What makes a good home for a crowned tree frog Triprion spinosus? That’s the question Smithsonian scientists set out to answer as they work to reintroduce captive-bred frogs back into their natural habitat.
In the wild, male crowned tree frogs are picky about real estate. They search for water-filled tree cavities where they call out to potential mates. If a female approves of his choice, she’ll lay her eggs in that carefully selected pool.
But when releasing frogs bred under human care, researchers wanted to stack the odds in their favor. The solution? Build artificial tree holes from different materials and let the frogs choose their favorites.
Newly released frogs began exploring right away, and we were able to track their movements for the first few weeks using a radiotransmitter. Before long, their calls echoed through the forest as they settled into their new homes, we will continue monitoring the artificial tree holes to see if we get any eggs laid in these structures and continue to explore other tree hole designs.
This research is part of the Tropical Amphibian Research Initiative, supported by the Bezos Earth Fund and conducted through collaboration among the Panama Amphibian Rescue and Conservation Project.
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.
Meet Jorge Guerrel manager of the Panama Amphibian Rescue and Conservation Center and Dr. Gina DellaTogna STRI research associate and executive director of the Amphibian Survival Alliance who has been leading assisted reproduction research efforts around the world.
The chytrid fungus disease is responsible for global amphibian population declines, such as the endangered limosa harlequin frog shown above. (Brian Gratwicke/Smithsonian’s National Zoo and Conservation Biology Institute)
Researchers may have a new tool in the fight to protect neotropical frogs from extinction, thanks to climate data. In a recently published study in the journal Diversity and Distributions, researchers from the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) and the Smithsonian Tropical Research Institute (STRI) created a high-resolution map of Panama showing how a deadly amphibian disease moved across Panama over a 13-year period. But the data also provides insight into where the disease is the most dangerous and shows regions that may be havens for reintroduced, captive-bred frogs.
Since its first scientific description in 2000, Batrachochytrium dendrobatidis (Bd), a fungus that causes the deadly amphibian chytrid disease, has devastated amphibian populations in Central and South America. Believed to have originated in Asia, chytrid has since spread to many parts of the world, and the disease is responsible for wiping out nine frog species in Panama alone.
Like other fungi, chytrid requires a cool, wet environment to thrive. In chytrid-friendly conditions, disease outbreaks can decimate frog populations. But scientists have found that the fungus cannot thrive when the temperature is too high or the air is too dry. While the disease has spread throughout mainland Panama, the team wondered if the climate parameters might create an opportunity to find pockets where chytrid was less likely to kill.
By pairing satellite data with 13 years’ worth of atmospheric modeling, researchers created an ultra-high-resolution, daily temperature and humidity map for the nation. They paired this with a second dataset of over 4,900 disease samples taken from 314 sites across Panama. The second dataset tracked the amount of fungus present on each frog, known as the fungal load, over 13 years. When overlaid, the two data sets provided a clear picture of when and where the chytrid disease was the most intense. Higher elevations consistently remained more hospitable to the fungus, but rainy seasons brought chytrid-friendly conditions to the lowlands and led to waves of outbreaks.
“By compiling the hard-earned data from many amphibian researchers, we have been able to draw an unprecedented, detailed picture of the intensity of Bd in Panama through time and space,” said Carrie Lewis, doctoral student at George Mason University’s Department of Geography and Geoinformation Science, who led the study. “My hope is that we can use this detailed information to inform conservation actions in a more refined way.”
Although chytrid disease has devastated amphibian populations, the presence of the chytrid fungus alone is not a death sentence. Recognizing this, the research team built three models: one showing fungal presence; a second at “medium intensity,” which researchers consider an indicator of a serious infection; and a third at “high intensity,” which researchers associated with significant disease outbreaks. Researchers found that by examining the weather conditions 15 days prior to sampling, they could predict the presence and intensity of the chytrid fungus.
By mapping out the path and intensity of chytrid, it became clear that the disease thrives in mountainous regions, which tend to remain cooler and more humid than lowland areas. With this knowledge, researchers may be able to identify climatic refuges—areas less suitable for the chytrid disease where frogs may have a fighting chance against the fungus.
“The ability to identify places where frogs might be able to survive chytrid is critical for two reasons,” said Brian Gratwicke, NZCBI biologist and senior author of the study. “One, it allows us to look for frogs in those areas who might have developed resistance to the fungus. Two, those same areas might be sites where we can return captive-bred frogs into the wild. Both aspects could be significant turning points in the fight against the chytrid disease.”
Since 2009, the Panama Amphibian Rescue and Conservation Project based in Gamboa, Panama, has bred 12 species of frogs, all of which are facing extinction. After years of successful breeding, there are now enough animals to begin rewilding efforts. As researchers work toward reintroduction trials for imperiled Panamanian species, these prediction models will be crucial to determining when and where trials should take place.
This collaboration between 18 coauthors was partially supported with funding from the National Science Foundation, the German Science Foundation and the Bezos Earth Fund through the Tropical Amphibian Research Initiative.
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.
