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Singing seals open new research avenues

Singing seals open new research avenues
08 Jul
2019
Could grey seals singing Twinkle Twinkle Little Star help develop a new system for studying speech disorders?

New research has found that grey seals can replicate human speech and songs. The study carried out by Dr Amanda Stansbury and Professor Vincent Janik, of the Scottish Oceans Institute (SOI) at the University of St Andrews, revealed that grey seals use the same sound production mechanisms as humans due to having similar vocal tracts. The findings were published in Current Biology and state that the study of seals could be hugely beneficial in providing new insights into the wider study of speech disorders.

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Three young grey seals – Zola, Gandalf and Janice – were monitored from birth by Stansbury and Janik to determine their natural repertoire. Once this process was complete, the researchers began teaching the seals to mimic common seal sounds or noises a seal might normally hear from a herd mate in the wild. Fish was used as an incentive to encourage the seals to come out of the water voluntarily and sing a series of notes. Stansbury would record the seal’s own sounds and play them back. The seals quickly learnt that if they sung back the same note they would be rewarded with fish.

Once the seals were familiar with this process and could easily copy these basic sounds, Stansbury and Janik used a computer to slightly alter them by using higher and longer tones, unfamiliar frequencies and sequences that incorporated vowels from human speech. The seals were then rewarded for matching these new sounds. Stansbury even used some combinations to mimic common jingles and songs that no seal would be expected to produce under natural circumstances. Zola had a particular knack for copying melodies that were played to her, copying up to ten notes of songs such as Twinkle Twinkle Little Star and the Star Wars theme. Gandalf and Janice were more adept at accurately reproducing combinations of human vowel sounds.

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While their renditions were not perfect, Stansbury, who now works at El Paso Zoo in Texas, said: ‘I was amazed how well the seals copied the model sounds we played to them. Copies were not perfect but given that these are not typical seal sounds it is pretty impressive. Our study really demonstrates how flexible seal vocalisations are. Previous studies just provided anecdotal evidence for this.’

It is fascinating that seals have the capability to produce vowel sounds because in general, it is very unusual for animals to possess vocal capabilities flexible enough to expand in this way. This flexibility is something that non-human primates struggle with. ‘Seals are the closest non-human analog we’ve found this behaviour in,’ Stansbury said. This is because seals have a key anatomical advantage: a larynx, or voice box – much like the one found in humans. A larynx is crucial to providing more control when producing sound. Janik added, ‘Surprisingly, non-human primates have very limited abilities in this domain. Finding other mammals that use their vocal tract in the same way as us to modify sounds informs us how vocal skills are influenced by genetics and learning.’

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After one year of working with the researchers, the seal pups were released back into the wild. While there was no conclusive explanation as to why seals have this exceptional ability to reproduce human sounds, the seals’ ability to copy new sounds by changing their formants – the parts of human speech sounds that encode most of the information that we convey to each other – has helped researchers to understand how human language develops. ‘This study gives us a better understanding of the evolution of vocal learning, a skill that is crucial for human language development.’ With this knowledge, Janik believes it ‘can ultimately help to develop new methods to study speech disorders.’

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