The Egyptian fruit bat has at least a thousand vocalizations, all of which mean basically the same thing: “Move!”
If you're going to live in a colony of up to 50,000 individuals, bickering and jostling for space is pretty much a given. But the chaos has an additional benefit: It's crucial for a baby bat’s language development, according to research led by Tel Aviv University neuroecologist Yossi Yovel.
That discovery also got him wondering: Are mothers or the collective cacophony of the colony more effective in teaching young bats how to communicate? (See 16 pictures of bats, just in time for Halloween.)
The colony wins out, according to a new study published October 31 in PLOS Biology.
Not only do bat pups learn a "dialect" unique to the colony they're raised in, but the animals can even learn to emulate vocal arrays different from those found in nature.
Think of it like a child of American parents learning to speak with a British accent while being raised in London.
“This is the first time that this form of crowd vocal learning is shown" in any animal, Yovel says. “And I believe that it is probably relevant to many other animals that live in crowded colonies.”
Moms vs. Mobs
To better understand how pups develop their communication skills, the researchers collected over a dozen pregnant Egyptian fruit bats from central Israel and had them give birth in captive environments. Females have one pup at a time, and are solely responsible for childcare. (We busted six myths about bats—for starters, they're not really blind.)
For the next year, the scientists exposed some of the bat pups to recordings from real colonies, while a second group listened to manipulated recordings that included more high-pitch calls than is typical in an Egyptian fruit bat colony. A third group heard recordings with an unusual amount of low-pitch calls.
In each group, the mother bat was allowed to communicate with and nurse her pup like normal. After around three months, when the bats would normally wean in the wild, the mothers were released back to their native habitat.
At six months old, pups from all three groups had begun to communicate in the dialect that matched their recordings. This suggests that the background chatter of the colony is more influential on the pups' communication than their mothers’ calls. (See "'Whispering' Bat Evolved to Trick Prey.")
“This finding is perhaps not surprising when you think of a pup bat that is under its mother's wing in a dark cave, hearing hundreds of individuals around it,” says Yovel.
Yovel’s findings suggest young bats learn differently than birds, which pick up language from their parents, says Alyson Brokaw, a PhD student studying bat communication at Texas A&M University. (Read more about efforts to better bats' reputations.)
“Much of the work on vocal learning has been done with respect to bird song, [in which] a tutor is imitated,” Brokaw says.
“However, this study demonstrates that vocal learning is not necessarily the result of one-on-one interactions, but through exposure to a more general acoustic environment."
Ultimately, learning more about communication in a social animal like the Egyptian fruit bat might yield insights into our own evolution, Yovel notes.
“The more we study mammalian vocal communication," he says, "the more we learn how complex it really is."