For the second winter in a row, native frogs have been found dead or dying across Australia with scientists baffled as to why.
Biologist Jodi Rowley from the Australian Museum and University of NSW said while a deadly fungus had been harming native frog species, it was unlikely to be the sole cause of the latest mass deaths.
"We know that the amphibian chytrid fungus is involved," she said.
"This is a fungus that has been affecting frogs for several decades. They are dealing with their own pandemic.
"But we don't think it's the whole story because it has been around for a while.
"It is causing frogs' deaths, but not to the scale we have been seeing last year and we are hoping we don't see it as bad this year, but we are worried."
Mid North Coast a frog fatality hotspot
While frogs have been found unwell and dead across the country, Dr Rowley said the issue had been heavily reported on the east coast of Australia, particularly throughout New South Wales.
She said green tree frogs especially were struggling on the Mid North Coast of NSW, which was a "hotspot" last year.
During the past two winter seasons, Dr Rowley has collaborated with The Australian Registry of Wildlife Health at Taronga Zoo, and other conservation bodies, to investigate what was threatening native frogs.
She said it had been like trying to solve a "murder mystery".
"Certainly, if a frog is going to die, it will happen once it gets cold because their immune system really slows down," Dr Rowley said.
"We're exploring all kinds of potential pathogens, all kinds of diseases.
"We're doing lots of different tests and looking at things such as toxins and other stressors to try to rule things in and rule things out, to figure what is behind this awful mortality event."
Another 'rough' winter
According to the Australian Museum's latest FrogID report, at least four known Australian frog species have become extinct, with other species on the edge of extinction.
More than 20 per cent of 240 known frog species are considered threatened in Australia.
Dr Rowley said it was crucial that scientists worked out the cause, as the amphibians were an important part of a healthy ecosystem.
"They eat a lot of invertebrates including pest species, and tadpoles eat algae and also compete with mozzies," she said.
Dr Rowley said there were 1,800 reports of dead or dying frogs last winter, but believed the true extent was much greater.
"We know thousands of frogs have died, and that's just the ones we have seen," she said.
"Most of the frog reports we are getting are from people's backyards, from around suburbia in town where people see frogs in unusual places.
"But most frogs are probably dying in the bush out of our sight, and endangered species are probably not getting reported as much because they are rare and hard to find.
"If you do see a frog that is being a bit weird and sitting out in the open when it should be sleeping, do pay attention and report it to us if you can."
