Despite a deadly disease which has nearly wiped out the critically endangered Alpine Tree Frog from the Snowy Mountains, a new study has found the species is fighting back by breeding more when infected.
Chytridiomycosis, a disease caused by chytrid fungus, has eradicated more than 80 per cent of the Alpine Tree Frog (Litoria verreauxii alpina) population since 1980, and almost all infected frogs die after their first breeding season.
The species is now only found in isolated sites in the wild and new insights into their breeding habits may be the key to saving them from complete extinction.
Published today in Open Biology, the University of Melbourne study found chytrid infection leads to Alpine Tree Frog males fathering more offspring – 31 per cent more breeding events than uninfected frogs – and even appearing more attractive to potential female mates.
Lead author Dr Laura Brannelly, from the Melbourne Veterinary School, said the findings are counterintuitive to what people might expect to happen when an animal is infected with a disease.
"We anticipate a sick animal might be unable to reproduce while it saves its energy to fight a deadly infection, Dr Brannelly said.
"Surprisingly, our study has found the opposite to be true, and the frogs are funnelling their energy into spawning before they inevitably succumb to infection.
"It is this increase in reproductive effort that has allowed Alpine Tree Frogs to survive in the wild alongside the disease that has wiped out so many other amphibian species."
The study revealed the sperm of infected males was of a higher quality compared to healthy males, including producing more sperm volume and healthier sperm cells leading to higher fertility than uninfected males.
"We also found that infected frogs appeared more attractive to female mates than uninfected males, which again, seems counterintuitive." Dr Brannelly said.
The study found infected males produced more colourful displays in their throat patch, which is a signal to attract females, with females preferring brighter and more vibrant colour displays.
Chytrid is responsible for the decline in over 500 amphibian species and the extinction of at least 90 species, and Australian amphibians are particularly susceptible to chytridinfection.
The researchers hope the study will provide valuable insights into protecting critical breeding habitat to help conserve wild Alpine Tree Frogs, including constructing additional breeding ponds and improving connectivity between populations.
"Understanding how frogs survive in the wild will help us better manage them and stop them from going extinct. We know breeding is critical for survival and we can help these frogs by protecting current habitat and creating new breeding habitat, Dr Brannelly said.
"With our help and their ingenious survival strategy, it is our hope that the beautiful songs of the Alpine Tree Frog will be heard again across all of the Australian Alps."
