What Bats Say

So what exactly DO bats talk about anyway?

Researchers using a machine-learning algorithm investigated vocal signals of Egyptian Fruit Bats (Rousettus aegyptiacus) in their roost. Their findings suggest not only to they communicate with each other but seem to communicate directly with other members of the roost.

The Egyptian Fruit Bat is a highly social mammal that roosts in crowded, tightly-packed colonies. Many animals communicate vocally, but often non-specifically, but researchers at Tel Aviv University recently discovered that when Egyptian Fruit Bats communicate, they aren’t just making high pitched squeals when they gather together in their roosts. Instead, they often have something specific that they want to communicate.

Here is a summary of the article (published online, 22 December 2016) in the journal “Scientific Reports”: Neuroecologist Yossi Yovel and his colleagues recorded sound and video of a group of 22 Egyptian Fruit Bats over a period of 75 days. Using a modified machine-learning algorithm originally designed for recognizing human voices, they fed 15,000 bat calls into the software and then analyzed the corresponding time-stamped video to see if they could match the calls to certain activities.

They found that the bat calls were not random but instead, they were able to classify 60% of the calls into four categories:
1. Arguments about food,
2. Disputes about position within the sleeping cluster,
3. Responses to male bats making unwanted mating advances, and
4. Bat to bat warnings or scolds when one bat gets too close to another.

Even more specific, the researchers found that a bat would make slightly different versions of his/her calls when speaking to different individuals within the group. Only a few species – including humans and dolphins – are known to address individuals rather than making broad communication sounds.

Where is this research headed? Yovel and his team want to investigate whether bats are born knowing this “language” or if they learn it over time while living in their colonies. They also want to find out if the bats use similar communication modes outside/away from the roost using battery-powered recording devices that they will attach to a small sample of bats, which will be released into the wild.

Citation: Prat, Y., M. Taub & Y. Yovel. 2016. Everyday bat vocalizations contain information about emitter, addressee, context, and behavior. Scientific Reports 6, Article number: 39419.

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