Hunting Bats and a 'Bag of Chips'

It seems there is indeed strength in numbers. When bats hunt at night, they rely on the sounds of their fellow flutterers to find their way to a meal, a behavior scientists like to call the "bag of chips effect," a new study says.

"When you sit in a dark cinema theater and someone opens a bag of chips, everyone in the theater knows that someone is eating chips and approximately where that someone is," researcher Yossi Yovel of Tel Aviv University explained in a press release. "Bats work similarly."

When hunting alone, a bat can only detect insect prey within 10 meters (33 feet), but in a large group they can eavesdrop on other bats and hear a meal 10 times farther away - 100 meters (328 feet).

It's no secret that nocturnal bats use sonar to get around at night, so researchers fitted bats (Rhinopoma microphyllum) with tiny GPS-tracking, ultrasonic recorders to get a better sense of their directional abilities. Specifically, when they were hunting winged ant queens, insects that tend to be spread out and hard to find.

"This allowed us to tap into the bats' sensory acquisition of the world by recording them," Yovel said. "I can look at their sonar recordings and infer when the bats are attacking prey or where they are interacting with another bat."

In the end, Yovel and his colleagues captured more than 1,100 interactions between tagged bats and their peers, suggesting that these flying mammals need some help when hunting. However, there is a limit to this eavesdropping strategy. It's most effective in groups of an intermediate size, whereas too large groups mean bats will only get in each other's way.

The study findings were published in the journal Current Biology.

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