Giving Tadpoles a Fighting Chance: A Novel Approach to Saving the Lemur Leaf Frog

When conservationists prepare to release endangered species back into the wild, they face a critical question: how do we give them the best chance at survival? For the lemur leaf frog (Agalychnis lemur), a species that has vanished from most known sites across its range, researchers are literally thinking outside the box.

Rather than releasing adult frogs directly into Panama’s forests, our research team took an innovative approach: introducing tadpoles bred in human care into large soft-release containers in the wild. Half of the containers were treated with antifungals to see if protecting animals at this critical stage can help frog survival.  This early intervention targets one of amphibians’ most devastating threats—the chytrid fungus Batrachochytrium dendrobatidis (Bd)—at a vulnerable life stage, potentially offering protection as the tadpoles metamorphose into adult frogs.

Agalychnis lemur breeds in slow-flowing swampy conditions. The species has experienced dramatic chytridiomycosis-related declines and has disappeared from most known sites, including a formerly occupied location in Altos de Campana National Park. While the species is breeding well in captivity and showing signs of recovery at a few sites in Costa Rica and Panama, these release trials could inform recovery efforts at many sites where this species has disappeared.

Previous research has shown promising results with fungicide treatments in artificial pond environments. Studies found that commonly used agricultural fungicides can reduce or eliminate Bd infections in susceptible tadpoles, with the fungicide degrading quickly and causing no significant harm to pond ecosystems or invertebrate communities.

This lemur leaf frog project brings together expertise from multiple institutions, including Gonçalo Rosa from IMIB Biodiversity Research Institute (CSIC) and ZSL, along with partners from the Panama Amphibian Rescue and Conservation Project, the Cheyenne Mountain Zoo, and Zoo New England. By creating artificial breeding points that can be safely treated with antifungal agents to reduce pathogen loads, the team is developing a replicable model that could help other endangered amphibian species facing similar threats.

The experiment is now underway, and researchers are monitoring whether this early antifungal protection helps the tadpoles survive disease once they complete metamorphosis. The results could inform future amphibian reintroduction programs worldwide, offering a practical tool in the fight against one of the most destructive wildlife diseases on the planet.


This research represents a collaborative effort to develop evidence-based conservation strategies for critically endangered amphibians in the face of emerging infectious diseases called the Tropical Amphibian Resilience Initiative funded by the Bezos Earth Fund and other donors to the Panama Amphibian Rescue and Conservation Project.  

Restoring Nature’s Soundscape

In the lush forests of Panama, a small rocket frog called Pratt’s rocket frog (Colostethus pratti) once filled the air with its distinctive calls. Then, a deadly fungal disease called chytridiomycosis swept through, decimating amphibian populations across Central America. In places like Altos de Campana National Park, where these frogs were once common, they vanished completely.

Pratt's rocket frog Colostethus pratti

During our acoustic monitoring research, we discovered that some C. pratti populations were bouncing back, even with the fungal pathogen still present. This suggested the frogs may have evolved resistance to the disease that nearly wiped them out. In Panama, we often find frogs that declined from the pathogen either recovering or persisting at low levels. But the fact that they declined to extinction in one national park while recovering elsewhere offered a unique opportunity: a human-assisted recovery of wild rocket frogs through translocation. In the United States, mountain yellow-legged frogs have recovered using this approach, and we hoped to replicate this success in Panama.

Twelve breeding pairs were collected from the recovering population at Bajo Bonito and brought to a quarantine facility, where they were tested for the fungus and treated preventatively. Male-female pairs then spent two weeks acclimating in mesh enclosures filled with leaf litter at the release site. Previous trials had shown that frogs released directly into new habitats dispersed rapidly and suffered higher mortality rates. This gentler approach gave them time to adjust before venturing into their new home.

The team is using acoustic monitoring technology—an array of automated recorders listening for the frogs’ loud, distinctive calls—to track the population over time. This cost-effective method will reveal whether the frogs survived and dispersed. For now, the forests of Altos de Campana have restored a missing voice to the soundscape—a small but significant victory in the fight to preserve the planet’s embattled amphibians. It’s still too early to evaluate whether the population will persist, but watch this space for updates!

Captive Breeding

Modern zoos and aquariums around the world specialize in captive breeding endangered species, they care for living collections of animals and help safeguard against their extinction. Our own project is a partnership between the Smithsonian’s National Zoo and Conservation Biology Institute, Cheyenne Mountain Zoo, Zoo New England and the Smithsonian Tropical Research Institute. This explainer video captures some of what zoos and aquariums around the world have been doing to breed endangered species.