Long Beach Aquarium Saves Mountain Yellow‑Legged Frog
The Aquarium of the Pacific has successfully bred and released more than 1,000 mountain yellow‑legged frogs into California’s mountain streams, a species that was once on the brink of extinction. The program, a collaboration with the Los Angeles Zoo and federal agencies, aims to restore healthy pop…
By Felo News Desk · Published
In a quiet room at the Aquarium of the Pacific in Long Beach, a team of biologists is working to bring back a frog that once thrived in California’s mountain streams but has since teetered on the edge of extinction. The mountain yellow‑legged frog, named for the lemon‑streaked line on its hind legs, has seen its numbers plummet to just a few hundred individuals in the wild.
From Near Extinction to a Growing Population
When the species was listed under the federal Endangered Species Act in 2002, fewer than 100 adults remained in Southern California. A 2019 survey counted 188 frogs in the wild, a stark decline from the thousands that once inhabited the San Gabriel, San Bernardino and San Jacinto Mountains. The Aquarium of the Pacific’s program, now in its sixth year, has raised and released over 1,000 frogs, more than five times the number that survived the 2019 count.
The program began in 2021 after the 2020 Bobcat fire destroyed 95% of the frog’s remaining habitat. Rescue teams salvaged tadpoles from the fire‑impacted areas, and the aquarium began rearing them in controlled tanks that mimic the frogs’ natural environment. The tanks maintain a summer temperature of 60 °F and a winter temperature of 52 °F, with reduced UV exposure to simulate seasonal changes.
Collaborative Efforts and Release Strategy
Frogs are bred at the Los Angeles Zoo’s breeding program and then transferred to Long Beach as tadpoles. The aquarium staff raise them through metamorphosis, a process that can take one to two years, though some tadpoles remain in water for up to five years. Once they reach froglet stage, they are carefully separated by genetics and population of origin to preserve healthy lines.
In the latest release, 653 frogs were reintroduced into their native mountain streams by teams from the aquarium, the Los Angeles Zoo and the U.S. Geological Survey. A total of 1,032 frogs have been released to date. Some frogs are also sent to the Santa Ana Zoo each October to continue growing before reintroduction.
Facing the Invisible Threat: Chytrid Fungus
Beyond wildfire and habitat loss, the mountain yellow‑legged frog faces the microscopic chytrid fungus, which attacks amphibian skin and can cause cardiac arrest. Researchers hope that by breeding large numbers of frogs, they can identify genetic resistance to the fungus. Current studies test whether inoculation or introducing beneficial microbes to the frogs’ skin can help them fend off the pathogen.
Erin Lundy, a conservation biologist with the aquarium, says the program is “a strange kind of joy.” She has watched frogs she has cared for for years leap into the streams they were bred to repopulate, describing the moment as “a little bittersweet, like Christmas Day.”
What’s Next for the Frogs?
While the program has achieved a major milestone, the frogs remain vulnerable. Ongoing monitoring by the U.S. Fish and Wildlife Service, the U.S. Forest Service and the California Department of Fish and Wildlife is essential to track population health and ensure genetic diversity. The aquarium’s work continues to focus on mitigating chytrid fungus and expanding release sites as more frogs mature.
As climate change intensifies wildfire risk and water scarcity, the long‑term survival of the mountain yellow‑legged frog will depend on sustained conservation efforts and habitat restoration. The aquarium’s success offers hope that human intervention can reverse the decline of one of the world’s rarest vertebrates.
Key facts
- Over 1,000 frogs bred and released
- Program began after 2020 Bobcat fire
- Collaboration with LA Zoo, USGS, and federal agencies
- Chytrid fungus research underway
- Ongoing monitoring and habitat restoration needed
Why it matters
The mountain yellow‑legged frog is one of the world’s rarest vertebrates; its recovery showcases how targeted conservation can reverse species decline and protect fragile mountain ecosystems.
Frequently asked questions
What is the mountain yellow‑legged frog?
It is a small amphibian native to California’s mountain streams, known for a yellow streak on its hind legs.
Why was the species listed as endangered?
Its numbers fell to fewer than 100 adults by 2002 due to habitat loss, wildfire, pesticides, disease and predation by nonnative species.
How long does the rearing process take?
From tadpole to froglet can take 1–2 years, but some tadpoles may remain in water for up to five years.
What is chytrid fungus?
A microscopic pathogen that attacks amphibian skin, disrupting salt absorption and often leading to death.
What are the next steps for conservation?
Continued breeding, genetic studies, disease mitigation, and expanding release sites while monitoring populations.
Sources
- [1] latimes.com — originally reported as “A California frog is on the brink of extinction. Long Beach aquarium has a plan to save it”
