By SINDYA N. BHANOO
Fruit bats make a clicking sound with their tongues to help them navigate their way to the fruits they feed on. The clicking produces a fan-shaped sonar beam that bounces off an object and returns an echo to the bat.
Researchers from Israel and the United States found that the bats can widen or shrink the sonar beam they send out, and adjust the distance the beam travels by changing the loudness of their clicks.
That means the bats “can fly around in a really cluttered field” and still efficiently find fruit, said an author of the new study, Cynthia Moss, a cognitive scientist at the University of Maryland.
The study appears in a recent issue of the journal PLoS Biology.
Dr. Moss and her colleagues trained five Egyptian fruit bats to find and land on a plastic sphere that was moved to different places in a dark room. When the researchers filled the room with obstacles, the bats were able to cover three times as much area with each pair of their clicks as they did when there were no obstacles.
They did this by increasing the volume of the clicks, which are emitted in pairs, and by adjusting the width of their sonar beam. The sonar beam is adjusted in the same way humans might change their field of vision to zero in on a person in a crowded room.
Although clicking is unique to fruit bats, other bats may have similar control of their sonar beams, Dr. Moss said.