Scientists Use Climate Data to Map, Predict Amphibian Chytrid Disease

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.