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article imageHoly hijinks Batman! Bats scramble each other's calls for food

By Megan Hamilton     Nov 9, 2014 in Science
Here's a skill that Batman might wish he had: Scientists have discovered that some bats can mess up each other's chances of snagging a meal. Just think: Batman could put the bad guys on a diet by doing this. He could starve them into behaving.
Batman, however, has nothing on Mexican free-tailed bats, who apparently do this all the time. These bats are known to emit at least 15 types of social calls, Mother Nature Network (MNN) reports. Now a recent study shows that bats are quite clever at using their calls in a nefarious way.
This is little fellow is a Mexican free-tailed bat.
This is little fellow is a Mexican free-tailed bat.
USFWS/Ann Froschauer
When it's dark and bats are hunting bugs, they emit rapid ultrasonic calls that echo back the insect's exact location. Called the "feeding buzz," these sounds are necessary for hunting, but it's also a way of telling their colleagues where the food is. Inevitably, this creates more competition for the food. While it may seem as if the bat initially honing on the prey has the advantage, this isn't so. Nearby bats can actually send out a jamming signal that makes the hunter miss its food, thus allowing the interfering bat to snatch the prey.
The study's lead author, Aaron Corcoran of Wake Forest University in North Carolina, was studying moths when he heard these bat calls, BBC News reports.
"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," Corcoran said.
"Most of the time when another bat was making this jamming call, the bat trying to capture the moth would miss.
Corcoran and his fellow researchers set to work recording bats on video along with using ultrasonic microphones. Then they compared the bats'calls to their flight paths. After making a 3-D reconstruction, the researchers concluded that hunting bats made the feeding buzz, and their competitors do, indeed, make a blocking signal, MNN reported.
When the researchers took the recordings outside, in Arizona and New Mexico, to test how the signals modified the behavior of wild Mexican free-tailed bats, The Weather Channel (TWC) reports.
"When he played the signal right as a bat was about to catch an insect, the bat was up to 85.9 percent less likely to catch its prey," National Geographic reported, per TWC. "If Corcoran didn't play the jamming signal precisely as another bat homed in on an insect, or if he altered the pitch, it had no impact on ability to catch prey."
Corcoran and William Conner, also a biologist at Wake Forest University, now knew that the bats were more competitive than cooperative, and that they readily used the disruptive jamming call.
"They use it at the moment of truth, when the hunter is zeroing in on its prey," Conner said.
"It's a thrilling finding," Mirjam Knörnschild, a bat vocalization expert at the University of Ulm in Germany, per MNN. "Sonar interference has always been an exciting possible explanation ... for the fact that certain bat species are highly vocal, and this elegantly designed study is a convincing demonstration."
How do the blocking signals work?
These signals work by overlapping the initial hunter's near the end of the feeding buzz, creating sound waves that scramble the auditory processing, thus reducing the hunters' ability to track the insect's position using echolocation. There's nothing preventing the hunting bat from turning around and blocking the intruder's feeding buzz. They can keep sabotaging each other's hunt until one of them gives up, MNN reports.
"Nobody has seen anything like this in any other animals which echolocate, Corcoran told the BBC. "It's not necessarily surprising that they're competing with each other, but the fact that they've evolved this jamming signal is quite new."
There's still much to learn about the social calls of bats, but the jamming signal is "cool" Conner says.
"We think engineers are pretty clever when they use a signal to jam sonar and radar. But bats came up with this idea 65 million years earlier."
So, if Batman ever wants to learn how to scupper his enemies, he could do no worse than listening to this.
More about Bats, bats scramble each other's calls, Batman, the bbc, mother nature network
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