Despite a rising number of amphibian extinctions in northern rivers rainforest catchments, one little frog is making a surprising comeback, according to Southern Cross University researchers.
Even more perplexing, the populations of the endangered Fleay’s barred frog appear to be recovering despite the presence of an infectious fungus that has wiped out other amphibian populations worldwide.
Dr David Newell from the SCU’s Forest Research Centre set out to assess the abundance of Fleay’s barred frog (also known as Mixophyes fleayi) and discovered that while it still remains missing or extremely rare at a number of historic locations, the populations they studied have now recovered.
‘What is most interesting about our work is that the recovery occurred in the presence of the pathogenic fungus, amphibian chytrid,’ said Dr Newell
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 Gondwana 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 rebuild 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.’
The findings, outlined in the paper ‘Population recovery following decline in an endangered stream-breeding frog (Mixophyes fleayi) from subtropical Australia’, were published in the open access peer reviewed scientific journal PLOS ONE.