Big Brown Bats Call Dibs On Their Dinners

You probably can't tell, but there's quite a bit of bat chatter going on in the American night sky. We knew that bats use echolocation to find food, but researchers have recently realized that they also have a variety of social calls. At ScienceNews, Scicurious reports on new research that describes one function of that social communication: to keep others away from a tasty snack.

"A big brown bat is not the leathery monster you might picture," she writes. To start with, they're not actually all that big. "About 10 centimeters (four inches) long and weighing a bit less than a fun-size Snickers, these bats have a wingspan of about 30 centimeters (one foot)."

The problem with understanding the social dynamics of bats is that most research has been done on wild bat colonies, which can't be subject to tightly controlled laboratory experiments. So University of Maryland graduate student Genevieve Spanjer Wright turned to nuisance bats; animals that had been captured after panicked homeowners called animal control to report bats in their attics.

Wright and her colleagues released pairs of big brown bats (Eptesicus fuscus) into an arena with a mealworm tethered to the floor.

The two-bats-one-bait scenario produced a competitive situation. It was also a tough task, as bats aren't used to attacking a tethered meal. Bats exposed to the arena for the first time flew hungrily and helplessly — and silently.

But when bats had been trained to pick up the tethered mealworm, the situation changed. In results published March 27 in Current Biology, Wright and her colleagues showed that experienced bats began to emit a series of calls called frequency-modulated bouts, or FMBs, three to four pulses followed by a "feeding buzz." These were longer and lower in frequency than the pulses that big brown bats use for echolocation. The sounds were highly individual, and the scientists were easily able to trace them to a particular bat.

It was usually the most social bat that gobbled up the worm, by using their calls to drive their competitor away. What's interesting is that this pattern only emerged for pairs of male bats, not females.

Because female bats are more likely to associate together and forage near each other, Wright suggests that they might behave in a more cooperative manner. But scientists still need to figure out whether this always holds true. "The piece that's missing is that there will be female bats flying around with the males," [James Simmons, a neuroscientist at Brown University] explains. "What do female bats do when other bats are around?"

The study provides a unique glimpse into the social lives of a group of fascinating, misunderstood animals.

Head on over to ScienceNews to read Scicurious's entire article: Bats' dinner conversation may go over your head.

Image: Big brown bat via Flickr/Angell Williams.