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August 04, 2014

Costa Rican bats use natural hearing aids

Leaves rolled-up as ‘ear trumpets’ used by bats to amplify sound, a study shows.

Costa Rican bats use natural hearing aids

The Costa Rican Spix disc-winged bat is a tiny creature that lives in dark environments like caves, where it is nearly impossible to see. The bats therefore rely heavily on their sense of hearing and use a natural hearing aid to help them hear.

The researchers discovered that the Spix disc-winged bat uses rolled-up leaves in order to communicate and pinpoint other bats. The study involved the recording of 79 one-note ‘inquiry’ calls from flying bats and 65 ‘response’ calls from roosting bats consisting of 20-25 sounds. Both types of call became as much as 10 dB louder due to the furled leaves.

The discovery provides further insight into the hidden intelligence of animals.

Ear trumpets

The Spix disc-winged bat, named for the unique disks on its thumbs and feet, makes and receives calls to maintain in contact with other bats, ensuring that group members do not become separated.

The tapered, unfurled leaves are used as acoustic horns. By compressing sound down in the tapered tubes, the sound is amplified in the same way an ear trumpet amplifies sound.

About the study

The study was carried out by researchers Gloria Chaverri and Erin Gilliam from Universidad de Costa Rica and North Dakota University and published in the scientific journal ‘Behavioral Ecology’.

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