Science & Environment

Bats sabotage rivals' senses with sound in food race

A species of bat can interfere with the sound signals of competitors to "steal" their food.

Image caption Mexican free-tailed bats emit specialised signals which scramble the echolocation of competitors

Bats were "jammed" the moment they were about to home in on their insect prey, making them miss their target.

Media captionListen to the bat's jamming sound

The rival that emitted the call was then able to capture and eat the insect for itself.

This is the first time scientists have witnessed this behaviour in one species - the Mexican free-tailed bat - a team reports in Science journal.

When bats swoop in darkness to catch prey, they emit high-pitched sound waves - a process called echolocation - which speeds up as they get closer to their target. This well-known skill is vital for them to hunt for food and to navigate their environment. This new research shows that others can effectively push them off their tracks mid-hunt.

Lead author of the work, Aaron Corcoran from Wake Forest University in North Carolina, was initially studying moths when he heard these bat calls.

"One bat was trying to capture an insect using its echolocation. The second bat was making another sound that looked to me like it might be trying to jam or disrupt the echolocation of the other bat," said Dr Corcoran.

"Most of the time when another bat was making this jamming call, the bat trying to capture the moth would miss", he added.

In order to study this initial observation further, Dr Corcoran had to illuminate the night sky with a spotlight. On it, he attached a camera with which to record bats capturing insects.

He then reconstructed bats' flight paths to determine their precise position as they emitted sounds. This was done by placing microphones at various locations to measure the time differences between the sounds.

"We can stitch together all of the sounds that each bat makes and produce a map of their flight trajectories," explained Dr Corcoran.

When these recorded sounds were manually played back to the bats as they were about to catch a moth, it sabotaged their hunt in the same way. Other recorded bat sounds had no impact.

Media captionThe first bat captures an insect but the second bat's signal is jammed

The finding was really unexpected, Dr Corcoran told the BBC.

"Nobody has seen anything like this in any other animals which echolocate. It's not necessarily surprising that they're competing with each other [for food] but the fact that they've evolved this jamming signal is quite new.

"When a bat is just about to capture a moth we know they are susceptible to jamming at that point. When we look at it from an acoustics or physics point of view, the jamming sounds are produced at the right time and made at the right frequency that match the frequency the other bats are using."

The researchers will now look to establish whether this skill is unique to this one species, the Mexican free-tailed bat.

Image caption Foraging bats were attracted to this field location with the ultraviolet light tower seen in the right of the image, and the bat sounds were recorded on microphones

Prof Kate Jones at University College London, who was not involved with the study, said that it was fascinating that bats "are doing all kinds of crazy things that we don't know about".

They operate in the world using sonar sound and it takes new technology to access this entirely different world, she added.

"Technology is opening up our understanding of these deeply cryptic creatures," the UCL researcher explained.

Prof Jones, who also studies echolocation in bats, said that there was still much to learn about the social calls bats make, and this new study advanced the field.

Head of monitoring at the Bat Conservation Trust, Dr Kate Barlow, also commented that social interaction between bats was difficult to study because of their small size and nocturnal habits.

"This study reveals another way in which bats have learnt to take advantage of their competitors by listening out for their feeding buzzes... presumably with the intention of then sneaking in and catching [an] insect for themselves. Very sneaky!"

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