Love Songs Can Be Deadly For Frogs

The dating game can be deadly for some frogs. Túngara male frogs fill the nighttime world at their shallow ponds in Central America with croaky love songs, but their serenades sometimes attract a predator instead of a lover.

Hunting bats pick up on the lusty calls and zero in on dinner, according to research published in Science yesterday. The flying mammals not only hear these tiny amphibians’ songs, but they also detect the ripples created by the noise on the surface of the water.

The Túngara frog’s desire doesn’t necessarily blind him to the threat. When he senses a bat flying overhead—as the frogs often do—he immediately cuts the music. Unfortunately, this doesn’t guarantee his safety. For several seconds after the song has died the ripples created by frog’s vocal sac inflating and deflating continue to spread; the bats sense the movement by echolocation, enabling them to hone in on lover boy.

Lead researcher Wouter Halfwerk of Leiden University first wondered if the ripples gave the frogs away after he learned that other bat species use echolocation to detect fish breaking the surface of water. He and colleagues observed the frogs and bats in the wild and suspected they were on the right track.

They gave the frogs a break when they set out to prove their theory. They put plastic frogs next to shallow pools of water and played a recording of their mating calls.  They generated artificial ripples next to some pools while leaving other undisturbed.  The bats consistently dove more often at the frogs next to the rippling pools.

The love-struck Romeos inadvertently create a bulls-eye on themselves. If only cupid were taking aim, rather than bats.