‘Like nothing in my lifetime’: researchers race to unravel the mystery of Australia’s dying frogs

Jodi Rowley, a scientist, was bringing frozen dead frogs to her door in the middle of Sydney's lockdown.
Sometimes, one may arrive dry and shrivelled in the post.

Shell packs them in ice and takes them to the Australian Museum. There, more green tree frogs, stripe marsh frogs, and the invasive canetoad are all waiting in a freezer to undergo genetic testing.

Rowley and her team are working with scientists from the Australian Registry of Wildlife Health Taronga Zoo and a forensic unit within the NSW department of planning and industry to unravel the mystery of why Australia's frogs are dying.

They have collected over 1,200 records of dying or dead frogs since late July. About 70% are in New South Wales, and 22% in Queensland.

Rowley stated that although we are dealing with our own pandemic, frogs are also facing a pandemic.

It's almost like nothing I have ever seen in my life.

Jodi Rowley, Australia Museum researcher, has sent Jodi one of the shrivelled Frogs. Photograph by Carly Earl/The Guardian

It really broke our hearts

Rowley is a conservation biologist who specializes in amphibians. He is also the chief scientist of Australian Museums FrogID. This citizen science project, which has been active for four years, focuses mainly on recording the calls from Australia's many frog species.

Its work changed after Rowley gave an interview to ABC Radio in late July about dead green tree Frogs found around Scotts Head, NSW's mid-north coast.

Rowley began receiving emails from Rowley about similar frogs being found in other parts.

Karrie Rose, head of Australian Registry of Wildlife Health wrote a piece for Conversation a week later. It asked anyone who saw sick or dying amphibians to report it through the FrogID email.

In 24 hours, they received 160 emails. Since then, they have received more than 2000 emails.

Some of these emails have been very distressing for me. It is hard to imagine what it must be like for those who see these frogs.

Rowley in her laboratory at work. Photograph by Carly Earl/The Guardian

One of these reports was from Yvonne Hulbert who owns a bed and breakfast located on Macleay Island, near Brisbane. There is a thriving frog population.

They have found dead and brown frogs on their property over the past few months.

They turn brown after turning a pale beige to fawny. Hulbert stated that they can become dry and then become emaciated, then shrivel and become bones.

The same frogs are recognized by us all. They slowly decline in size and health, and then eventually their eyes become dull and they die. It's very sad.

Gail Wilson-Lutter has lived with her husband in Meerschaum Vale, NSW's northern rivers, for 36 years. Each night, frogs would enter the kitchen through a hole in the roof.

We keep the "frog-cuzzi", a small pool for them to use. They are great at killing spiders and other pests.

Wilson-Lutter observed that frogs were becoming more emaciated in recent months and were also changing their colouration or dying.

Wilson-Lutter said that it really broke her heart, as we love our frogs.

It is too early to make any conclusions

The scientists have received reports from 31 species in nearly every state and territory over the past two-and a half months.

There are 30 species of frogs that are native to the area, including endangered species such as the green and gold bell frogs, south bell frogs, and giant barred frogs. The cane toad is the only invasive species.

Sixty percent of the frogs that were found were green tree frogs. This is likely due to the fact that they are a common species in and around homes.

The frogs found alive are often lethargic, emaciated, and have red bellies and coloured spots on their skin.

Frogs die quickly and shrivel up quickly. Many have been discovered dark brown and withered after their deaths.

Jane Hall, Australian Registry of Wildlife Health Taronga Zoo. Photograph by Carly Earl/The Guardian

Because frogs are fast-decomposing and cryptic, it is extremely difficult to work with them. Jane Hall works with Rose at Taronga Zoo's Australian Registry of Wildlife Health.

They have been performing necropsies of frog carcasses at Taronga Zoo's pathology facility, which acts as both a morgue or a laboratory.

They take samples of their liver, blood, and stomach contents if possible, and dissect the frogs.

Rowley and her team at the Australian Museum are studying the animals at a molecular level.

They perform a Covid-19 test in the same way. They swab the frogs on their stomachs and legs, and take a small sample of their skin. The DNA test is then performed to determine if there are any pathogens.

The number one culprit for mass mortality is currently chytrid fungal, which has been responsible worldwide for the declines in more than 500 amphibian species.

It's more likely to occur during winter months when the frogs immune system slows down.

Although some tests returned positive results, Rowley and Hall say it's too early to draw any conclusions.

The field investigation process has been hampered by Covid-19 lockdowns.

Jodi Rowley's frozen samples have been sent. Photograph by Carly Earl/The Guardian

Researchers are working with a network vets in Australia to store frozen frogs, until they are ready for delivery.

Others will perform a basic necropsy, and then keep the carcass in a solution to allow for microscopical examination later.

Friends and family members also store frozen frogs left behind by residents of their communities in mailboxes.

A separate forensic team runs toxicology tests to find pesticides, heavy metallics and other environmental toxins.

Pesticides have been used in large numbers as a result the recent mouse plague. Hall believes it unlikely, but it must be excluded.

Scientists will be able to access more samples and more locations after the lockdown ends. This will allow them to do targeted surveys and expand their research. It also gives them the opportunity to build a larger syndromic picture that can help identify common threads.

Rowley believes it to be chytrid fungal disease.

She asks, "Why would it have such an impact now?"

It could be the cold, extreme winter or how it interacts with other stressors like not enough food, pollution, and lack thereof. It could be a new strain, or something imported from abroad.

Hall believes there is no better example of a pathogen changing than the current pandemic.

She says that pathogens are constantly looking for ways to improve the way they move and work in animals.

Chytrid can change so we will check to see if it is the chytrid that our frogs are used too or a new type.

Another important question that remains unanswered is whether animals are dying from the disease or from it. The cause might be something entirely different, such as a new pathogen.

She says that once we have a better understanding of these issues, we can move to the next level and determine how it spreads and its long-term effects on vulnerable amphibian populations in Australia.

They are probably the most reliable indicator of environmental health. They are not to be ignored.

They absorb the environment through the skin, so if there is anything wrong with the environment, the frogs will let you know.

Anybody who sees a dead or unwell frog should contact FrogID Project email at calls@frogid.net.au.