# Uncovering the Fungal Cause of Brazil's Historic Amphibian Declines Museum specimens reveal how a deadly pathogen triggered mass frog population collapses. - **Source:** [Latest Science News -- ScienceDaily](https://brifing.si/source/0eef8637-6c5b-4e79-8f5b-6c9c6b36cf16) - **Published:** 2026-11-03 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/e1d2bc40-2b0e-400d-9879-9bffbcee1129 ## Decades of Unexplained Losses For nearly fifty years, the sudden disappearance of frogs in Brazil's Atlantic Forest remained a scientific mystery. While researchers documented severe population declines starting in the 1970s, the underlying cause stayed elusive. Recent investigations now point to chytridiomycosis, a deadly fungal disease, as the primary driver behind these historical wildlife die-offs. ## The Role of Chytrid Fungus The pathogen Batrachochytrium dendrobatidis, commonly known as chytrid, likely originated in Asia before spreading globally during the 1970s and 1980s. Although the fungus was not formally identified until 1999, it had already devastated hundreds of amphibian species worldwide. This delayed discovery turned many regional population collapses into enduring wildlife epidemiology cold cases. ## Leveraging Historical Museum Collections Researchers utilized preserved frog specimens from the Smithsonian's National Museum of Natural History to reconstruct the outbreak. By analyzing over 370 samples collected by William Ronald Heyer at Boracéia, the team compared infection rates before and after the 1979 decline. This provided a unique timeline of the pathogen's arrival and rapid spread. ## Surprising Patterns in Infection Testing revealed that no specimens collected before 1979 carried the fungus, while over half tested positive during the 1980s. Interestingly, species that suffered the most severe declines showed no detectable infection, likely because they died too quickly to be collected. Conversely, stable species often carried the fungus, suggesting a natural tolerance. ## Distinguishing Infection from Mortality The findings highlight a critical distinction between carrying a pathogen and suffering catastrophic mortality. Some species appear to have developed a natural ability to tolerate the fungus, allowing them to survive despite persistent exposure. This resilience explains why certain populations rebounded while others faced near-extinction during the initial, rapid invasion of the pathogen. ## Modern Value of Archives Michael Campana notes that museum collections hold biological evidence that early collectors could never have anticipated. Modern genomic testing allows scientists to revisit these archives to identify pathogens that went unnoticed for decades. This capability is essential for reconstructing disease outbreaks and understanding the long-term impacts of environmental threats on biodiversity. ## Recovery and Future Threats Surveys conducted between 2022 and 2024 at Boracéia indicate that most surviving amphibian species have recovered since the 1980s. While the fungus remains present, increased tolerance across generations likely supports this rebound. Researchers are now using these insights to anticipate threats from other pathogens, such as B. salamandrivorans, which currently endangers salamander populations. ## Advancing Conservation Genomic Research Ongoing research now focuses on DNA recovered from museum specimens to identify genetic mechanisms behind species-specific responses to chytrid. By combining these findings with ancient environmental DNA analysis, scientists aim to create a clearer history of fungal emergence. These efforts provide a roadmap for protecting vulnerable species against future global fungal epidemics. ## Sources covering this story - https://www.sciencedaily.com/releases/2026/11/261102202838.htm — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._