Frog population hops back
A TEAM of Southern Cross University researchers have found evidence of a rare Northern Rivers frog bouncing back from a fungal infection that has decimated amphibian populations around the world.
The researchers, led by Dr David Newell, looked at the endangered Fleay's barred frog in a seven-year study at the Border Ranges and Nightcap national parks, to see how it had reacted to the highly infectious chytrid fungus, which began wiping out amphibian populations from the late 1970s to the early 1980s.
"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.
Dr Newell said over seven years the research team had seen the frog population recover - although the species remained rare.
"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," he said.
"Frogs were very long lived. Some were present for more than six years and this may be central to the observed recovery.
"What is most interesting about our work is that the recovery occurred in the presence of the pathogenic fungus, amphibian chytrid.
"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," he said.
The team's findings have been published in the open access peer-reviewed scientific journal PLOS ONE.