Bats Argue Over Food, Sex, and Where They Perch and Sleep

Many vocalizations produced by bats sound the same, but send different messages.

Posted Oct 06, 2019

Listening to bat chitchat tells us a lot about their highly nuanced vocal communication 

Bats are fascinating animals. It's estimated there are at least around 900-1200 species of these amazing mammals and that they make up about one-fifth of Earth's total mammalian population, surpassed only by rodents. Bats typically are highly social and vocal.

I recently learned of an extremely interesting study of one species of highly social, vocal, and long-lived bats called Egyptian fruit bats, which shows that although many of their vocalizations sound the same to us, they're highly nuanced and are used in various sorts of aggressive encounters. It's not surprising that these tightly packed bats quarrel with one another using various sounds.

The research article in which these data are reported was published in Scientific Reports by Yosef Prat, Mor Taub, and Yossi Yovel in an open-access essay titled "Everyday bat vocalizations contain information about emitter, addressee, context, and behavior." The database for this study was very large, consisting of 162,376 vocalizations, along with video recordings of social interactions recorded continuously over 75 days for 22 bats. Data were analyzed for 14,863 vocalizations produced by seven adult females.

The researchers also were able to identify who emitted a vocalization and to whom it was addressed. The research essay is available for free online and all necessary methodological and analytical details can be seen there. Two popular accounts of this research are available in essays called "Bat chat: machine learning algorithms provide translations for bat squeaks" and "Researchers 'Translate' Bat Talk. Turns Out, They Argue—A Lot."

Prat and his colleagues tested for variations among different vocalizations produced in four distinct and common aggressive contexts including "feeding aggression (quarrelling over food), mating aggression (protest of females against males’ mating attempts), perch aggression (face-to-face aggressive display, where the two bats perch in close vicinity), and sleep aggression (squabbling in the sleeping cluster)." They note, "Typically in these interactions, a bat aversively violates the personal space of another bat (e.g., by sniffing it or trying to grab food from its mouth), and the other bat’s reaction would include an acoustic protest."

The results of this study are very interesting and important. Basically, the researchers learned that the nuanced vocalizations of these bats contain "multilayered information," although to humans, they all sound very similar. They also were surprised to learn that these vocalizations that are rich with information have information about the bat to whom they're addressed.

These data are not all that unexpected, given the darkness in which these bats live. I like what the researchers write in their conclusion: Inspired by the behavioral usage of human language, we believe that it is extremely beneficial to delve into the everyday chitchat among animals when attempting to track the route of language evolution. 

Stay tuned for further discussion of the ways in which different nonhumans communicate with one another. Sounds and smells that seem the same to us, clearly are very different to individuals of the species in which they're emitted. Studies such as the one on which I'm reporting clearly show that we need to be more sensitive to the needs of other animals and how they communicate with one another in various environs. 

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