For nearly five decades, scientists have sought to explain why amphibian numbers fell sharply at Brazil’s Boracéia Biological Station. A new study points to chytridiomycosis, a disease caused by the fungus Batrachochytrium dendrobatidis, as the likely cause of the declines recorded between 1979 and 1982.
Researchers from the Smithsonian’s National Zoo and Conservation Biology Institute and Pennsylvania State University tested more than 370 preserved amphibians, representing 17 species. The specimens came from museum collections gathered before and after the local die-offs.
None of the animals collected before 1979 showed evidence of chytrid. By contrast, more than half of those collected during the 1980s tested positive, indicating that the fungus spread through the area around the time populations were collapsing. The findings were published in Molecular Ecology.
The results varied by species. Frogs that suffered the steepest declines showed no detectable infection in the specimens, while species whose populations remained relatively stable often carried the fungus. The researchers suggest the most vulnerable frogs may have died before they could be collected, whereas more tolerant species could survive infection.
Surveys conducted at Boracéia between 2022 and 2024 found 12 of the 17 species represented in the historical collection. The other five were not detected, so their current status remains uncertain. Overall, the researchers report that most amphibian species at the site have recovered since the early 1980s, even though chytrid infections persist.
The study focuses on Boracéia and does not establish the cause of declines elsewhere in the Atlantic Forest. Researchers are now investigating DNA from museum specimens to identify factors that may have shaped species’ responses to the fungus. The findings also illustrate how archived specimens can help reconstruct disease outbreaks that were not understood when they occurred.
Sources: ScienceDaily.