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Bats have superior acoustic perception, but still fly into walls

Bats have such an extraordinary sense of acoustic perception that they can pinpoint something as small as a mosquito using echolocation. They use sound waves to perceive the shape, size, and texture of objects, and to calculate their three-dimensional location. 

Considering that bats have such a superior sense of detecting objects, why do they often collide with walls? A team of scientists at Tel Aviv University (TAU) has found that these collisions do not result from a sensory limitation but rather from an error in acoustic perception.

The TAU researchers released dozens of bats in a corridor blocked by objects of different sizes and made of different materials. The experts were surprised to see that the bats collided with large sponge walls.

“We flew bats down a corridor blocked by objects with different intensity-aperture combinations. To our surprise, bats crashed straight into large walls with weak echo intensity as if they did not exist,” wrote the researchers.

“The echolocation behavior of the bats indicated that they did detect the wall, suggesting that crashing was not a result of limited sensory sensitivity, but of a perceptual deficit.”

The experts referred to the cause of the collisions as acoustic misperception. The team speculates that the misperception occurs due to the unexpected combination of a large object and a weak echo. This disrupts the bats’ sensory perception and causes them to ignore the obstacle, similar to how people run into transparent walls.

The researchers concluded that the bats’ acoustic perception depends on a typical correlation of the dimensions with objects in nature – a large object should produce a strong echo and a small object a weak echo.

“By presenting the bats with objects whose acoustic dimensions are not coherent, we were able to mislead them, creating a misconception that caused them to repeatedly try to fly into a wall even though they had identified it with their sonar,” said Dr. Danilovich. “The experiment gives us a peek into how the world is perceived by these creatures, whose senses are so unique and different from ours.”

The study is published in the journal PNAS.

By Chrissy Sexton, Staff Writer

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