After 10 years of captive breeding, the critically endangered corroboree frog might be on its way back from the brink of extinction.
Most of the frogs currently in the wild are the result of previous captive releases. But, this month, thousands of eggs bred in captivity at Taronga Zoo in Sydney and Zoos Victoria are being released into the wild — the largest release to date.
Last week the first batch of about 1,850 was released, with the rest planned for release in coming weeks.
“The eggs we released this month will take six months to metamorphose into frogs and then four years for them to mature,” said Taronga native fauna curator Michael McFadden. “It’s hoped that these eggs will contribute to giving this species a chance to recover.” The team released some of the eggs into raised pools that have been constructed to keep the deadly chytrid fungus out.
Others were released into natural pools in areas that are known to have low levels of the fungus and others were released into enclosures.
The fungus causes a disease called chytridiomycosis on the skin that fatally impairs frogs’ ability to maintain electrolyte, water and oxygen levels.
McFadden told Guardian Australia the program appeared to be working, since most of the adult frogs they saw in the wild were in areas where they were previously extinct but have since been reintroduced.
The frogs that are being bred are from stock that would have been exposed to the fungus for a long time and so might have acquired some resistance to it, said McFadden. “Long term, the disease is always going to be in the wild so they’re going to have to develop resistance,” he said.
McFadden said there were two published cases of Australian amphibians developing resistance to the fungus and another convincing anecdotal case. He said he was confident that, with enough help, corroboree frog would survive in the long term.
The disease has spread around the world, wiping out hundreds of species of amphibians. McFadden said the silver lining was that meant there were researchers everywhere working on ways to abate the disease.
At just three centimetres long, the corroboree frog is dark with spectacular yellow stripes and produces a poison that can kill predators.
Chytrid fungus is thought to have been introduced to Australia in 1970s, after spreading from either Africa or south—east Asia, where amphibians appear to have a natural immunity. It has spread in six continents and has been blamed for causing decline or extinction of 200 frog species .— © Guardian Newspapers Limited, 2016
