Rare corroboree frog given second chance

By Patrick Hsiao May 10, 2012
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Scientists are returning hundreds of corroboree frog eggs to the wild in the hope of boosting the population.

ITS STRIKING BLACK-AND-YELLOW mottled colouration makes the corroboree frog stand out, but you’ll have a hard time finding these critically endangered alpine amphibians in the wild.

But now, thanks to an ongoing conservation project, southern corroboree frogs (Pseudophryne corroboree) are getting a second chance. This month more than 800 eggs from a captive breeding program are being returned to Kosciuszko National Park.

Corroboree frog numbers have declined by more than 80 per cent in the last ten years. It’s a familiar story from around the world: the corroboree frog has been decimated, largely by the fatal chytrid fungus that first struck the species in the 1980s. The fungus is notoriously difficult to treat, attacking the frogs’ skin, respiratory and nervous systems.

A recent survey by the NSW Office of Environment and Heritage found only nine male corroboree frogs calling throughout their historic breeding area at altitudes of over 1300m, with just a single nest containing eggs.

“The frogs are important for managing invertebrate numbers in the sphagnum bogs they live in,” says Michael McFadden a breeder at Taronga Zoo in Sydney. “They are one of only three species that live at that altitude, including the alpine tree frog and common eastern froglet.”

Corroboree frog conservation plan

Since 2010, Taronga Zoo, Melbourne Zoo and Healesville Sanctuary joined forces to harvest both wild and captive-bred corroboree frog eggs and place them back it the native frog’s habitat in the Snowy Mountains.

On location in the mountains, the eggs are grown in above-ground water tanks to stop them from being infected by the common froglet, a species which has shown little effect from chytrid fungus, but which acts as a carrier of it.

In 2010, 47 eggs were placed at locations in Kosciuszko National Park, and in 2011 another 244 were deposited. The latest and last batch of 819 eggs will be placed in several re-introduction sites in the national park, which include both chytrid-affected and chytrid-free sites, in an attempt to overcome the impact of the fungus.

The NSW Environment Minister Robyn Parker told reporters this week that conservationists hope to see positive results from the earlier releases soon. They have already noted the appearance of adult males – which take 3-4 years to reach maturity – from the early egg batches, and are hoping to soon see positive results with females, which take longer to mature.

“We’re trying to get a large population out there and then have natural selection take place,” says Peter Harlow, manager of Taronga Zoo’s reptile and amphibian division. “We’ve found a ridge that is naturally chytrid-free and we’ve seen good success there.” 

Future of the corroboree frog

It is hoped the effort made over the past several years will have a significant impact on an ageing frog population. Corroboree frogs can become infected with the chytrid fungus before tadpoles even mature.

If they make it to adulthood, though, they have no natural predators, Peter says. “The frogs are toxic, which shows in their colours. They have no natural enemies – snakes don’t eat them and neither do crows.”

Experts describe the loss of frogs globally as the largest mass extinction since the dinosaurs, and the minister said every effort should be made to save them. “Frogs are accurate indicators of environmental health in our waterways,” she said.