Baby seals can change their tone of voice

Date:
November 2, 2021
Source:
Max Planck Institute for Psycholinguistics
Summary:
Hoover the 'talking seal' famously imitated human speech. But can
baby seals already adapt their voices to sounds? Researchers have
now studied seal pups only a few weeks old. The pups lowered the
pitch of their voice when they heard louder noises. This vocal
flexibility makes seals an excellent animal model for studying
the evolution of human speech.



FULL STORY ========================================================================== Hoover the seal was initially kept in a family home and could imitate
human speech, barking catch phrases in a gruff accent ("Come over
here"). But vocal learning -- the ability to imitate sounds -- is a rare
trait among mammals.

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. Are seal pups already
capable of changing the pitch (or 'tone height') of their voices?

========================================================================== Wadden Sea noises The researchers studied eight harbour seal pups --
1 to 3 weeks old -- that were being held in a rehabilitation centre
(the Dutch Sealcentre Pieterburen) before being released back into the
wild. To investigate whether the pups could adapt their voices to noises
in the environment, the team first recorded noises from the nearby Wadden
Sea. For several days, the sea noises were then played back to the pups,
in three degrees of loudness (varying from no sound to 65 decibel), but
with a similar tone height to that of the seal pups' calls. The team also recorded the pups' spontaneous calls. Would the pups change their tone
of voice to adapt to the sea noises? 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." ========================================================================== Story Source: Materials provided by
Max_Planck_Institute_for_Psycholinguistics. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Laura Torres Borda, Yannick Jadoul, Heikki Rasilo, Anna Salazar
Casals,
Andrea Ravignani. Vocal plasticity in harbour seal
pups. Philosophical Transactions of the Royal Society B: Biological
Sciences, 2021; 376 (1840) DOI: 10.1098/rstb.2020.0456 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211102093509.htm

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