Good luck Dua Leaper: scientists return frogs wiped out by fungal disease to wild | Canberra

Scientists have reintroduced green and golden frogs to the Australian Capital Territory for the first time since the species went locally extinct four decades ago.

The first cohort of 25 frogs was released Tuesday morning, an important step for the conservation of these animals, whose numbers have been devastated by the chytrid fungal disease which has wiped out 90 species of amphibians in 50 years.

Associate Professor Simon Clulow of the University of Canberra, one of the researchers who led the project, said it was “pretty incredible and really meaningful to come back [the species] returning to this region for the first time in almost 50 years.

“As far as we know, he’s missing [in the ACT] around 1981,” he said.

The 25 frogs, released at Mawson Ponds, are around 14 months old and have been immunized against chytridiomycosis, a disease caused by two fungal species.

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Tuesday’s reintroduction was the first of around 15 releases into wetlands around Canberra, which will total around 375 frogs.

Each frog is microchipped and even named, with the help of volunteers involved in the project. “We’ve had some creative ones,” said Dr Jarrod Sopniewski, a postdoctoral researcher at the University of Canberra. “We have a James Pond and a Dua Leaper.”

To give the amphibians the best chance of survival, the team dug 60 “frog spas” – four at each wetland site – and also installed 180 “frog saunas”.

Frog saunas and spas “would provide small pockets of refuge from disease in wetlands for the offspring that would ultimately be produced, because of course the offspring are not immune,” Clulow said.

Frog saunas – in this case, Plexiglas pyramids covering a three-tiered tower of black-painted bricks – are expected to provide refuge for frogs at temperatures that are lethal to chytrid fungi.

“The pathogen itself is very sensitive to high temperatures – it doesn’t like temperatures above 25°C; 27 or 28°C is quite fatal to it,” Clulow said. “A lot of Australian frogs… prefer these temperatures – the green and gold frog likes to be around 30C.”

Sopniewski said sauna trials had been installed for more than a year in Canberra. “Even when temperatures barely reach 10°C here, we are still [passively] entering your twenties on a sunny day.

The green and gold bell frog grows up to 8.5 cm in length and spends most of its time near ground level. Once common along the east coast of Australia, it is considered endangered in New South Wales.

Despite the devastation caused by chytrids, green and golden frogs have been observed surviving in isolated pockets along the East Coast, often in areas with slightly higher water salinity, Clulow said.

Building on this finding, scientists have installed satellite ponds around large wetlands – what they call “frog spas” – in which the water is slightly saltier. A salt concentration of about three parts per thousand “is more than enough to negatively affect the chytrid, but it is perfectly acceptable to frogs,” Sopniewski said.

The goal is to have 200 frogs on each of the 15 sites. “A female can have up to 8,000 eggs, so her population growth should begin very quickly if our chytrid interventions help these initial founders survive and reproduce,” Sopniewski said.

“It’s almost like you’re letting your kids discover the world themselves,” he added. “A little intimidating, but extremely exciting.”