical expertise.
“Our partners have been essential to the recovery of the California red-legged frog. We appreciate the progress made over the past decade and remain committed to this collaborative effort.”
— Kim Turner, acting field supervisor, Sacramento Fish and Wildlife Office
“This milestone reflects years of focused work to restore a species that plays an important role in the park’s ecosystem… Today, multiple generations of frogs are established in Yosemite Valley.”
— Rob Grasso, aquatic ecologist, Yosemite National Park
“State grants helped make the habitat work possible.”
— Laura Patterson, amphibian and reptile conservation coordinator, California Department of Fish and Wildlife
On-the-ground progress and resilience
Every frog now living in Yosemite Valley traces back to the recovery program. Staff report the population has persisted through droughts, severe winters and large floods — evidence that restored habitat plus captive rearing are building ecological resilience. The symbolic release of the program’s 10,000th frog, nicknamed Twain, occurred near Yosemite Falls during a May 7 event marking the program’s 10-year anniversary.
Why this matters: ecological and indicator value
Ecological role: The California red-legged frog links insects and invertebrates to larger predators, helping keep wetland food webs balanced. Its presence signals healthy wetlands and functioning river systems. Restoration of this species supports broader ecological processes that benefit many plants and animals.
Yosemite’s recovery methods — from invasive species control to captive rearing and habitat engineering — provide a replicable model for recovering other threatened amphibians and wetland-dependent wildlife across California and beyond.
Implications for Los Angeles, California
Economic: Restored Sierra Nevada watersheds help regulate downstream water flow and contribute to long-term water quality and supply stability for urban users, including Los Angeles County.
Political & funding: The success underscores how voter-approved state grants and federal-state partnerships can yield measurable conservation outcomes — a point of reference for Los Angeles-area voters and officials when evaluating investments in watershed and habitat restoration.
Social & community: The frog’s comeback offers a tangible success story for schools, nature centers and advocacy groups in Los Angeles, strengthening public support for native-species programs and community-backed conservation.
Practical applications: Methods used in Yosemite — invasive species removal, improved waste management to limit predator attraction, targeted habitat restoration and captive-rearing partnerships — can be adapted for urban and suburban wetlands, parks and riparian corridors across Los Angeles.
Takeaway
The return of the California red-legged frog to Yosemite Valley — capped by the release of the 10,000th reared individual — demonstrates how long-term, collaborative conservation that removes threats, restores habitat and applies captive-rearing science can produce durable recovery outcomes.
