Australia frogs 'could be wiped out by killer fungus'

Northern corroboree frog Image copyright Michael McFadden / Taronga Zoo
Image caption The northern corroboree frog is one of seven species of Australian frog under threat of extinction

Seven Australian frog species on the verge of imminent extinction due to a deadly fungus could be saved with urgent intervention, scientists say.

These species have wild populations of fewer than 2,000 frogs and face an "ongoing state of decline".

The spread of a deadly chytrid fungus will likely worsen their plight, a study in Wildlife Research says.

The southern and northern corroboree frogs, famous for their black and yellow bodies, are among the species.

The list also includes the armoured mist frog from Queensland and the Tasmanian tree frog.

"These are some of the most ancient lineages in the Australian fauna," says co-author Dr David Newell, an environmental scientist at Southern Cross University. "Most are found nowhere else on the planet.

"The rapid decline and disappearances in recent decades is therefore alarming given some species have remained unchanged for millions of years."

Image copyright Michael McFadden / Taronga Zoo
Image caption Zoos Victoria estimates that there are only 100 southern corroboree frogs left in the wild

Dr Newell is part of a team of scientists calling on the federal government to provide A$15m ($11.3m; £8m) in funding over five years, to develop a national research effort to investigate the deadly chytrid fungus that has been killing Australian frogs for more than three decades.

In their paper, they outline a strategy for preventing the extinction, which involves wide-ranging surveys and monitoring, captive breeding programmes, possible relocation of frog populations to climatically suitable regions, and more research to understand the deadly fungus.

"Extinction is forever. What price can you put on the loss of an entire species? We are asking the federal government to act and support the research that is urgently needed ... because the threat posed by the amphibian chytrid fungus is far from over," Dr Newell tells the BBC.

"The next few years provide the last chance to save the most endangered frogs in Australia from extinction caused by chytridiomycosis," the researchers write.

A deadly fungus

While habitat loss continues to be a major threat for amphibians globally, Dr Newell says the major culprit for the decline of frog species throughout Australian has been the deadly chytrid fungus.

This fungus attacks the parts of a frog's skin that have keratin in them. Since frogs breathe and absorb salts through their skin, these infections are particularly problematic. They make it difficult for the frog to breathe and balance salts in their body, and ultimately cause the heart to stop functioning.

Image copyright Jodi Rowley/Australian Museum
Image caption The gastric brooding frog, which incubated its young in the mother's stomach, was the first species killed off by the chytrid fungus

Dr Newell says this fungus was first introduced into Australia near Brisbane in the late 1970s, and soon led to the extinction of the gastric brooding frog. These curious frogs incubated in the stomachs of their mothers, and birthed via regurgitation.

Globally, the fungus has caused the "severe decline or extinction of hundreds of amphibian species," the authors write. In Australia, it is suspected that six frog species have already been killed off by the fungus.

Can it be stopped?

"Some species have recovered after initially being exposed to chytrid and having suffered population crashes," says Dr Newell. "If we can study the mechanisms that have allowed this to occur, then we may have some hope."

The disease also affects certain frog species differently: some succumb in a matter of weeks after exposure, while other species can carry the fungus for long stretches with no ill-effects.

Dr Newell says this may be a "natural immune response occurring" which could be applied to other at-risk species.

He also says there is evidence to suggest frogs face heightened risks of infection and death during their transformation from tadpoles into young frogs.

Raising frogs in captive breeding programmes until they have passed this critical stage is one option to maintain wild populations, he says.

'A lot of work to be done'

Dr Jodi Rowley, an amphibian biologist at the Australian Museum in Sydney, says it is encouraging that some species have shown resilience against the fungus and certain infected populations have been able to recover.

Still, she says long-term funding for a co-ordinated effort will be important for any frog conservation strategy moving forward.

She says the chytrid disease is so devastating because, once it is there, it is almost always present in the environment, and easily transmissible through contact with infected water.

"It can be at low levels for extended periods, and then there's a huge spike causing population declines," she says.

But in Central America, which has also been hard-hit by the fungus, conservationists have discovered populations of frogs believed to be extinct.

"There is a chance, and I've got my fingers crossed, that if we do intensive surveys in areas of Australia where the missing frogs were found, we may be able to rediscover some populations that are still hanging on," she tells the BBC. "I would love for that to be the case."

She says the drier edges of the habitats where the frogs lived might be good places to search, away from the conditions in which the fungus thrives.

"There is a lot of work to be done if we're going to save these frogs," she says.

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