for National Geographic News
Bats may seem silent to human ears, but their calls can reach sound pressures greater than those emitted at rock concerts, a new study says.
The mammals use their natural sonar, called echolocation, to find prey by putting out high-pitched sounds and listening for the noise reflections.
The intensity of such sounds, which are beyond the range of human hearing, were extensively studied for the first time as part of the new research.
At close range—some four inches (ten centimeters) from the bat's mouth—bat cries exceeded 140 decibels (dB), which is a measurement of sound pressure.
That's a higher level than has ever been observed from any airborne animal.
A loud rock concert, by comparison, measures 115 to 120 dB—just under the threshold of pain for humans.
(Related: "Vampire Bats Hunt by Sound of Victims' Breath, Study Says" [June 19, 2006].)
Annemarie Surlykke of the University of Southern Denmark and Elisabeth Kalko from the University of Ulm, Germany, used microphones to track 11 species of insect-eating bats in tropical Panama.
The researchers modified a method for capturing whale songs to accurately measure the bats' vocal output and find out exactly where the animals were flying at any given moment.
"Of course you can't see very well at night, and they fly very fast and change directions all the time," Surlykke said.
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