The ability to learn vocalizations from others is believed to be rare among animals, and songbirds are mainly thought to pick up songs from their parents. But a new PLOS Biology study suggests that in young bats, vocalizations and “dialects” are picked up from nest-mates instead, as they listen to and learn from an entire colony.
Yossi Yovel and colleagues exposed bat pups to recorded bat vocalizations where the dialect differed from that of the pups’ mothers. The results suggested that young bats adopt the dialect of the bats around them, rather than that of their mother. To find out more about this research, I interviewed Yovel via email.
Yovel with the bats he studies
Your research group is known as The Bat Lab. What drew you to bats, and what does your lab study?
YY: I started off as a physicist with a great interest in animal behavior. Therefore, when I learned about bats’ ability to sense the world acoustically via echolocation, I was fascinated. Since then I have shifted my focus to study additional aspects of bat behavior, including navigation and social behavior.
Your lab has an in-house fruit bat colony, which can be viewed via your lab’s live webcam. Tell us about them.
YY: Indeed: our unique in-house colony of fruit bats roosts in our facility, where we can monitor them. They are free to forage outdoors in the wild, where we track them with miniature GPS devices. Each bat has a name and the students know their individual “personalities.” In our PLOS Biology study, we used baby bats, or pups, in a different setup so that we had full control over their exposure to audio playbacks and could record all their vocalizations. But once we had finished the study, the pups were released to join our in-house colony.
What led you to study language acquisition and dialects in bats?
YY: Our interest in mammalian vocal communication is driven by the desire to understand the evolution of human language. We know that vocalizations are learnt in humans, but this ability has not been demonstrated in many other mammals. However, I think that the more we study mammalian communication, the more we learn how complex it really is – and I find it easy to imagine that it could have evolved from mammalian communication.
I am also personally very interested in the function of vocal communication in bat social behavior. Bats live in colonies for dozens of years with the same individuals. They can thus form long-term social bonds and I would like to understand how vocal communication supports these bonds.
By exposing bat pups to audio recordings of other bats’ vocalizations, you found that young bats adopt their colony’s specific dialect rather than that of their mother. How does this compare to language acquisition in other animals, such as songbirds?
YY: Yes, a main finding is that bats don’t learn directly from their mothers, but from the entire vocal stimulus they are exposed to. In songbirds, people usually talk about a tutor (the father) and a pupil (the son), but we show that pups adjusted their dialect to that to which they were exposed, even though it differed from the dialect of their mothers. 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. But this is the first time that this form of crowd vocal learning is shown and I believe that it is probably relevant to many other animals that live in crowded colonies.
What part of your study did you find most interesting?
YY: For me, the most significant finding is that bat pups will learn from everything they hear. So even though the pups were listening to their mothers’ “normal” dialect, they were influenced by the background dialect. You could think of a child moving with his parents to another country where a different dialect is spoken. This child will probably speak with a dialect that includes features of both parents and environment.
What are the next steps for your research, and what do you hope your findings might lead to?
YY: There are many possible next steps. One interesting direction would be to examine what influence dialects have on social behavior. Fruit bats roost in the same caves for dozens of years with the same neighbors and we wonder what will happen when a group of “foreigners” enters an established colony. Will they be rejected? Or will they learn the local dialect?
Research Article: Prat Y, Azoulay L, Dor R, Yovel Y (2017) Crowd vocal learning induces vocal dialects in bats: Playback of conspecifics shapes fundamental frequency usage by pups. PLoS Biol 15(10): e2002556. https://doi.org/10.1371/journal.pbio.2002556
Images Credits: Eran Amichai; Yossi Yovel