Fruit bats raised hearing different pitches of sounds vocalized in keeping with their aural environment as they matured.
Bats are sophisticated communicators. And not just when they’re in vampire form. New research finds that Egyptian fruit bats actually have regional dialects, depending on the bat chatter that surrounds them as they grow up. The study is in the journal PLOS Biology. [Yosef Prat et al., Crowd vocal learning induces vocal dialects in bats: Playback of conspecifics shapes fundamental frequency usage by pups]
Among humans, one person’s howdy is another one’s g’day. Wild populations of bats also display group-specific vocalizations. But how do these vocal characteristics arise? Do they reflect innate, genetic differences or are they learned? And if bat accents are acquired, who are these furry fliers imitating? Their parents? Or their roost-mates?
To find out, Yossi Yovall at Tel Aviv University and his colleagues captured 15 pregnant fruit bats and divided them into three groups, each of which was housed in its own separate box. The mothers gave birth inside these boxes and their babies, called pups, lived there for a full year. During that time, the researchers exposed the pups to a select symphony of bat sounds. Fruit bats in the wild are reared in colonies that contain dozens to thousands of individuals, so they’re used to being surrounded by a cacophony of calls and other vocal communiques.
For one of the boxes, Yovall and his team exposed the young batlings to a selection of squeaks that were biased toward the higher frequencies. Pups in the second box heard lower-pitched peeps. And the third box got a random sampling of fruit bat hits that was heavy on the mid-range frequencies but also included those at either end of the aural spectrum.
“And what we found is that they were influenced by the playback that they heard.”
“So the control group was using a vocal repertoire that was identical to their mothers and identical to fruit bats in the colony here in Israel. But the two manipulated groups were using different dialects...we actually were able to create three different groups of fruit bats with three different dialects in the lab.”
Of course, birds are famous for their songs. Which the males learn from tutors, typically their dads. But Yovall says when it comes to vocal learning, bats march to a different drummer.
“Here we show that even though the pups were with their mothers, they were exposed to their mother’s normal repertoire, they were still influenced by the background vocalizations that they heard. Now this is probably extremely reasonable in the case of bats because bats roost in these caves with many hundreds of individuals…we believe that this process, which we call crowd vocal learning, because you learn from the entire crowd, is relevant for many other animals that live in crowded colonies.”
As the researchers note in their paper, this sort of social learning is sometimes called “culture.” Even if you’re living in a cave.
[The above text is a transcript of this podcast.]
[Bat sounds courtesy of Yossi Yovall, Tel Aviv University]