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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. (Photo of George Pollak and a Mexican free-tailed bat; Credit: Marsha Miller) 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.>>
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