Fungal evidence sheds light on historic frog declines in Brazil

What you need to know

• The researchers tested more than 370 museum specimens representing 17 species, alongside contemporary frogs sampled at Boracéia between 2022 and 2024. This allowed them to compare evidence of infection across historical and recent samples. 12
• No chytrid fungus was detected in specimens collected before 1979. Among frogs sampled during the 1980s, after the declines, 58.8% tested positive. The authors interpret the timing as evidence that the fungus’s spread likely contributed to the local declines. 1
• The study suggests that infection tolerance may have become more widespread and could help explain local recovery. However, this remains an interpretation: infection rates in field samples alone cannot show whether frogs are more tolerant, more resistant or simply exposed differently. 12
• The findings are not evidence that chytrid explains declines throughout the Atlantic Forest. A separate analysis of 90 Brazilian amphibian species identifies climate change and extreme weather, including El Niño-related anomalies, as primary drivers across Brazil. Its broader scope does not settle the finding at Boracéia. 13
• The declines form part of a wider history of serious amphibian losses in the Atlantic Forest. A regional review places the peak in 1979, while the new study examines pathogen evidence at a single station. 41

Why this matters

The study adds evidence about a possible cause of an important local decline and about the later presence of many historically recorded species. Its limits matter: the cause of declines may vary across the region, and the apparent recovery does not resolve the status of every species. 1234

What happens next

The key unresolved questions are the status of the five species not found in recent surveys, the mechanisms behind the apparent tolerance pattern, and how disease interacted with climate and extreme weather elsewhere in the forest. The supplied reporting does not describe a follow-up study or conservation intervention. 123

What we know

• The study examined more than 370 preserved specimens from 17 species and sampled contemporary frogs at Boracéia between 2022 and 2024. 12
• The researchers found no detectable chytrid fungus in specimens collected before 1979; 58.8% of frogs in the 1980s post-decline sample tested positive. 1
• Recent surveys found 12 of the 17 historical species at the site. The Smithsonian account says most amphibian species appear to have recovered locally. 2
• The evidence linking chytrid to the declines is from Boracéia and cannot be extrapolated to the wider Atlantic Forest. 12

What we don't know

• The status of the five historical species not found in recent surveys remains uncertain. 2
• The study does not establish what explains the apparent tolerance pattern, including the possible roles of genetic change, exposure differences or other factors. 1
• It remains unclear how far the Boracéia findings apply elsewhere in the Atlantic Forest, or how disease interacted with climate and extreme weather across the region. 13

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