Museum specimens have given researchers a likely explanation for severe amphibian declines between 1979 and 1982 at BoracĂ©ia Biological Station in Brazilâs Atlantic Forest: chytrid fungus was spreading through the area at about the same time. Smithsonian researchers and colleagues at Pennsylvania State University reported the findings in a Smithsonian account published by ScienceDaily. The evidence implicates the fungus at this location; it does not establish that it alone caused the declines.
The team tested more than 370 preserved amphibians representing 17 species, using collections that included specimens gathered by former Smithsonian curator William Ronald Heyer. None of the specimens collected before 1979 showed evidence of chytrid infection. More than half of those collected during the 1980s tested positive. Those results describe the tested specimens, not every amphibian at Boracéia.
Chytridiomycosis, often called chytrid, is a disease caused by the fungus Batrachochytrium dendrobatidis. Jack Boyette, who led the research, said environmental factors could also have played a role, but that the findings âmost directly implicate the chytrid fungus.â The pathogenâs spread coincided with the unexplained disappearances, he said.
There is a complication: the species with the worst declines showed no detectable infection in the preserved specimens, while relatively stable species frequently carried the fungus. Boyette proposed that infected frogs in more susceptible species may have died before Heyer could collect them. That remains a hypothesis, not a record of infected deaths among the hardest-hit species.
During six visits between 2022 and 2024, researchers found 12 of the 17 species represented in the historical collection. They did not find the other five. The surveys indicate that most species at Boracéia have recovered since the early-1980s declines, even though chytrid infections persist. The researchers suggest some frogs may have developed greater tolerance, but are still investigating why species responded differently. Their findings are specific to Boracéia and cannot automatically explain amphibian disappearances elsewhere in the Atlantic Forest.
