The researchers took previously developed models that showed where the disease occurred and when it was most severe, and combined them into new suitability maps. These maps pinpoint locations where the climate keeps infections at low intensity year-round, giving reintroduced frogs a realistic chance of survival.

"By mapping climatic refuges, we finally have a tool to rank potential release sites, allowing us to select places where the released animals have the best chance of survival," Gratwicke said.

What did the surviving toads reveal?

The team then tested their maps against reality: where do harlequin toads actually persist in Panama today?

The answer was striking. Most species survive only at sites where more than 80% of the seasons were unsuitable for medium- and high-intensity infections. In other words, the toads cling to existence almost exclusively in the climatic pockets the models predict should be safest.

One exception stood out. The variable harlequin toad (Atelopus varius) was found even at sites the models classified as suitable for the disease. The scientists say this fits with existing evidence that this particular species may have evolved resistance to chytrid — a rare piece of good news in amphibian conservation.

The maps do more than identify reintroduction sites. They also suggest where wild Atelopus populations might still be hanging on, undetected, in remote corners of their former range.

"Our ability to identify climate refugia is critical if we hope to locate populations that might have disappeared from most places in their former range," said Carrie Lewis, a doctoral candidate at George Mason University and lead author of the publication. "These persisting populations could provide a source of genes to bolster populations under human care and provide opportunities to augment wild populations."

Can climate change help — or hurt?

The number of potential refuges is currently limited, but the models also look forward. They forecast areas that are suitable for chytrid today but may become unsuitable in the coming years as the climate shifts — effectively creating new refugia over time.

That silver lining comes with a caveat the researchers are careful to stress. A shifting climate could also harm frogs adapted to cooler mountainous habitats. A site that becomes too hot for chytrid might, in some cases, become too hot for the frogs themselves.

The findings also remain preliminary in an important sense: they are model-based predictions, not yet confirmed by long-term field results. The climate refugia hypothesis still needs experimental validation through actual releases.

What happens next?

That testing has already begun. Guided by the climate refugia maps and Atelopus habitat-suitability models, the team has started surveying candidate sites for habitat quality and preparing potential release trials.

"These tools will allow us to experimentally test the climate refugia hypothesis through future release trials," said Roberto Ibáñez, a STRI staff scientist and co-author of the study.

For a genus that has lost so much ground since the 1970s, the work offers a cautious but concrete path forward: match the animal to the climate, rather than hoping captive-bred frogs can outlast a fungus that never leaves.