A new study has revealed that baby seals can alter their voice tone to respond to different sounds, just like humans.

Scientists in the Netherlands made sea noises to baby harbour sealings (Phoca Vitulina) which are found all over Northern Europe. 

The experts discovered that almost all the pups reduced their voice volume when exposed to more intense sounds. 

Experts believe that seals possess ‘vocalplasticity’, which allows them to change the tone of their voice. This is a rare trait among mammals other than humans. 

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Pictured, an adorable harbour seal pup at the Seal Centre Pieterburen, in Pieterburen, the Netherlands. The species (Phoca vitulina) lowered tone of voice when they were played sounds of the sea

Pictured, an adorable harbour seal pup at the Seal Centre Pieterburen, in Pieterburen, the Netherlands. When they were playing sounds of the sea, the species (Phoca Vitulina), lowered their voices.


Pitch is the frequency of a sound. You create pitch when you sing because your vocal chords vibrate at an optimum speed. 

A foghorn emits a low pitch or frequency, whereas a smoke detector emits high pitch or frequency. 

Tone refers a musical or vocal sound that is defined by its pitch, quality, and strength. 

The study was conducted at the Max Planck Institute for Psycholinguistics (MPI) in Nijmegen, the Netherlands, and published in Philosophical Transactions of the Royal Society B Biological Sciences.

Andrea Ravignani, MPI’s senior author, said that mammals other then seals would raise their voice volume as noise levels increased.

‘What seals did was lowering the pitch of their voices to escape the frequency range of noise, something that only animals with good control of their larynx – including humans but potentially excluding most mammals – can do,’ he told CNET.  

“By looking at one other mammal capable of learning sounds, it is possible to better understand how humans acquire speech and why we are so chatty.” 

The team examined eight harbour seal pups, aged between one and three weeks, that were being held at the Dutch Sealcentre Pieterburen rehabilitation centre before being released into the wild. 

The team first recorded noises coming from the nearby Wadden sea to determine if the pups could adapt to the noises around them. 

The pups were then rehearsed the sea sounds for several days in three levels of loudness (ranging between no sound and 65 decibels), with a pitch similar to the pup seals’ calls. 

The team recorded the spontaneous calls of the seal pups to determine if their voices changed to accommodate the sea noises. 

Harbour seals, also known as common seals, live in temperate coastal habitats along the northern coasts of North America, Europe, and Asia

Common seals are also known as harbour seals. They live along the northern coasts in temperate coastal habitats in North America, Europe and Asia.

The team discovered that seal pups who heard louder sea noises lowered their voice pitch. The pups also maintained a more steady pitch when they were exposed to louder noises. 

The pups did no produce longer or more calls when they heard different sea noise levels. 

There was an exception, however; one seal clearly produced louder calls when the noise got louder – something known as the Lombard effect. 

Harbour seals are less abundant in the UK than grey seals. Harbour seals have a dog-like face with large brown eyes, white whiskers and a snub nose

Grey seals are more common in the UK, but harbour seals are much less common. Harbour seals have a doglike face with large brown eyes and white whiskers. They also have a snub nose.


The Lombard effect is a way for people to speak louder in noisy environments.

The Lombard Effect is a characteristic of human speech. It occurs when people raise their voices to be understood better.

It’s a spontaneous response that speakers feel when they hear noise during voice communication.  

Humans display the the Lombard effect too – we speak louder and more clearly in a noisy environment, just like a crowded bar or nightclub.   

The study shows that young seals adjust to noises by changing their voice tone, which is something they seem to share with humans or bats. 

Similar experiments have resulted in other animals only raising their voice (i.e. In response to louder noises, other animals in similar experiments only raise their voice (i.e.

Ravignani stated that Seal pups have a greater control over their vocalisations, than was previously believed. 

“This control seems to be present only a few weeks after birth. This is remarkable, as it is possible in only a few other mammals. 

‘To date, humans are the only mammals to have direct neural connections between cortex (the outer layer in the brain) and larynx (what we use for tone of voice). 

These results indicate that seals are the most likely species to find these connections and solve the mystery of speech.

Seals are also capable of vocal learning – the ability to imitate sounds, just like a parrot does.   

This was previously demonstrated by Hoover, a harbour seal at New England Aquarium in Boston, Massachusetts in the 1970s and 1980s. 

George Swallow of Maine holds Hoover at the animal's home at the New England Aquarium in Boston on August 16, 1971. Hoover was found in June that year by a Maine lobsterman when she was only a day or two old after her mother has been killed. Swallow and his wife took care of the seal and have found it a new home at the aquarium

George Swallow, a Maine lobsterman, holds Hoover at New England Aquarium in Boston’s animal home on August 16, 1971. Hoover was just a few days old when her mother was killed. A Maine lobsterman found her in June 1971. Swallow and his wife looked after Hoover and found a new home for it at the aquarium.

Hoover, the talking seal, was discovered by a Maine lobsterman as a pup in 1971. He was able mimic human speech. 

Hoover was originally kept in a family home. He could speak catchphrases in a gruff New England accent such as “come over here” and “hello there!”  

Harbour seals, also known as common seals, live in temperate coastal habitats along the northern coasts of North America, Europe, and Asia. 

They can be found around the coasts in the UK, including Northern Ireland, Scotland, and Eastern England. 


Grey and harbour seals, also known as common, can be found all year along the coast of Scotland. 

Untrained eyes can find it difficult to tell the difference between grey harbour seals and grey harbour seals. 

When viewed in profile, grey seals have much flatter noses (‘a Roman nose’) than harbour seals, whose faces are more dished (they have relatively distinct foreheads). 

Grey seals’ eyes are situated midway between the nose & the back of your head. Harbour seals’ eyes (and mouths!) are much closer to the nose. 

Grey seals have a double chin, unlike harbour seals. In terms of the overall head shape, an oval drawn around a harbour seal’s head would need to be squashed from top to bottom while one drawn around a grey seal’s head would be squashed from side to side. 

Grey seals are larger than the other two species. Adult greys can reach a length of 5.9 feet to 6.8 feet (1.8m to 2.1m), and adult harbour can reach 4.2 feet to 5.5 feet (1.3m to 1.7m).

There are also differences in the coats pattern or ‘pelage’, of the two species.

Harbour seals are often fairly uniformly seen, while grey seals have more clearly contrasting grey bellies and darker grey backs with larger more irregularly shaped spots. 

Grey seals with males have darker coats that females. However, a seal’s pelage may look different depending on whether it’s wet or dry and when it goes through its annual moult (December-March for grey seals and September-September for harbour seals). 

Read more: Sea Mammal Research Unit – University of St Andrews