Seeing a dead frog is rare – they are secretive, their bodies decompose and are often snatched by predators.

But as autumn turned to winter last year and Rowley heard hundreds of reports of dead frogs across Australia, she quickly began the process of trying to find out what was killing them, an effort that has rolled into this year as a second wave hits.

One possible reason for the spike in deaths could be a record year of rainfall brought on by the La Niña cycle. Like those of humans, frogs’ immune systems weaken with cooler weather, at the same time as the chytrid fungus is thriving in cooler and damper conditions.

Having the fungus in their system isn’t necessarily a death sentence for most frog species, but they can die “pretty rapidly” when it builds up to levels where their skin can no longer breathe and drink, Rowley said.

“These wet summers and wet winters that we’ve been having, are most likely pretty bad news for frogs. We are really worried about frogs in Sydney. We’re super lucky to have the frogs we do have. We don’t want to lose anymore.”

A new study from James Cook University, released on Thursday, suggested variations in microbiomes – the bacteria, fungi, and other microorganisms on the frogs – may play a key role. Dr Donald McKnight, who co-authored the study, said the research might have implications for how conservationists mitigate the threat of the chytrid fungus.

“It may be that the presence of the fungus that causes chytridiomycosis actually causes antifungal bacteria to thrive ... or possibly only frogs with high levels of antifungal bacteria can survive high infection loads,” he said.

Karrie Rose from the Taronga Australian Registry of Wildlife, who has been working with Rowley on the frog deaths, said the latest mortality event is an example of the impact of widespread ecological changes on wildlife health.

“We’re seeing patterns of disease emergence in wildlife now after the floods, very similar to what we saw just after the bushfires,” she said.

“We’ve had pandemics in humans, so it’s not unexpected we’ll come up with similar events in wildlife ... they’re just coming more frequently and becoming more widespread than we’ve ever seen in the past.”

If you see a sick or dead frog, you can send details and photos to the Frog ID project via email: [email protected].

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