A new species of forest frog has been identified in the Hunter Region, delighting conservation scientists working to help amphibians survive a pandemic specific to the creatures.
The southern stuttering frog (Mixophyes australis) grows to 7cm long and breeds in small streams in wet forests.
It looks like another species of frog called the stuttering frog (Mixophyes balbus) and has a similar mating call.
University of Newcastle Honorary Professor Michael Mahony said "for the last 60 years, scientists believed the two species were the same".
Genome testing, which has become feasible in the last decade, revealed they are different species.
University scientists made the discovery while investigating the susceptibility of frogs to a disease - a fungus known as chytrid.
The fungus, which has caused a 40-year global pandemic for amphibians, attacks the skin and produces a toxin that leads to heart failure.
The scientists placed automated recording devices along more than 50 streams where the frogs were once known.
They also went into forests to listen for the male frog's mating call - a song "that has reverberated along the streams for thousands, perhaps millions, of years", Professor Mahony said.
One spring evening, with glow worms on the exposed stream banks, the scientists heard the frog's call in the Barrington range.
"We were excited and also relieved," Professor Mahony said.
"We knew the frog used to occur there from our previous years of work. When we weren't finding it in many locations, it was a great relief to know it was still there."
Professor Mahony said the frog can also be found in the Watagan Mountains.
It had previously been known to live in the Blue Mountains and "down to Victoria", but populations had "completely disappeared south of the Hawkesbury".
This aligned with the fact that the disease "likes cooler, moist environments".
"We've got good evidence that the frogs north of the Hawkesbury have recovered. They declined from the 1990s onwards, but they're coming back," he said.
"We actually think they must have evolved some form of resistance. That's an area of active research."
Nonetheless, Professor Mahony found that the southern stuttering frog warranted listing as endangered because it had disappeared from about 50 per cent of its known range. Efforts are being made to reintroduce the species.
The university has also built habitat ponds in the Watagans to help the frogs survive.
"We're having some success. We're one of the few conservation biology groups worldwide that's achieving that," he said, adding a lot of people were working on the disease but few were devising solutions.
His laboratory was the first in the world to identify that a disease was killing frogs.
"We've been swabbing frogs for 20 to 30 years. We use PCR tests to tell whether they have the disease.
"We can't inoculate them, we don't have any vaccine. But we use the same technology for swabbing that was used in humans in the COVID pandemic."
Seven species of Australia's native frogs have gone extinct because of this disease.
The disease is threatening another 30 frog species with extinction in Australia, which has about 400 frog species in total.
Professor Mahony says understanding how frogs have developed resistance to the disease is "vital to saving them and possibly many others".
Numbers of the frogs with resistance can be boosted through improving the extent of their habitat.
He said frogs had been evolving for 2 billion years and are "part of evolution like we are".
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