Watch: Frogs threatened by mysterious skin disease may be protected by 'frog hotel' and 'frog apartment blocks' in suburban backyards

Last winter, scientists at the Australian Museum received hundreds of reports of dead or dying frogs across the country.

Seen to be slow, thin, and darker than usual, the frogs were identified to have been suffering from amphibian chytrid fungus.

The condition is a known pathogen that attacks the frog's skin and has been endemic to amphibian populations in Australia for several decades.

But only over the last couple of years has the virus caused the death of so many species, and experts aren't sure what's causing it.

Frog biologist Dr Jodi Rowley described the disease as "the Achilles' heel of frogs."

"[Frogs] use their skin to drink and to breathe, and so anything that attacks their skin can have serious consequences for them," Dr Rowley said.

"So we know that this disease is involved, but we're not yet sure why now that would be causing such an issue."

Over the summer, the casualties seemed to stop, leading researchers to believe last winter's fatalities were just an anomaly.

But, as the weather has turned cold again this year, more reports of frog fatalities have been made.

Last year, during the COVID-19 pandemic lockdowns, researchers were unable to attend the sites where frogs were being reported as sick and dying.

So field work is being done this year to determine the cause of the frog fatalities.

In particular, the researchers are getting out to check on the often hidden, rare frog species that exist beyond the perview of the average citizen scientists.

"We're trying to rule out all sorts of other diseases at the moment, as well as toxins, pesticides, things like that," Dr Rowley said.

"So we are still investigating it. What was right was that the frog stopped dying as the weather got warmer and over."

Over 40 different species of frogs, and cane toads, were reported as sick or dying last year.

The iconic green tree frog has been the most commonly reported, but Dr Rowley believes that may be because they are the most recognisable species affected by the disease.

"We're not too sure if that's just because they're the ones that you tend to see," she said.

"We know it's quite widespread and what we're particularly worried about is the species that maybe people wouldn't have come across. So those in national parks, small ones, threatened [species], rare frogs.

In addition to helping the researchers identify problems areas, frog biologists are also encouraging Australians to build shelters in their backyards that may help frogs survive the onslaught of winter weather.

"So people think usually when they want to help frogs out in their backyard, you will [need to] build a pond. And that is a fantastic way to help frogs out. Frogs need ponds with fresh water in it too breed," Dr Rowley said.

"[But] during the day, frogs need a place to sleep. And also during winter, frogs bunker down and sleep for months."

'Frog hotels' can be made using PVC pipes, old bathtubs, bamboo and vegetative materials.

"They're just basically a lovely shelter site for frogs to hang out in [...] Anything where tree frogs in particular with those sort of sticky toe pads can get inside and shelter and be safe and dark and slightly humid," Dr Rowley said.

"It's a really great way to give frogs a hiding spot and they might in fact take up residence. So it's more like a tree frog apartment block than a hotel."

The researchers are also fearing that the death of so many frogs might indicate a wider problem affect many different animal species.

The frogs themselves may be the visible symptom of a much larger ecological crisis.

"Well, frogs are really sensitive to any kind of environmental change and they are sort of the canaries in the coal mine or a bellwether of environmental change," Dr Rowley said.

"When frogs start to disappear, then we should definitely be worried. Even though frogs themselves, you might think they're kind of small and not that important, they actually perform a really big role in healthy ecosystems. And actually they should be really, really abundant."

A thriving frog population is indicative of a healthy food chain.

"When the frogs disappear, all the other animals that rely on frogs for food, birds, mammals, reptiles, they start to disappear as well," Dr Rowley said.

"And the streams and ponds clog up with algae because the tadpoles are usually in these places munching away on algae.

"So they do seem to have really big and irreversible consequences on healthy ecosystems and an almost selfish front, they also help keep mosquito populations down.

"And they also eat a lot of pests species as well. So we really do want frogs around and we should be alarmed when they're disappearing."

To assist in the nationwide frog count, visit FrogID.net.au.