Human communication

Baby seals change their voices to be understood, study finds


According to the study published Monday in the journal Philosophical Transactions of The Royal Society B, a person or animal using this trait is called “vocally plastic” or adjusts their vocal cues in response to overlapping or obscuring environmental changes. their voices. Being able to communicate clearly and accurately is important for mating opportunities, for evading predators, and for social learning, the authors wrote.
Researchers had several reasons for wanting to test the vocal chops of harbor seal pups. The rare ability to mimic new sounds – vocal learning – had previously been seen in adult harbor seals and a few other mammalian species, the authors said. And very few mammals have the ability to change the pitch of their voice to sound higher or lower, which is essential for human communication.
“By examining one of the few other mammals capable of learning sound, we can better understand how we humans acquire speech and ultimately why we are such talkative animals,” said Andrea Ravignani, senior researcher of the study and researcher. head of the research group of the department of comparative bioacoustics at the Max Planck Institute for Psycholinguistics, in a statement.

Pinnipeds – animals such as seals and walruses that belong to the order Pinnipedia – are excellent models of vocal learning because they are closer than other species to humans in terms of evolutionary development and diversification, have wrote the authors.

After recording the sounds of the wind and other ambient noise on a sandbank in the Wadden Sea – located between Denmark, Germany and the Netherlands – the researchers used computer software to filter the audio recorded at a frequency that would overlap the range of formants in baby seals. mother attraction call. The “forming” is a characteristic component of the quality of a speech sound.

The authors then tested eight healthy, unrelated, wild-born harbor seals aged 1 to 3 weeks from the Seal Rehabilitation and Research Center in the Netherlands. This center ultimately releases the seals into the wild.

When the seals heard a speaker play a 45-minute recording of loud, low, or no noise over several days, they spontaneously called. When the puppies heard louder sea noises, they lowered their voices. During more intense noise levels, the puppies used a more stable tone – and one seal raised its voice. This behavior, known as the Lombard effect, is typical of human speech when people speak louder to be more understandable, the authors said.

The seals may have lowered their tone as low-frequency sounds travel farther in windy environments like that projected by recorded audio, said Caroline Casey, a researcher and assistant professor at the University of California, at the Santa Cruz Institute of Marine and Ocean Sciences. science department. Casey independently peer reviewed the study, but was not involved in the research.

“Or (the lower tone) might help retain the identity of the puppies since the fundamental frequency is a characteristic strongly related to the identity and size of this puppy,” she added. In this context, fundamental frequency describes the range of vocal frequencies of an animal based on the speed, size and use of its vocal cords.
Harbor seals have a lifespan of about 25 to 30 years.

The results showed that “seal pups have more advanced control over their vocalizations than previously thought,” Ravignani said in a statement. “This control seems to be already present at only (a) a few weeks of age. It’s amazing, as few other mammals seem capable of this.”

Previously, it was believed that humans were the only mammals to have direct neural connections between the cortex – the outer layer of the brain – and the larynx, which we use to produce vocal sound, he added. “These results show that seals may be the most promising species for finding these direct connections and unraveling the mystery of speech.”

By studying what neural networks or social conditions need to be in place for language to evolve, birds have been the best animals we can compare ourselves to, Casey said. This is because in studies of the environment and vocal learning or plasticity, birds – unlike most mammals – can be captive-bred and naturally mature faster due to their short lifespans.

“However, there are many differences, especially when it comes to sociology and the history of life between humans and birds,” she added. “We are always on the lookout for mammals that would be good models for studying vocal learning.”

There haven’t been a lot of studies on how plastic calls from young animals can be. With “most studies, especially in nature, sometimes you don’t know the age or sex of the animals you are recording, so it’s very difficult to get high quality recordings of animals of different classes of animals. ‘age, “Casey added. . “Being able to watch this in this very young age group is very unique.”

Future research, the authors wrote, could further explore what other factors might be important for the vocal plasticity of harbor seals.


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