The Egyptian fruit bat is a highly social mammal roosting in crowded colonies.{credit}Michal Samuni-Blank{/credit}

Bats are extremely social mammals, that live in colonies of thousands and sometimes millions, and they talk or “sing” to each other to communicate. Now, a group of scientists have studied vocalizations by Egyptian fruit bats and they found out that the calls contain information such as the identity of the caller as well as the context of the call.

The study published in Scientific Reports carries an analysis of almost 15,000 vocalizations of 22 Egyptian fruit bats, recorded over 75 days. The analysis paints a picture of some of the social interactions that the animals engage in.

“Bats spend many, up to 40 years, together with the same individuals around them and they live in the dark. All of these suggest that a sophisticated vocal communication might evolve in such animals and this is what we set to examine,” says Yossi Yovel of Tel Aviv University, corresponding author of the study.

The vocalizations the scientists recorded represented the full vocal repertoire the bats used during the experiment. And it turns out the cacophony of sounds that a person hears entering a bat cave is far from just noise, according to Yovel.

Although the calls sounds alike and were previously categorized under one category that boils down to “bat shouting”, the scientists showed it’s not the case.

“The vocalizations we looked at in this study were all categorized in the past as agonistic calls, that is, aggressive vocalizations emitted during fighting,” says Yovel. “We now show that there is information in this chaos. We demonstrate that a third individual listening to a fight between two bats can tell who is shouting, what is the context of shouting, for example fighting over food or over position or over mating, and even to some extent who is being shouted at.”

That said, the communication of the Egyptian bats described therein doesn’t include clearly distinct words, as human communication for instance does, or what linguists often call semantics. “We do not find a ‘word’ that mean ‘hello’ or ‘move’ or ‘eat’ in bat communication. We just show that the spectral content of the vocalizations or their frequencies contain information about the context.”

The scientists elaborates: “You could imagine this as something like this: when a bat shouts at another bat for taking its food, the vocalizations will always be higher in pitch than when they are fighting over a position in the cave. This is what this cannot be defined as language and yet, because we will probably never fully understand animal communication it is important to understand its complexity.”

The next step, which the scientists have already taken, is into learning whether or not these vocalizations are learned by the bats or whether they are born with their vocal repertoire. “Learning new vocalizations is a main factor characterizing human language and it is debated how much other mammals depend on learning to develop their communication,” comments Yovel.