Bats have dialects

The environment where we grew up molded us in what we are today. People that surrounded us have a dramatic effect also in how we communicate, that’s why if you were born in Wales you speak slowly, if you come from Ireland you talk really fast, if you are Italian you speak also with your hands and if you are Scottish…I am surprised you can even understand yourself, nobody can understand what you are saying! Anyway, my point is, we all have a dialect. Even if we speak the same language we will pronounce the words differently.    

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I’m sure most people think this is a feature exclusive of humans, few more people may know that this also happens in birds and cetaceans and almost nobody knows that the actual list of animals with a dialect is much longer. We can include seals, sea lions, elephants and also bats. 

Today we are going to discuss bats. There was an evolutionary divergence between winged mammalians and our ancestors that dates back tens of millions of years ago. Yet we are not so different.   

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For instance, bats are also social animals, they can form communities of up to millions of individuals at a time and they also form social bonds with each other.   

A recent study showed that bats are capable of vocal learning, which means that they can modify their vocalizations after hearing sounds. A bit like if you moved to a different country right after you were born, you would pick up the new accent. A team of scientists lead by Yossi Yovel, found that bat pups can learn dialects the same way  (Prat et al. 2017).  

Yovel studied the Egyptian fruit bats (Rousettus aegyptiacus), obviously most of what these bats have to say is outside the range of human hearing, but some of their social vocalizations are well within the range, so we can hear them when they socialize. As you know during daytime the bats are crammed into their caves and Yovel noticed that each time bats were bumping into each other they were making an irritable chirp, almost like to say “get out of my way”. 

So what Yovel did was to find 15 pregnant bat mothers and sort them into 3 different captive colonies. Each mother gave birth to a pup. When the pup were grown enough (after two and half months) they were separated from their mothers and Yovel thought it was cool to teach them how to say “get out of my way”, so each day of their life for 1 year, these pups were listening to a recording of this vocalization. The pups were divided in 3 groups and each group was exposed to a vocalization from a different dialect. After one year Yovel found that the pups maintained some of their mother’s dialect but their vocalizations became more similar to the dialect of the recordings (Prat et al. 2017).  

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But how do we know those were different dialects? These vocalizations had basically different frequencies (the pitch).  The lowest pitch was at 250 Hertz and the highest pitch group was at 1,315 Hertz (Prat et al. 2017). So what this study revealed was that bats listen and learn the vocalizations of the whole colony that surrounds them, a sort of “crowd vocal learning”. Most likely, this is to make it easier for bats to recognize their colony mates. Of the 15 pups from the study, one died but the other 14 are now grown adults with thick funny accents. Don’t get on their way! 

Reference:

•   Prat, Yosef, Lindsay Azoulay, Roi Dor, and Yossi Yovel. 2017. “Crowd Vocal Learning Induces Vocal Dialects in Bats: Playback of Conspecifics Shapes Fundamental Frequency Usage by Pups.” PLoS biology 15(10): e2002556. http://www.ncbi.nlm.nih.gov/pubmed/29088225. 

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