Bat puppies spend a few months of their life babbling, just like human babies, before learning to correctly “pronounce” the sound repertoire of the adults in their family. This is one of the closest parallels with learning Homo sapiens speech in another mammal, which may provide important data to understand how this faculty evolved.
The babbling bats belong to the species Saccopteryx bilineata. The animals feed on insects and have a wide geographic distribution throughout tropical America, including most of the Brazilian territory (around here, they only do not occur in states in the southern region).
However, in the study that deciphered the vocal learning of flying mammals, 20 offspring from populations of the species that live in Costa Rica and Panama were studied. The research was coordinated by Ahana Fernandez and Mirjam Knörnschild, from the Museum of Natural History in Berlin (the first researcher is Swiss of Ecuadorian origin, the second is German).
The pair and their colleagues followed the entire “early childhood” of bats, which goes up to ten weeks of life. At this point, they already dominate most of the adult repertoire, which is 25 different types of “syllables”. (The quotation marks are necessary because bat syllables are defined as a continuous sound followed by an interval of silence, which differs from those in human languages.)
From the seventh to the tenth week of life, puppies spend 30% of their time rehearsing typical adult sounds. The “syllables” they emit can be the same as those of larger bats or are protosyllables, that is, undifferentiated sounds that do not exactly imitate any aspect of the vocalizations of grown animals.
Protosyllables are the most frequent sounds produced by puppies (39% of their vocalizations) and are only present in the animals’ infancy. Furthermore, they are highly 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 bat babble are even more similar to what you see in human babies. The first is the repetition of “syllables”, such as the “ba-ba-ba-ba”, “ta-ta-ta-ta” or, of course, “gu-gu-da-da” of Homo sapiens from lap.
The other is the repetitive rhythm of these sounds, also very similar to that of human babies. The researchers propose that these details correspond to mechanisms that reinforce the nervous system, training the vocal muscles to function with precision.
The work is yet another indication that the act of babbling is a crucial element for the development of speech. There are hints of this even among hearing-impaired children who learn different sign languages around the world from birth: before they become fluent, they too babble – with their hands.
And something similar goes for birds too, Knörnschild told Folha. “In our opinion, the main difference is that the babble of bats covers not only the syllables of songs, as in the case of birds, but also other sounds in the adult repertoire. And bats of both sexes babble.”
In the case of human babies, the interaction with the parents is very important to stimulate the babbles – it is common for them to talk to the little ones using what some people call “mommyese”, a simplified language with exaggerated intonation. What about bats?
“It’s a fascinating question and, in fact, we have some data about it, which was collected by Ahana and is being analyzed by her. One would expect the same to happen in the case of bat chicks, but we still can’t say anything categorically.”