By Peter Hannam 15 July 2018 Scientists and volunteers, out in the wilds of Kosciuszko National Park, have a surprisingly simple way of telling if any rare frogs in their care are around. "Hey frog!" they typically call out. Males of the critically endangered southern corroboree frogs dutifully croak back in reply. “The males compete via calling to attract females," says Andrew Elphinstone, manager of conservation and recovery programs at Taronga Zoo. "Any sort of noise, they think: 'Hey, I got a response.' ” If only securing the survival of this stunningly beautiful black and yellow amphibian were as easy. As far as anybody knows, as few as 50 adults of the species survive in the wild. Even those are located in a handful of special enclosures built at three locations in the park. The Office of Environment and Heritage first began efforts to save the southern corroboree frog in 1997 and Taronga Zoo joined the cause in 2006. Over the years, thousands of eggs, tadpoles and juveniles have been bred in captivity and released into the seven metre-diameter "frog resorts". "I'm 100 per cent sure that without intervention, this species would be extinct," Nick Boyle, Taronga Zoo's manager for conservation, health and welfare, said. The main threat is the deadly chytrid fungus, which has smashed amphibian species worldwide, perhaps pushing as much as 150 species to extinction, including six in Australia, said Michael McFadden, supervisor of Taronga's herpetofauna unit. The disease, possibly originating in south-east Asia, disrupts animals' salt levels, triggering cardiac arrest. Conservation efforts around the world are increasingly focused on interventions to help threatened species cope with challenges such as a changing climate, the loss of habitat and pollution - stresses that can often make them more vulnerable to disease. Taronga - along with partners such as Zoos Victoria - is working to hone breeding techniques to create an insurance pool of individuals of species at risk. That population can then be tapped to be reintroduced to the wild. Jodi Rowley, a frog biologist with the Australian Museum and the University of NSW, said conservationists always have a battle to decide which species to prioritise for rescue efforts, but the beauty of the southern corroboree frog is one factor in its favour. "It might be that they are just gorgeous," Dr Rowley said. "They're like little lollies." The frogs - including the similarly endangered northern corroboree frog - are more valuable than aesthetics alone, providing a critical role in maintaining healthy ecosystems. They help keep mountain streams free of algae, eat insects such as mosquitoes and provide food for birds and reptiles and other creatures. "They're tasty protein packages," Dr Rowley said. Australia has some 240 frog species, including 35 in the Sydney region, with new ones still being discovered. Nationwide, though, four species are already extinct, five are critically endangered, 14 are endangered and 10 are vulnerable, she said. Taronga's efforts to work out how to breed the frogs, then determine the best age to release them, and to foster population recovery, are already benefiting other species including frogs. For instance, in 2009 a farmer near Yass brought to Taronga a handful of what turned out to be yellow spotted bell frogs, a species though to have been extinct for three decades. Years of attempts to breed the frog in captivity finally resulted in 200 juveniles being able to be released in March this year into a stream in the southern highlands. By October another 500-600 are likely to be released, Mr Boyle said. “The two species of corroboree frogs are incredibly striking but we’re happy to look after the small brown jobs [like the yellow spotted bell frogs] as well,” he said, adding the real heroes behind the scenes are the zoo-keeping team. “They’re the ones who cracked the breeding and the management techniques for this species and learned how to look after them in a zoo-based environment so that we could actually establish an insurance program from the start,” he said. Bringing back the bilby Taronga's breed-to-release programs now number about 18, and include animals such as the bilby. The marsupial is presumed extinct in NSW after rabbits arrived to occupy their ecological niche and then predators like foxes and cats combined to cut their range by some 80 per cent over the past 200 years. As many as six new sites with predator-proof fences are being developed in inland Australia, and demand is high for bilby numbers to repopulate them. “They need 500-600 bilbies to found all those sites but there are not enough bilbies to go around," Mr Elphinstone said. So far, Taronga's Western Plains Zoe near Dubbo has just six of the animals, but the aim will be to build the number to 20 as a base to create a breeding base of 100. With a gestation period of just 12-14 - among the shortest for any mammal - that range may not take long. Mr Elphinstone said he wants to take advantage of the zoo's 1200-hectare spread to create "a centre for conservation excellence with a focus on NSW and and semi-arid zone species". Unfortunately, there's probably no shortage of such species needing some help.