Big Brown Bats Make Special Sounds to Warn Rivals, Researchers Find

Big Brown Bats produce a special call sound to warn their rivals, a new study has shown.

The study, conducted by researchers at University of Maryland, found that male brown bats produce another kind of ultrasonic social call, warning the other bats. Researchers have dubbed the special call as "frequency-modulated bout" (FMB).

Eptesicus fuscus, also known as the Big Brown Bat, can be found in regions from Southern Canada to extreme Northern South America and even the West Indies. These bats use echolation to avoid obstacles and hunt prey. In the current study, researchers found that bats also use echolation to fend off potential rivals.

The FMB is a sequence of three or four sounds. These calls have lower frequency, but are longer in duration than the usual echolation sounds produced by the bats. According to the researchers, these sounds are unique to each bat, meaning that it is possible to identify a bat using the FMB that it produces.

In the current study, researchers found that audio recordings of bats foraging together sounded different than when these bats hunted alone. On closer examination, researchers found that male bats were making distinct "back off" calls.

The FMB increased a bat's chances of catching a prey, researchers said.

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

The behavior was found in the males of the species too. According to the researchers, females form close roost connections and often hunt only in familiar locations. The males tend to forage alone or in groups of bachelors.

The study shows that science hasn't fully understood bat behavior.

"Despite decades of study, many things about common bat behaviors such as foraging remain mysterious," said 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."

The research was funded by National Institutes of Health, and by a training grant from the National Institutes on Deafness and other Communication Disorders and is published in the journal Current Biology.

Social communication is important for Big Brown Bats. Other researchers have found that baby brown bats, when separated from their mothers, squeak loudly. These bats can also make audible noises such as hissing.

Another species of bats called False Vampire bat, Megaderma lyra can recognize each other by the kind of sounds that they make, a study had recently reported.