The study, recently published Open Biology, paints a really exciting picture. Alpine tree frogs, once on the brink of extinction due to deadly chitrid fungus, now breed all year long—happy testimony to how successful such efforts can be. Dr. Jodie Brannelly has spent the past 12 years researching these endangered amphibians. She found that infected male Alpine tree frogs not only produced greater quantities of sperm but sperm of higher quality, causing them to breed in far more breeding aggregations than their uninfected counterparts.
Alpine tree frogs are listed as endangered in New South Wales and critically endangered in Victoria. The Commonwealth recognizes them as vulnerable. Their populations have severely declined due to a variety of threats, including climate change impacts, bushfires, and drought conditions. This research provides evidence that infected frogs are able to temporarily increase their reproductive investment. The total population size in each of the eight currently-known habitats is still unknown.
Breeding Dynamics in a Changing Environment
Specifically, the research found that male Alpine tree frogs with a chytrid fungus infection took part in 31% more breeding events compared to uninfected conspecifics. This fungus wreaks havoc on their skin and respiratory systems. Dr. Brannelly noted, “Our research shows infected animals are increasing their breeding effort and ultimate output. That increased breeding is able to offset the mortality that the disease is causing, which is allowing the population to survive.”
This unexpected and highly unusual reproductive behavior begs amateur naturalists and veteran environmentalists alike to consider the long-term sustainability of the species. Dr. Brannelly added that although boosting reproduction might ensure that the frogs survive in the short term, it is not a permanent solution to the frogs’ plight. “So while breeding seems to be helping them persist and survive right now, it’s probably not a long-term strategy,” she stated.
Hear from Dr. Brannelly’s colleague, Nick Clemann, as he reflects on the effects of chytrid fungus. This invasive pathogen has changed the game for these frogs, as he describes here. “The disease has changed the game in all the wrong ways,” he remarked. He pointed out that understanding these changes is vital for conservation efforts, stating, “Any information that can help us understand is something we can potentially use against the fungus to try and keep the animals in the landscape.”
The Impact of Chytrid Fungus
Chytrid fungus is one of the greatest threats to amphibian populations around the globe, ravaging amphibians like the Alpine tree frog by eating away at their skin. By inhibiting their normal breathing function, this attack increases mortality rates. The evidence produced in the present study has shown clearly that these frogs are somehow coping in a highly atypical manner.
Dr. Brannelly explained that the increase in breeding could be seen as a counterintuitive response to infection: “These animals are able to persist in some way due to increased reproduction which is weird and counterintuitive.” Infected males are redirecting their efforts away from maintenance and towards reproduction. This resolve allows them to raise even more young even while fighting the disease’s life-altering symptoms.
From the researchers’ point of view, the Alpine tree frogs are on a knife’s edge. Frogs like the Southern Corroboree Frog once flourished in hundreds of sites spanning from Mount Baw Baw to Kosciuszko National Park, researchers emphasize. In recent years, the invasive chytrid fungus has wiped out entire populations.
Future Outlook for Alpine Tree Frogs
This study does a tremendous job pointing out the specific phenomenon of Alpine tree frog behavior. It further illustrates the immediate need for conservation actions. Their future is very much in question as they continue to experience environmental stresses due to climate change and habitat destruction.
Dr. Brannelly cautions that treating the increased reproduction as a silver bullet won’t be enough to keep these frogs making it long term. Their existence hangs on a delicate balance, with “all of their eggs in this one basket, literally,” as she puts it.
Conservationists argue that there’s still a need for more research and more proactive measures. The positive results from this study will assist in designing better strategies to fight chytrid fungus. They want to keep the current populations of Alpine tree frogs in their natural alpine habitats.
