Low-Frequency Echolocation Enables Bats to use Stealth to Hunt

A new analysis of the Pallas long-tongued bat reveals that when in flight, the mammal does not simply eat insects in passing, but rather uses echolocation to precisely locate its targets and then stealthfully swoops in for the kill.

Researchers from Queen Mary University of London learned that these bats are not the passive eaters they were thought to be by sifting through piles of the bats' excrement, where they noticed something peculiar.

Among the evidence in the guano was the remains of a type of moth that should typically be able to avoid being captured if the bat were to just a happen to fly by. The moths were present in enough waste samples for the researchers to ascertain that it was not just an unfortunate few moths being eaten, but rather they were being targeted.

The researchers then analyzed the frequency of the bat's echolocation calls, where they found an answer to the puzzle of why these moths were being eaten.

"When we compared the bats' echolocation calls to the moths' auditory abilities, we found that the low intensity echolocation calls were not loud enough to trigger the auditory neurons of moths with ears," said Elizabeth Clare from Queen Mary's School of Biological and Chemical Sciences.

"In effect, the echolocation of Pallas's long-tongued bats is too quiet for the moths to hear and allows them to sneak up on their target using a stealth tactic."

The discovery adds to the list of bats that use a form of stealth to hunt. Previously only the European barbastelle bat was known to employ a stealth hunting tactic.

"Our analysis suggests there might be more bats than previously thought that benefit from this stealthy approach that prevents prey from escaping by listening for bats," Clare said.

That the bats use a low echolocation frequency gives credence to the bat's common nickname, the whispering bat.

Clare and her colleagues' research is published in the journal Functional Ecology.