Bat babies also babble

The vocalizations of young sac-winged bats are shaped by the same features that characterize human babbling. (Image: Michael Stifter & Ahana Fernandez)

“Mamama”, “dadada” …: The typical babbling in the context of language development in toddlers has an astonishing parallel in the animal kingdom, shows a study: the juveniles of sack-winged bats practice communication sounds in a similar way to human children, acoustic analyzes show. The findings thus shed light on the basic principles and evolutionary origins of highly developed forms of communication, say the researchers.

Being able to convey complex information to our fellow human beings is a key element of our success. In order to master the tricky language system, however, a lot of learning and training is necessary. Children must first listen carefully to caregivers in order to be able to imitate the sounds afterwards. Parents help their children intuitively through so-called baby language: the high pitch of the voice and slow, clear pronunciation encourages attention and children can recognize sound patterns better.

In order to play back, they must then be able to precisely control their vocal apparatus. To do this, every toddler has to train the complex movements of the tongue, lips and jaw. This is exactly what is reflected in the babbling. Above all, the production of the so-called canonical syllables such as “da”, “ba”, “ga” is practiced. The Babbel phase has universal key features – regardless of cultural influences and the respective language.

Listening to bats

Baby language and babbling characterize only the complex language development in humans, one might think. But in an earlier study, the researchers led by Mirjam Knörnschild from the Smithsonian Tropical Research Institute in Panama City were able to show that there are parallels in a particularly communicative bat species from Central America. According to this, the females of the sack-winged bat (Saccopteryx bilineata) change the sound of their vocalizations, depending on whether they are aimed at young animals or adults. In addition to this similarity to human baby language, the scientists also found indications of special sound patterns in the young animals. They have now devoted a more detailed analysis to this phenomenon.

To this end, the researchers eavesdropped on young sack-winged bats in their natural habitat in Panama and Costa Rica: They made daily acoustic recordings and videos of the little ones – from birth to weaning. The scientists were initially able to clearly document the conspicuous vocalization behavior of the young animals: “The individual sequences can last up to 43 minutes and are characterized by long, multi-syllable sequences that contain syllable types from the adult vocal repertoire and can still be heard at a considerable distance from the day quarters are “, reports co-author Martina Nagy from the Museum für Naturkunde in Berlin.

Characteristic Babbel features

In order to work out the characteristics of the babbling more precisely, the scientists then analyzed the recordings with acoustic evaluation programs. In this way they were finally able to make it clear: The vocalizations of young sack-winged bats are shaped by the same features that characterize human babbling. “They are, for example, also characterized by the repetition of syllables – similar to the characteristic syllable repetition – ‘dadada’ – in human babbling,” says co-author Lara Burchardt. In addition, the vocalizations of the bat juveniles are rhythmic and occur in all male and female bat juveniles, the analyzes showed.

As the researchers explain, Babbel-like behavior was already known in young songbirds as part of the learning of vocalizations. However, the bats are now mammals. Songbirds have special sound devices and a different brain structure than mammals, so that comparisons with observations in humans are only possible to a limited extent. “It is fascinating to find such clear parallels between the vocal training behavior of two vocal-learning mammals,” says Knörnschild. “Our study thus makes an important contribution to biolinguistics, an interdisciplinary research area that focuses on the biological foundations of human language in order to investigate its evolution,” says the scientist.

Source: Museums für Naturkunde Berlin, Smithsonian Tropical Research Institute, specialist article: Science, doi: 10.1126 / science.abf9279

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