Frogs’ Great Escapes

Life in the wild isn’t easy. We’ve all seen enough nature videos to understand that it’s literally an organism-eat-organism world out there. But those that are preyed-upon do have tricks up their sleeves, er, arms or wings, that help them avoid predators. Animals have evolved to use camouflage, stotting, and warning tactics to escape becoming dinner. And as a last result, there’s always fleeing.

Many animals often have multiple predators, and scientists are aware that prey use different methods to flee from each type of predator. “However, the more subtle multi-predator escape strategy, of a prey varying its escape trajectories in response to different predators, has yet to be described,” according to an article published this week in the journal PLoS ONE. Sounds like a good reason to study it, doesn’t it?

Sure enough, that’s just what the authors of the article—scientists from the Smithsonian Tropical Research Institute in Panama—did, using túngara frogs as their subject. Túngara frogs are “palatable anurans [from ancient Greek for ‘without a tail’],” the team writes, eaten by many Central American animals including bats, snakes, opossums, bullfrogs, cane toads, and even large crabs and spiders. So how do they escape so many hungry predators?

The scientists studied two routes predators take to get to the frogs: aerial and terrestrial. A model bat on a zip line represented the aerial predator, and a rubber snake dragged by a monofilament line served as the ground predator. Both model predators were deployed only while male frogs were actively calling in their natural environments, a behavior that makes them more vulnerable to attack.

Not surprisingly, the frogs fled away from the snake models. But, in stark contrast, the frogs moved toward the bat models, in a move the researchers suspect effectively undercuts the bat’s flight path. “Our results reveal that prey escape trajectories reflect the specificity of their predators’ attacks,” the team writes. “Predator-specific responses like the ones found here are potentially widespread among prey and have been missed due to the subtlety of altering a flight path.”

Go frogs, go!

Image: Brian Gratwicke