Scientists have uncovered a half-century-old mystery regarding the disappearance of frogs in Brazil

Scientists have uncovered the cause of the mysterious disappearance of frogs in Brazil's Atlantic Forest at the turn of the 1970s and 1980s, confirming an outbreak of the deadly chytrid fungus. This conclusion was reached by specialists from the Smithsonian Institution's Center for Conservation Genomics and Pennsylvania State University, whose work was published in the journal Molecular Ecology, as reported by ScienceDaily.

In search of the source of the catastrophe at the Boracéia biological station, researchers turned to the archival collections of the Smithsonian National Museum of Natural History. They tested over 370 specimens of 17 amphibian species collected by zoologist William Ronald Heyer. None of the specimens delivered before 1979 contained traces of the pathogen Batrachochytrium dendrobatidis, whereas among the findings from the 1980s, the proportion of infected individuals exceeded 50%.

The study also explained the paradox of why extinct species did not leave traces of infection in museum collections. According to the lead author of the study, Jack Boyette, the most vulnerable amphibians died too quickly to be collected by scientists, while less susceptible species survived, acting as asymptomatic carriers of the dangerous pathogen.

Expeditions by researchers and specialists from the University of São Paulo in 2022–2024 yielded promising results. Scientists recorded 12 out of 17 historical species, indicating the recovery of most populations. Although the microscopic fungus has persisted in the ecosystem, the frogs have acquired tolerance to the disease over the generations that have passed. Now, researchers are analyzing the DNA of old specimens to identify the genetic mechanisms of adaptation to infectious threats in the wild.