Bats Use "Love Songs," Foul Smells to Woo Mates

August 28, 2009

In the musical city of Austin, Texas, a group of smelly, pug-faced crooners is hoping to woo some females with surprisingly complex tunes.

That's the finding of a new study of Brazilian free-tailed bats, which now join songbirds and whales as some of the only animals known to use a kind of musical language during courtship.

(Related: "BALD BIRD PICTURE: New Songbird Sports Wispy 'Mohawk.'")

Also known as the Mexican free-tailed bat, the species is quite numerous in Austin and around the Texas A&M University football stadium in College Station.

Based on recordings of the animals from both locations, the researchers found that the bats' songs contain definite phrases made up of birdlike chirps, buzzes, and trills.

(Related: Listen to the different calls of tropical bats.)

Males sing their ballads as they hang upside down or sideways, sometimes flapping their wings and dripping a foul-smelling liquid that further attracts females.

"It's quite a display," said lead study author Kirsten Bohn, a postdoctoral fellow in biology at Texas A&M.

Bat "Jazz"

Normally the bats' love songs sound like a rapid buzzing to humans, because most of the sounds are too high-pitched for us to detect.

But when the researchers slowed down the songs, they could hear phrases made up of specific syllables, which were themselves products of different combinations of notes. (Listen to a sample of a free-tailed bat's song [downloadable .wav file], slowed down eight times to be audible to humans.)

This hierarchical structure in the bat songs distinguishes them from the repetitive noises of most other mammals, Bohn said.

The team also found evidence for higher levels of organization in the bats' songs. For example, songs almost always began with chirps and usually ended with buzzes.

The bats didn't just copy each other's songs, either.

Like gifted jazz musicians, the animals spontaneously combined and varied the lengths of phrases to create songs that were distinct from those of their neighbors and that varied with each performance.

"I actually almost expected each bat to have a combination that it liked," Bohn said. "But instead all of the bats did all sorts of combinations."

Findings published online August 25 in the journal PLoS ONE.

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