Egyptian fruit bats find target by not aiming directly at it

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Washington, Feb 5 (ANI): In a new research, scientists at the University of Maryland have found that Egyptian fruit bats find a target by not aiming their guiding sonar directly at it, but alternately pointing the sound beam to either side of the target.

The new findings, by researchers from Maryland and the Weizmann Institute of Science in Israel, suggest that this strategy optimizes the bats' ability to pinpoint the location of a target, but also makes it harder for them to detect a target in the first place.

For the research, the team of researchers trained fruit bats to land on a spherical target while relying exclusively on their sonar.

Trained in Israel, the bats were then brought to Maryland to be studied in Moss's specialized lab.

High-speed infrared cameras recorded the bats movement in flight while the shape and direction of their sonar beam patterns was measured with a sensitive arrangement of 20 microphones positioned around the large room.

These bats emit paired clicking sounds and the researchers found that the sonar beam created by each click alternated to the left and right of a target.

This alternating pattern effectively directed the inside edge, or maximum slope, of each sonar beam onto the target.

As a result, any change in the relative position of the target to the bat reflected that large sonar edge back at the bat, delivering the largest possible change in echo intensity.

However, less sound is reflected back to the bat from the object than if the sound beam were aimed more directly toward the object.

Thus, the fruit bat's strategy of using the steepest edge of a sonar beam (which intuitively follows a mathematical optimization formula) sacrifices a little target-detection for pinpoint accuracy in tracking.

By changing the conditions of their experiments in the bat lab, the researchers were able to show that the fruit bats will sometimes change their echolocation strategy based on the situation.

To do this, a reflecting board was positioned behind the target, creating "noise" echoes that competed with those from the target, potentially making detection of the target more difficult.

In trials under these conditions, some bats altered their sound beam directional strategy.

These bats started off with the wide side to side pointing that maximizes determining location, but once they got closer, switched to point the beams from both clicks almost directly at the target. (ANI)

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