"Treefrogs exploits the auditory illusions of eavesdropping predators”



Treefrogs in the forest have found a way to avoid becoming easy prey for predators and parasites. When they emit mating calls, their wingman helps create an elaborate deception that protects these ground-dwelling animals from being attacked by airborne foes.


Researchers at Purdue University have discovered that male treefrogs reduce their attractiveness to predators and parasites by overlapping the sound of their mating calls with those from other males in close proximity.


The treefrogs of this species have an interesting way to protect themselves from being eaten by predators. They use overlapping calls at nearly perfect synchrony with their neighboring trees, fooling any would-be eaters into thinking they're coming right behind you. "The male frogs are essentially tricking the eavesdroppers with this auditory illusion." said doctoral

student Henry Legett. "Humans experience it too, and we call that ‘precedence effect.'"


Research at the Bernal lab focuses on how communication can be used to facilitate or inhibit

predatory interactions. Research into eavesdropping between species has lead them down many different tracks, but ultimately connects back with that original question; could one animal learn what another was thinking?


The male treefrogs’ synchronized calls are an empty illusion to the female frogs, which was surprising. The male frogs have figured out a way to trick these enemies. We thought the females might be more attracted, but it turns out they’re not! The males only fooled themselves with their illusion and won some free meals while doing so - win-win for all involved parties: Frogs get protection from predators that want preyed on both males AND females; Ladies aren't tricked into danger because there actually isn't any competition here at all (not even close!).


The study included experiments using playbacks of recorded calls from speakers and sound traps both in laboratory and field settings at the Smithsonian Tropical Research Institute (STRI) Panama where Bernal is a research associate. Researchers discovered that after an initial male treefrog sends out its mating call other frogs follow suit within milliseconds!


“It’s so fast, it feels like a reflex. There is no way their brains can process the information they receive and respond accordingly in time before hearing what's going on next door."


Bernal and Legett said that the research has stimulated even more questions about how frogs communicate.


"Why do male frogs call first, when it increases their chances of getting eaten?" Legett wonders. "It seems like an incredibly risky game to play - after all they're only trying out new calls and waiting for other males that may or may not show up."


The work was supported by the National Science Foundation, as well as an A. Stanley Rand Fellowship from Smithsonian Tropical Research Institute and Purdue University to support Legett's research.