Biology: Young seals deceive with their voices

In mammals, there is a rule that body size and vocal frequency are closely related – the bigger they are, the deeper they are. Experts call it acoustic allometry. But there are exceptions, like young seals. They use their calls to fool other animals by pretending to be bigger or smaller depending on the situation, according to a study now published in the Journal of Experimental Biology.

Animals that violate allometry are divided into two groups. There are those whose pharynx, mouth and nose, the so-called vocal tract, also do not anatomically correspond to the size of the body, which may explain the ability to cheat vocally. Others can learn new sounds without any anatomy.

The ability ceases after separation from the mother

A research team led by Koen de Reus of the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands, has now confirmed that the latter is true for harbor seals: although there are no anatomical explanations for their vocal abilities, they appear to be exceptionally gifted vocal learners, as which the team from the University of Zurich reported in the study.

Seals, pups, mother


Assumption: the brains of seal pups are wired in such a way that neural processes allow them to control the vocal organs and thus, with a little practice, modulate sounds in a targeted manner. For the study, the researchers used 68 bodies of dead young animals, whose size and vocal tract were measured. They then linked this information to the acoustic recordings.

Why young seals learn to vocalize dishonest information is not clear, de Reus said. It is possible that they try to impress their rivals with lower calls and, conversely, try to attract the mother’s attention with higher calls. Interestingly, seals only use their vocal abilities for a short time. After about four weeks, they separate from their mother, become independent – and fall silent except for a few clicks and growls.

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