Bats Produce Special Warning Calls to Repel Other Foraging Bats From Prey

It is known that bats' echolocation calls keep them from hitting objects in the night. Now a new study says that they also emit a warning call cautioning other foraging bats to keep off their prey.

The finding led by Genevieve Spanjer Wright, Biology Research Associate from the University of Maryland discovered that male big brown bats produce a special call called 'frequency-modulated bout' (FMB) to caution other foraging males to stay away from their prey.

This is the first study to identify and report the special ultrasonic social call.

The study highlights the importance of vocal social communication among nocturnal animals that forage in groups of the same species. The finding was based on audio recordings of two bats that were flying and foraging together. The experts claimed that the calls produced during the hunting activity differed from echolocation calls.

To trace the mystery of these special calls, researchers further analyzed video and audio recordings of the bats' flight paths and calls as they flew alone and foraged in pairs with females for mealworms. This led them to conclude that special warning calls dubbed FMBs keep other baths away from their prey.

The newly identified FMB is an ultrasonic social call unique to a bat that emits it. The call is a sequence of three-four sounds, longer in duration but lesser in frequency when compared to the echolocation calls.

When these FMB ultrasonic social calls are produced, chances of the bat catching its prey are high because the other foraging bats move away from the prey and the caller.

"When two males flew together in a trial, it was not uncommon for each bat to emit FMBs," says Wright. "We found that the bat emitting the greatest number of FMBs was more likely to capture the mealworm."

Unlike other animals that emit calls to attract group members towards the prey, the bats produce the call to push others away.

"Despite decades of study, many things about common bat behaviors such as foraging remain mysterious," says Wright. "We were able to study a social call that is likely occurring thousands of times a night all over North America during the summer months, yet had not been described or studied before now."

Since the calls were produced only by the male bats, researchers assume that the bats could be displaying their dominance over the region. The FMB calls were not produced by females probably because they are closely associated with their male mates and forage near familiar bats only.

The finding was documented in the journal Current Biology.