How One Frog's Mating Call Could Land Him A Female, Or Attract Predators
You thought the bar scene was tough? For frogs, finding a date can be a matter of life and death, new research on túngara frogs has found.
The study, "Risky Ripples Allow Bats and Frogs to Eavesdrop on a Multisensory Sexual Display," was published in the journal Science on Thursday and suggests, basically, that bats are creepers who listen in on vulnerable male flirtation. Because this kind of frog has balloon-like vocal sacs, its most effective mating call also causes ripples in the water around them. "Ripples in the water made by throat sac expansion in calling túngara frogs signal their presence both to rivals and to predatory bats," the Science editors write.
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Although the bats can hear the frog calls, fringe-lipped bats have the distinct ability to zero in on them even better using echolocation, the study authors found. No live frogs were harmed during the making of this research, according to Smithsonian, whose Tropical Research Institute was involved in the study. Instead, they used plastic frogs that generated artificial ripples. "When they unleashed bats into the experiment, they found that they dove at the frogs next to rippling pools 36.5 percent more often than than the still ones," said the magazine. Dead leaves in the pool, however, muffled the ripples and limited the bats' ability.
Fringe-lipped bats even look for the ripples as a species cue, another study found. Certain ripples mean tastier frogs. And it wasn't just bats that the frogs had to worry about. The ripples were more likely to provoke frog rivals, who were fighting over the same females, to call for a mate more aggressively. Something about the ripples, and not just the auditory call itself, made the rivals intensify their machismo.
So what is a single frog to do? Keeping silent is the best way to stay alive, yet crying out is the only way to reproduce. This is a common dilemma in the natural world, the Science editors said, and it has implications for natural selection.
If a mating call is more likely to attract predation, evolution may favor the individual with the quiter call. But quieter here doesn't matter. "This physical signature of the call itself cannot be modified; thus, it represents a cost-benefit ratio to calling that cannot be shifted through selection pressure from either side," Science writes. The future for the unfortunate túngara frog is uncertain. Physical byproducts, they say, will "create significant complexity" for the frogs' mating signals.
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