Frogs' disappearance baffles scientists
Australian scientists have joined an international effort to attempt to solve a worldwide environmental mystery: a drastic decline in frog numbers.
Researchers are concerned that even frogs in pristine areas of rainforest are continuing to die for no apparent reason.
But the decline in frog numbers could be a warning of a much more serious ecological problem.
At a field research site on the Atherton Tablelands in north Queensland, scientists are searching for clues to why frogs are dying.
Richard Rettallick from Queensland Parks and Wildlife says the frog decline is an "absolute mystery". "In the world, north Queensland, especially the wet tropics here, is one of the hardest hit [areas] that we know of," he said. "[The] number of species gone missing and the population declines have been most dramatic."
Frog populations worldwide have been declining for the past 20 years, some to the point of extinction. Mr Rettallick says the study team in north Queensland has found that frogs have gone missing from upland streams but are still present in lowland streams.
"So what we thought we'd do is to bring frogs back to the upland streams and to watch them and see what happens, see if they die again," he said.
Every week, the frogs - which have been placed in enclosures - are weighed and measured.
"If the agent that killed the frogs 10 years ago in this area is still operating, this little guy should die soon," Mr Rettallick said.
After years of research, scientists believe at last they may have pinpointed one agent that has been killing frogs in Australia. Rick Speare from James Cook University says there is "one single pathogen that has emerged as probably quite the most significant cause of frog declines and that's a fungus".
"It really only appeared in Australia probably in the late '70s," Dr Speare said. "We've tracked it back to south-east Queensland in December '78, at the moment.
"Then our evidence indicates that it actually spread from south-east Queensland progressively up the Queensland coast." At the CSIRO animal health laboratory in Victoria, scientists perform autopsies on frogs from around the world in an effort to discover what killed them.
It was here that they identified the fungus killing Australian frogs. But they say that overseas, viruses are affecting frog populations.
"There were no recorded cases of the fungus being in vertebrates, that is, animals with backbones," according to the CSIRO's Alex Hyatt. "It was a first - it hadn't been described before. In Australia, the frogs have been susceptible to a fungus and that's the major cause for frog declines in this country.
"But overseas, say in America and in the United Kingdom, viruses are a major problem."
Are humans causing the decline?
Source: 1999 Australian Broadcasting Corporation Adapted from Genevieve Hussey's report on 7:30 Report on January 19, 2000.