Bats Use Bidirectional Echoloation by Calling Through Their Mouth and Nose

It turns out that a certain bat may actually emit two different types of weak echolocation signals alternately in order to find prey. Scientists have discovered that the barbastelle bat emits one signal upward through the nose and one downward through the mouth to discover prey and keep track of the environment.

Barbastelle bats feed almost exclusively on eared moths by using "stealth echolocation" signals that are 10 to 100 times weaker than those of other aerial hawking bats. These low intensity signals prevent early detection of the bat and can be heard by moths only at short distances. This leaves no time for evasive behavior.

In this latest study, the researchers investigated the two different echolocation signal types that the bats used. More specifically, they determine the source level and sonar beam direction of more than 300 calls of wild bats.

The researchers found that both types of search signals had very low source levels as compared to other aerial hawking bats. In addition, the two signal types were emitted in different directions. Type 1 signals were directed downward and type 2 signals were directed upward. The researchers believe that type 1 signals are emitted through the mouth while type 2 signals are emitted through the nose.

The researchers believe that the "stealth" upward signals might be used for the search and localization of prey. The downward directed signals, in contrast, may come at the cost of reducing the detection range for the environment below the bat.

The findings reveal a bit more about this particular species and how it navigates the nighttime world.

The findings are published in the journal PLOS One.

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