In winter 2021, Australia’s frogs suffered a mass mortality event. As temperatures drop, we are worried it might happen again – we need you to help monitor our frogs.

Personally, winter 2021 is one I will never forget. Stuck at home in COVID-lockdown, I sat at my computer and I spoke with and wrote to amazing people across the country who were sending in reports of dead frogs in response to our plea for information. Some sent before and after photos: a plump, healthy-looking frog poking out from a hanging plant on the balcony several months before, followed by that same frog upside down and already drying up, on the ground. Others reported coming home to find dead green tree frogs strewn around their deck. One farmer reported dead frogs strewn across the property, from sheds to paddocks. He’d not seen anything like it in over 40 years running the farm. It was heartbreaking.

Winter 2021 was devastating for Australia’s frogs. As soon as the first cold snap of the season hit, reports came in of an unusual number of sick and dying frogs. At the end of the winter there were over 1600 reports of sick and/or dead frogs. Unfortunately, that’s likely just the tip of the iceberg – the true death toll is likely magnitudes higher. Given the vital role frogs play in healthy ecosystems, from food webs to nutrient dynamics, the consequences could impact entire ecosystems.

Dead Striped Marsh Frogs (Limnodynastes peronii) in a suburban Sydney pond.

Dead Striped Marsh Frogs (Limnodynastes peronii) in a suburban Sydney pond.

Image: Vivienne Miller
© Vivienne Miller

Australia has 246 species of native frog, almost all of which are found nowhere else on Earth. Unfortunately, at least four of these species have already been driven to extinction, and another 40 are threatened. Frogs are being driven to extinction by habitat loss and modification, disease, and introduced species, and they are amongst the first species to respond to a changing climate. Things were already extremely precarious for Australia’s frogs before they started dropping dead at people’s doorsteps in 2021.

Reports came in from every state and territory, but the mortality appeared most intense along the East Coast, from southeast Queensland to the South Coast of New South Wales. Although Green Tree Frogs (Litoria caerulea) were the most commonly reported frog species, at least 46 species were reported sick and dying. That’s almost a fifth of all Australian frog species! Four nationally threatened frog species were also reported: the Giant Burrowing Frog (Heleioporus australiacus), Green and Golden Bell Frog (Litoria aurea), Southern Bell Frog (Litoria raniformis), and Giant Barred Frog (Mixophyes iteratus). The true spatial extent and number of species impacted is likely much larger than reported, extending into remote and protected areas where people were unable to observe these animals, and likely affecting other rare, threatened, or difficult to detect frog species.

These reports triggered an emergency response and collaborative investigation. We frantically manned the phone and email. We helped coordinate people transporting sick frogs to vets and asked them to store any dead frogs for us, so that we could test when travel restrictions allowed us to pick them up. As soon as we could, we collected these dead frogs and worked with Taronga’s Australian Registry of Wildlife Health and colleagues across the country to investigate the cause. Our team also began conducting intensive surveys of frog populations in the wild. We were desperate to understand the extent, cause and impact of this frog mortality event.

The Australian Museum team conducted frog surveys across New South Wales to understand frog population health.

The Australian Museum team conducted frog surveys across New South Wales to understand frog population health.

Image: Jodi Rowley.
© Jodi Rowley.

We have now tested over 500 dead frogs of dozens of species for our number one suspect, the amphibian chytrid fungus (Batrachochytrium dendrobatidis). This pathogen has been implicated in the declines and extinctions of frogs around the world for decades, so it was the obvious thing to test for. While we can now confirm that the amphibian chytrid fungus played a significant role in the 2021 frog mortality event, a relatively large proportion of dead frogs did not test positive for this potentially lethal pathogen, suggesting that it may well have been acting alongside another pathogen, toxin or environmental process. It turns out this is far from a simple story. We continue our investigation, working with colleagues to unravel the deadly mystery – one suspect at a time.

Last winter, we feared a repeat frog mortality event, but thankfully, although we did receive reports of sick and dead frogs throughout the winter, it was nothing like the previous year. Whatever precipitated the mass mortality of frogs in 2021 did not appear to do so in 2022. We hope that continues this winter and that as temperatures drop we won't find any dead or dying frogs en masse in Australia. But we need your help to keep watch.

To help us monitor the health of our frogs this winter and detect and respond to any mass mortality of frogs (should it occur), please keep a look out for any sick or dead frogs and report them. Signs of a sick frog include lethargy, a frog lying out in the open during the day, and discoloured (often dark) or patchy skin. If you see a sick frog (or frogs), please take a photograph and send the photo with your location to the Australian Museum’s citizen science project FrogID via

Sick Green Tree Frog (Litoria caerulea). In winter 2021, sick frogs were often lethargic, sitting out in the open during the day, and had dark, patchy skin.

Sick Green Tree Frog (Litoria caerulea). In winter 2021, sick frogs were often lethargic, sitting out in the open during the day, and had dark, patchy skin.

Image: Liz Davis.
© Liz Davis.

Please consider donating to help support our ongoing investigation into the cause and impact of this mass mortality event, and our monitoring of frog population health. Please also download the free FrogID app and record calling frogs whenever you can, which will contribute to our overall understanding and conservation of Australia’s frogs, including the impacts of the winter 2021 mortality event.

While 2021 was a tough time for Australia’s frogs, that same winter also demonstrated that people across Australia do care about our frogs, and that together, we can make a difference. This winter, please continue to keep our frogs on your radar.

Dr Jodi Rowley, Curator, Amphibian & Reptile Conservation Biology, Australian Museum Research Institute & UNSW Sydney

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Thank you to everyone who has donated, and to all the people that took the time to report sick or dead frogs, transport sick frogs to vets or stored dead frogs for us to collect, you went above and beyond for our frogs, and we are forever grateful. To everyone that records calling frogs with the FrogID app, thank you- every FrogID recording makes a big difference to our understanding of our frogs and how they are responding to droughts, fires, floods and disease. Thank you also to the entire Australian Museum Herpetology Team, Taronga’s Australian Registry of Wildlife Health and all our collaborators across the country – too many to count.