In a surprising twist amid a global amphibian pandemic, infected Verreaux’s alpine tree frogs in Australia jump nearly 24 percent farther than healthy ones, possibly to find mates before the disease proves fatal. Researchers suggest this enhanced mobility could aid both reproduction and fungal spread. The finding highlights species-specific responses to the chytrid pathogen Batrachochytrium dendrobatidis.
The chytrid fungus, known as Batrachochytrium dendrobatidis or Bd, has devastated amphibian populations worldwide since its emergence. In the case of Verreaux’s alpine tree frogs (Litoria verreauxii alpina), a threatened species native to Australia, infection leads to an unexpected physiological boost rather than immediate debilitation.
Alexander Wendt at the University of Melbourne and his colleagues conducted a lab study with 60 frogs, split into uninfected and Bd-infected groups. They assessed responses to temperature extremes and jumping distance after gentle prodding. By the sixth week after infection, the infected frogs leapt nearly 24 percent farther than their uninfected peers.
This contrasts with typical effects in other amphibians, where the immune system's fight against Bd drains energy reserves. "[The findings] remind you how resilient these amphibians are and how they are dealing with the bombardment of this really horrible pathogen. And yet, their bodies are able to do something miraculously unexpected," says Taegan McMahon at Connecticut College in New London, who was not involved in the research.
Wendt notes that while sublethal infections may offer temporary benefits, outcomes worsen once clinical signs appear. "But once clinical signs appear it’s usually a nail in the coffin for most species," he says. The jumping enhancement might enable infected frogs to seek mates for a final reproductive effort, similar to how some species amplify calling behaviors when infected.
From the fungus's perspective, increased movement could enhance transmission. "Evolutionarily, it would make sense for [Bd] to facilitate movement so that it’s getting a higher level of transmission and more longevity in a host," McMahon explains. Bd's impacts vary by host biology and environment, underscoring the need for targeted conservation. "All we can do is learn as much as we can to help species survive and to slow or stop the spread of Bd before it’s too late," Wendt adds.
The research appears in Animal Conservation (DOI: 10.1111/acv.70042).