Frogs collected in Brazil’s Atlantic Forest in the 1970s carried no sign of the chytrid fungus, while more than half of those collected in the 1980s tested positive. That contrast, drawn from more than 370 preserved museum specimens, points to the fungus as the likely cause of amphibian die-offs at one forest station between 1979 and 1982. The finding closes in on a mystery that has gone unsolved for nearly half a century.
Free daily tech newsletter: TLDR is the free daily newsletter with links and TLDRs of the most interesting stories in startups, tech and programming.
We may earn a commission if you sign up.
Jack Boyette, a graduate fellow at the Smithsonian’s National Zoo and Conservation Biology Institute and a doctoral candidate at Pennsylvania State University, led the study. After almost 50 years, he said, researchers still lack confidence about what caused many historical amphibian die-offs.
Heyer’s specimens from the Boracéia Biological Station
The evidence sits in jars. William Ronald Heyer, a former curator of amphibians and reptiles at the Smithsonian’s National Museum of Natural History, collected frogs at the Boracéia Biological Station across five field campaigns, two in the 1970s and three in the 1980s. According to the Smithsonian’s National Zoo announcement, the team tested more than 370 of those specimens, representing 17 species, for the fungus and tracked how common infection was over time.
The timing lines up with the losses. Amphibian populations at Boracéia collapsed between 1979 and 1982, and specimens gathered before 1979 showed no chytrid infection at all. In the 1980s collections, more than half of the frogs tested positive. A sudden arrival of the pathogen, rather than a long-standing background infection, fits that sequence, and the researchers conclude that the results most directly implicate the chytrid fungus.
The study appeared on October 14 in Molecular Ecology, under the identifier DOI 10.1111/mec.70573. The University of São Paulo also contributed to the field sampling that complements the museum work, which gave the team a modern baseline for comparison. Returning to Boracéia six times between 2022 and 2024 let researchers ask a question that museum shelves alone cannot answer, namely which of the frogs Heyer once collected still live in the forest today. That pairing of old specimens with new field surveys is what turns a collection of jars into a record of disease, loss and recovery across more than four decades.
Tolerant frogs, vanished frogs and 12 of 17 species
The pattern across species is stranger than a simple die-off narrative. The species that declined the most had no detectable infections in the museum samples, while species that never declined were heavily infected. The researchers suggest that reflects natural differences in disease tolerance. Boyette’s explanation is that the most-declining species may have been so susceptible that infected frogs died before anyone could collect them, leaving only healthy-looking specimens on the shelf.
That logic echoes earlier Brazilian work. A 2017 study of more than 30,000 museum-preserved tadpoles collected between 1930 and 2015, posted as a supplementary collection on figshare, found more infected tadpoles during 1979 to 1987, the peak of declines, and clusters of infection overlapping with most recorded declines in the Atlantic Forest. Reporting in Pesquisa FAPESP noted that tadpoles served as useful evidence because infected adults usually died quickly and rarely reached museum collections.
The Boracéia result adds a second chapter: partial recovery. The team returned to the station six times between 2022 and 2024 and, of the 17 species in Heyer’s collection, found 12 on site. The fate of the other five remains uncertain. Most amphibian species there appear to have recovered since the early 1980s, even though the fungus still infects frogs at the station, and the researchers suggest tolerance may have evolved among the species that once declined.
One site, not the whole Atlantic Forest
The authors are careful about scope. The study covers a single site, so its conclusions cannot be extended to the wider Atlantic Forest, where other causes may have mattered elsewhere. The fungus itself was formally described only in 1999, which means nobody was testing for it when the frogs of Boracéia vanished. The disease chytridiomycosis has since been tied to amphibian declines on several continents.
Michael Campana, a genomicist at the National Zoo and Conservation Biology Institute, said the collectors who filled these shelves could not have anticipated how important their collections would become for modern conservation challenges. The team is now extracting DNA from museum samples to study the genomic mechanisms behind responses to chytrid, and using ancient environmental DNA to fill gaps in the historical record.
The announcement also notes a newer threat, the fungus Batrachochytrium salamandrivorans, which endangers European salamanders and may pose a risk to North American salamanders. Lessons from the old Brazilian die-off, including how quickly a susceptible species can disappear and how tolerance can emerge afterward, may help conservationists judge which species to watch before the next outbreak, rather than decades after it. For a pathogen that was not formally described until 1999, the preserved frogs of the 1970s and 1980s are often the only surviving witnesses, which is why the authors treat museum collections as active tools for conservation rather than archives of the past.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
More from Morning Overview
- Lake Powell sank to a record 3,517 feet, nearing the level that stops Glen Canyon Dam’s turbines
- Seven of Earth’s nine planetary boundaries are breached, and all seven are worsening
- The NSA says three phone features should be off whenever you aren’t using them
- Hurricane Hunter radar shows four warning signs that a tropical cyclone is about to strengthen, a University of Miami study found
