Bats change their ear shapes to hear better

Bats have the ability to alter their outer ear shapes considerably to make their hearing more flexible, a new study has suggested.

The flying mammals most well known for their abilities to navigate and pursue their prey in complete darkness.

By emitting ultrasonic pulses and listing to the returning echoes, the animals are able to obtain detailed information on their surroundings.

Acting as biosonar receiving antennas, the ears of bats perform a critical function in bringing about these ultrasonic sensing capabilities.

“Certain bats can deform the shapes of their ears in a way that changes the animal’s ultrasonic hearing pattern,” said Rolf Muller, associate professor of mechanical engineering at Virginia Tech.

“Within just one tenth of a second, these bats are able to change their outer ear shapes from one extreme configuration to another.”

“In about 100 milliseconds, this type of bat can alter his ear shape significantly in ways that would suit different acoustic sensing tasks.”

Muller said that as a consequence of these shape changes, the shape of the animals’ spatial hearing sensitivity also undergoes a qualitative change.

Using a combination of methods that included high-speed stereovision and high-resolution tomography, the researchers from Virginia Tech and Shandong University reconstructed the three-dimensional geometries of the outer ears from live horseshoe bats as they deformed in these short time intervals.

Using computer analysis of the deforming shapes, the researchers found that the ultrasonic hearing spotlights associated with the different ear configurations could suit different hearing tasks performed by the animals.

The paper will be published in Physical Review Letters, a prestigious peer-reviewed journal of the American Physical Society.

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