Baby seals may be the latest animal to have a similar trait to humans – raising their voice so they are better understood.
A new study published Monday in the journal Philosophical Transactions of The Royal Society B. found the adorable creatures possess the rare ability of altering their tone.
Only a few species may be capable of changing the pitch of their voice to sound higher or lower, which is a crucial element of human speech.
“By looking at one of the few other mammals who may be capable of learning sounds, we can better understand how we, humans, acquire speech, and ultimately why we are such chatty animals,” explains MPI’s Andrea Ravignani, senior investigator of the study.
Wadden Sea noises
In the study, eight harbor seal pups, aged 1 to 3 weeks old, were held in a Dutch rehabilitation center where researchers checked for vocal plasticity – when an animal or person adapts their voice to changes in the environment.
Vocal plasticity is important to increase potential mating opportunities, escaping predators and the speed of social learning, the study said. Seals are among the few mammals capable of vocal learning.
The baby seals were played sounds from the Wadden Sea for several days at three different volumes ranging from no sound to 65 decibels – about the volume of laughter.
When the seal pups heard louder sea noises, they lowered their tone of voice. The pups also kept a more steady pitch with the more intense noise levels. One seal clearly showed the so-called Lombard effect, producing louder calls when the noise got louder.
The Lombard effect is typical for human speech, as people raise their voices in noise to be better understood. The pups did not produce more or longer calls when they heard different levels of sea noise.
Direct neural connections
Apparently, young seals adapt to the noises in their environment by lowering the tone of their voice, an ability they seem to share with humans and bats. Other animals in similar experiments only raise their voice (i.e. make louder calls) in response to louder noise.
“Seal pups have a more advanced control over their vocalisations than assumed up until now,” says Ravignani.
“This control seems to be already present at only few weeks of age. This is astonishing, as few other mammals seem capable of that. To date, humans seem to be the only mammals with direct neural connections between the cortex (‘the outer layer of the brain’) and the larynx (‘what we use to produce tone of voice’),” he concludes.
These results show that seals may be the most promising species to find these direct connections, and unravel the mystery of speech.