Egyptian fruit bats point sonar beams on either side of a target, not directly at it
According to researchers at the University of Maryland, Egyptian fruit bats, unlike their American relative the big brown bat, locate objects through a series of tongue clicks directed to either side of their target.
Big brown bats locate their fast moving prey—such as mosquitos—by firing sounds from their vocal cords directly at their target. Egyptian bats, on the other hand, fire their sonar beams to either side of the target and automatically calculate the slope. In other words, they find the target’s position through the difference between each sonar beam.
In the study published in this week’s Science magazine, researchers in Israel trained the fruit bats to land on a spherical target relying exclusively on echolocation. Echolocation, like sonar, is the process bats use to navigate through the air and target objects.
At the UMD lab, high speed infrared cameras recorded the bats movement in flight while the shape and direction of their sonar beam patterns was measured with 20 microphones positioned around the room. The above video shows a slow-motion recording of the bat’s echolocation technique.
The scientists say, however, that the fruit bat is sacrificing target-detection for target accuracy: by emitting two sonar beams at a time, the bat is less likely to locate the target altogether.
Cynthia Moss, a co-author of the study and researcher at the University of Maryland’s Auditory Neuroethology Lab, says in a press release:
“We think that this tradeoff between detecting an object and determining its location is fundamental to any process that involves tracking an object whether done by a bat, a dog or a human, and whether accomplished through hearing, smell or sight.”
Yossi Yovel, Ben Falk, Cynthia F. Moss, Nachum Ulanovsky (2010). Optimal Localization by Pointing Off Axis Science