March 29, 2014
Unique Call Allows Male Bats To Lay Claim On Insect Prey
redOrbit Staff & Wire Reports - Your Universe Online
While experts have long known that bats use ultrasonic calls to locate insect prey, research published earlier this week reveals that males have a second distinctive set that essentially allows them to call dibs on a potential meal.
The new study, which appears in Thursday’s edition of the journal Current Biology, explained that there is a correlation between these special sounds and changes in the flight behavior of other bats. The authors believe that the call tells other male big brown bats to back off, laying claim to the prey and increasing the chances of a meal for the calling bat.
“Despite decades of study, many things about common bat behaviors such as foraging remain mysterious,” said lead author Genevieve Wright of the University of Maryland Department of Biology. “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.”
Wright and her colleagues discovered that the male big brown bats produce a special sound known as a frequency-modulated bout (FMB) that advises other bats with whom they are foraging to stay away from their prey. They discovered the FMB while analyzing audio recordings [.MOV] of two bats that were foraging together.
During their examination of those recordings, the five-person University of Maryland team noticed calls that differed from typical echolocation. Those observations led them to analyze video and audio recordings of the creatures’ calls and flight paths as male and female big brown bats flew solo or in pairs while hunting tethered mealworms.
Their analysis revealed sequences of three to four calls – calls that were lower in frequency and longer in duration than normal echolocation pulses. This special call serves as a unique identifier for the bat emitting it, but for reasons not yet currently known to the study authors, it is only the male big brown bats that emit the call.
“When two males flew together in a trial, it was not uncommon for each bat to emit FMBs. We found that the bat emitting the greatest number of FMBs was more likely to capture the mealworm,” Wright said, noting that unlike other animal calls that are meant to attract fellow hunters to a food source, the FMB is meant to repel other bats.
In fact, the researchers found that the males emitting the sounds were more likely to attack the mealworm, while its fellow foragers typically moved further away from the food source. Furthermore, based on the unique features of the call, they were able to trace them back to the specific male that made them 96 percent of the time.
“Despite decades of study, many things about common bat behaviors such as foraging remain mysterious,” added 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.”