Baby seals can modulate the tone of their voice

Have you ever heard of Hoover, the famous talking seal? In the 1980s, he lived at the New England Aquarium in Boston, USA, and entertained visitors with his famous interjections like “Hello” (“hello you”) or even “get out of here” (“get out of here”), which can be heard in the video below (around 6:40). Of course, don’t expect a miracle: it’s not about holding a conversation with a seal. On the other hand, Hoover is a perfect illustration of the ability of these animals to show vocal learning, that is, to emit vocalizations, those sounds produced by the larynx in mammals, and to acquire new sounds by imitation.

This ability must be distinguished from what is called vocal plasticity: the fact that it can modulate the pitch of the voice, that is, make it louder or softer, usually in response to changes in the immediate environment. Absolutely essential for the production of language as we practice it in the human species, this ability is rare in animals, even more so in mammals. It is found among others in certain species of birds as well as in bats.

Precise modulation adapted to the environment of baby seals

a team of Max Planck Institute for Psycholinguistics (Netherlands) was interested in this capacity for vocal plasticity in young seals: at the Pieterburen Seal Center (Netherlands), a care and rehabilitation center that takes in sick, injured or too young seals to handle themselves in the wild, researchers studied eight seal pups. Vitulina Seal less than three weeks.

Young seals were exposed to different natural sound recordings (“essentially the sound of the wind”, according to the researchers) of the Wadden Sea, which extends along the Netherlands. The researchers presented the seals with three sound variations from these recordings. The first was the initial recording, with a sound level of around 25 decibels, the equivalent of a low-voice conversation. The second was slightly amplified, reaching the “normal” intensity of the human voice (45 decibels). The latter was louder, reaching 65 decibels, equivalent to the noise of a busy street or a classroom.

When listening to the sounds emitted by young seals, the researchers observed a real vocal plasticity in response to these different sound environments: the louder the surrounding sound, the lower the vocalizations produced (without being louder or longer) .

Neural connections to study

According to the research team, this indicates a particularly advanced control of seals over the production of their vocalizations, especially at such a young age. To produce sounds, an animal (including the human species) makes voluntary modulations of certain acoustic parameters. In humans, specifically, this control passes through a very specific area of ​​the brain: the laryngeal motor cortex (relating to the larynx, therefore), located in the outer layer of the brain.

The results obtained by the Dutch team suggest that seals would be an interesting species to study to precisely establish the connections between the laryngeal motor cortex and the motor neurons located at the level of the larynx, responsible for the movements of this essential organ for the functioning of the apparatus. phonatory.

Unraveling the mystery of human language

The results of this study published in the journal Philosophical Transactions of the Royal Society B Biological Sciences certainly provide the perfect excuse to watch absolutely adorable videos of baby seals, but they’re also great for human linguistics research. Andrea Ravignani, one of the authors of the study in question, explains that “By studying one of the few other mammals that can learn sounds, we can better understand how we humans developed our ability to speak and, even more broadly, why we are such talkative animals.” Not only would it be possible to learn more about how communication adapts to the environment, but these results constitute a solid path to be explored for the study of the evolution of human language.

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