Bat pups spend a few months of their lives chattering, just like human babies, before they learn to properly “pronounce” the sound repertoire of the adults in their family. This is one of the closest parallels to learning the Homo sapiens language in another mammal, which can provide important data to understand how this ability evolved.
Stuttering bats belong to the species Saccopteryx bilineata. The animals feed on insects and have a wide geographical distribution throughout tropical America, including most of the Brazilian territory (they are only absent in the vicinity in states in the southern region).
However, the study that deciphered the vocal learning of flying mammals looked at 20 offspring from populations of the species found in Costa Rica and Panama. The research was coordinated by Ahana Fernandez and Mirjam Knörnschild from the Museum für Naturkunde in Berlin (the first researcher is of Swiss Ecuadorian origin, the second German).
The couple and their colleagues followed the bats’ entire “early childhood”, which lasts up to ten weeks of life. At this point they already dominate most of the adult repertoire, which consists of 25 different types of “syllables”. (The quotation marks are necessary because bat syllables are defined as one continuous sound followed by a pause, which is different from those in human languages.)
From the seventh to the tenth week of life, puppies spend 30% of their time rehearsing typical adult noises. The “syllables” they send out can be the same as those of larger bats or are protosyllables, that is, undifferentiated sounds that do not exactly imitate any aspect of adult animal vocalizations.
Protosyllables are the most common sounds produced by puppies (39% of their vocalizations) and occur only in animals’ childhood. In addition, they are very variable, which suggests that babies are exploring the possibilities of their vocal apparatus at this stage.
This is already reminiscent of what babies of our species do, but two other characteristics of the bat chatter are even more similar to what you see in human babies. The first is the repetition of “syllables” like the “ba-ba-ba-ba”, “ta-ta-ta-ta” or of course “gu-gu-da-da” of Homo sapiens from the womb.
The other is the repetitive rhythm of these noises, which is also very similar to that of human babies. The researchers suggest that these details correspond to mechanisms that strengthen the nervous system and train the vocal muscles to function with precision.
The work is another indication that chattering is a critical element in language development. There are also indications for hearing-impaired children who learn different sign languages around the world from birth: Before they can speak fluently, they too babble – with their hands.
The same applies to birds, Knörnschild told Folha. “In our opinion, the main difference is that the bats’ babble includes not only the syllables of songs like birds, but also other sounds from the adult repertoire. And bats of both sexes babble. “
In the case of human babies, interaction with their parents is very important in order to stimulate the chatter – it is common for them to speak to the little ones in what some people call “mummy,” a simplified language with exaggerated intonation. What about bats?
“It’s a fascinating question, and in fact we have some data on it that has been collected by and is being analyzed by Ahana. One would expect the same with bat chicks, but we can’t say anything categorically yet. “