Deadly Fungus Causes Ill Frogs to Leap Great Distances, Possibly in Search of Mates

The chytrid fungus is a lethal pathogen affecting amphibians amid an ongoing global crisis, capable of wiping out entire populations. Yet, for one endangered frog species in Australia, the infection has led to an unusual positive effect: significantly larger hops.

Verreaux’s alpine tree frog (Litoria Verouki Alpina) is impacted by the chytrid fungus, Batrachochytrium dendrobatidis. Those infected can leap nearly a quarter further than their uninfected counterparts.

“These findings remind us of the incredible resilience of these amphibians and their responses to threats from this daunting pathogen. Remarkably, their bodies can display unexpected adaptations,” says Teagan McMahon from the University of Connecticut in New London, who was not involved in the research.

Alexander Wendt and colleagues at the University of Melbourne, Australia, investigated the impact of Bd infection on the health of alpine tree frogs, using their locomotion as an indicator of physiological health.

In their laboratory study, the researchers separated 60 frogs into groups based on infection status. Wendt and his team assessed how the frogs responded to extreme temperature conditions and measured their jumping distances when gently stimulated.

Remarkably, six weeks after infection, the frogs that had contracted Bd exhibited an increase in jumping distance of nearly 24% compared to uninfected ones. Typically, in other amphibian species, energy reserves are drained as the immune system combats the fungus. The physiological responses to Bd can vary significantly among amphibian species, offering temporary advantages in cases of sublethal infections.

“However, as soon as clinical symptoms emerge, it becomes exceedingly challenging for most species,” Wendt notes.

The immune response of alpine tree frogs does not appear robust enough to hinder their reaction to Bd, suggesting that such enhancements may aid them in locating mates quickly before their condition worsens. Other frog species are also known to amplify their mating calls when infected with Bd.

This short-term bolstering of jumping ability can be advantageous when faced with Bd. “From an evolutionary standpoint, it makes sense,” McMahon adds. “Enhanced mobility may contribute to increased transmission rates and prolong the host’s lifespan.”

The influence of Bd on amphibians is increasingly recognized as being shaped by complex interactions between host biology, the fungus, and the surrounding environment. “All we can do is gather as much information as possible to assist these species in surviving and mitigating the spread of Bd before it reaches a critical point,” Wendt emphasizes.