New hope for endangered Australian rainforest frog

Numbers of a rare and elusive Australian rainforest frog appear to be recovering despite the presence of an infectious fungus that has wiped out other amphibian populations worldwide.

A team of researchers from Southern Cross University, led by Dr David Newell, has published its findings, ‘Population recovery following decline in an endangered stream-breeding frog (Mixophyes fleayi) from subtropical Australia’, in the open access peer-reviewed scientific journal PLOS ONE.

“We set out to assess the abundance of the endangered Fleay’s barred frog (Mixophyes fleayi) and whilst it remains missing or extremely rare at a number of historic locations, the populations we studied have now recovered,” said Dr Newell from the University’s Forest Research Centre in the School of Environment, Science and Engineering.

“What is most interesting about our work is that the recovery occurred in the presence of the pathogenic fungus, amphibian chytrid.”

The amphibian chytrid has been shown to be highly infectious and can kill frogs rapidly.

Globally, amphibians suddenly started to disappear from the late 1970s to early 80s.

“What was most perplexing about these disappearances was that they occurred in pristine streams from high elevation rainforests. The discovery in the late nineties of this pathogenic fungus in sick and dying frogs seemed to be the answer,” Dr Newell said.

Fleay’s frog (named in honour of naturalist David Fleay) is found in the Gondwanna World Heritage rainforests of southeast Queensland and northern NSW. Targeted surveys in the mid to late 90s revealed that the species was extremely rare and absent at previously known sites.

The researchers conducted monitoring at two independent streams: in the Border Ranges National Park and in the Nightcap National Park.

Frogs were captured, tagged and released periodically over seven years.

“We were able to mark the frogs with small transponder tags and follow their fate through time. Despite the presence of the amphibian chytrid, the populations that we studied increased in abundance up to 10 fold, from a period of extremely low abundance,” said Dr Newell.

“Frogs were very long lived. Some were present for more than six years and this may be central to the observed recovery.

“Despite the fact that eastern Australian rainforests have been a hotspot for amphibian extinctions and declines, there are very few long term data sets of this type published.”

The study’s co-investigators were Dr Ross Goldingay, a senior researcher in the School of Environment, Science and Engineering, and Dr Lyndon Brooks, a research statistician with the University’s Marine Ecology Research Centre.

“It is fundamental to conservation planning that we understand whether populations of endangered species are stable or not,” Dr Goldingay said.

“Here we have clearly demonstrated an increase in population numbers over time. We need to investigate further to understand whether this has alleviated the extinction risk for these populations.”

Dr Newell said the next phase of the research would be to understand how Fleay’s barred frog has been able to re-build its numbers.

“It is important that we continue this work because it suggests that there may be a change in the way that the amphibian host and pathogen interact.”

This study forms part of Southern Cross University's research in the field of zoology, which was given the highest possible classification of 'well above world standard' in the recent Excellence in Research for Australia (ERA) 2012 national report. The University's zoology research is focused on the impacts of environmental change – both natural and human induced – on animal species, including the impacts of land clearing, road building and urbanisation; how Australia's bird fauna has evolved and adapted over time; the impacts of climate change and ocean acidification on marine organisms. Zoology research is located in the University's School of Environment, Science and Engineering and in the Marine Ecology Research Centre and the National Marine Science Centre.

Photo: The endangered Fleay’s barred frog (Mixophyes fleayi). (Credit: D Newell)