Bat Love Songs Decoded
Aug. 25, 2009
AUSTIN, Texas — It might not sound like crooners singing about love on the radio, but bats sing love songs to each other too, say researchers at The University of Texas at Austin and Texas A&M University who are believed to be the first to decode the mysterious sounds made by the winged creatures.
Their work was published this week in the journal PloS One.
Neurobiologist George Pollak at The University of Texas at Austin, biologists Kirsten Bohn and Mike Smotherman at Texas A&M, and Barbara Schmidt-French of Bat Conservation International in Austin spent three years analyzing thousands of Mexican free-tailed (also known as Brazilian free-tailed) bat recordings to understand their meaning.
They determined that male bats sing songs with distinguishable syllables and phrases to attract females, and in some cases, to warn other males to stay away.
"I am amazed at the richness of the vocal repertoire that bats use for social communication," says Pollak. "Their courtship songs are perhaps the most surprising, since each song is complex and structured."
The bats use several types of unique syllables, or sounds, and they combine these syllables in specific ways to make three types of phrases—a chirp, a buzz or a trill. The males use different combinations of the three during the mating process.
"The sounds they make are very difficult for the human ear to pick up," explains Bohn, the lead researcher of the project. "It's at a very high frequency range, but our recording equipment could track it very well.
"The sounds are made in a specific, arranged pattern to form a song, and there are actually organized sequences within each phrase. They are made to attract and lure in nearby females."
The researchers recorded bats from Austin, where more than one million Mexican free-tailed bats live downtown beneath Ann Richards Bridge, and Kyle Field in College Station, where an estimated 100,000 to 250,000 bats are believed to be winging their way around the football stadium and athletic complex.
"We compared the recordings made by bats in Austin to those at Kyle Field, and we discovered they were almost exactly the same," says Bohn. "The bats in both places use the same 'words' in their love phrases."
Bohn says the results are surprising because in general terms, mammals such as bats don't have language rules—the use of specific sequence of phrases and a complex means of communication to others in their species.
"With the possible exception of whales, you normally don't have this type of communication technique," she says. "You see it frequently in birds, but that's about it. We've learned the vocal production of bats is very specific and patterned, and now we have a model not only to study communication similarities in other animals, but also human speech. So we think this is a big first step."
Pollak adds, "Who would have thought that bats could have one of the most sophisticated and rich vocal repertoires for communications of all animals?"
The Mexican free-tailed bat is one of the most common bat species, measuring about four inches in length with a wingspan of about 12 inches. Dark brown in color with rounded ears, the bats are frequently seen in the southwest United States and are also common in Central and South America. They like to roost in dark places such as caves, inside of barns, the corners of buildings and under bridges.
The project was funded by the National Institutes of Health.