Mysterious whales, also called right whales, sing using a unique system in their larynx that works on a similar principle to that of land mammals like humans, and was described for the first time in a study conducted on Wednesday.
By returning to the water about fifty million years ago, the ancestors of whales had to adapt their communication system to avoid drowning. Toothed cetaceans such as the current dolphin have evolved a nasal organ that allows them to make sounds.
Scientists have hypothesized that cetaceans, such as whales and blue whales, use their larynx to make sounds. But the mechanism of their anatomy that allows these songs was not really understood, recalls a Nature article accompanying the study.
Early sailors had already discovered these strange sounds, which were initially attributed to mythical creatures or to “the imagination of drunken sailors,” as American anatomist Joey Reidenberg recalls in the article.
Only after World War II did researchers gain access to sounds recorded by military hydrophones, where they understood that these songs were produced by whales.
In the Nature study, an international team led by Koen Elemans, from the Department of Biology at the University of Southern Denmark in Odense, combined experiments on the larynx of three enigmatic whale species (humpback whale, minke whale, sei whale) with anatomical and computer models. .
He concluded that these animals developed “unique laryngeal structures for sound production.”
-Two voices at the same time-
Once its lungs are full of air, after inhaling through its blowhole and closing the valves to keep out water, the whale produces its song by forcing air through its throat.
There it vibrates between the cartilage cords, just as air does between a human's vocal cords to produce sound. Before it passes into a pocket called the larynx, which allows it to be recycled towards the lung before a new vocalization is produced.
Quinn-Ellimans' discovery is an alternative, and perhaps a companion depending on the type, to the use of the fat pad over the cartilaginous cords. It would make it possible to produce another sound.
This observation was obtained by recording vibrations generated by airflow in laryngeal samples. Which is still impossible to observe in a living animal, given its size, says Joy Reidenberg.
However, she wonders whether the hypothesis emerging from the study could explain how some whales are able to produce at least two different sounds at the same time.
One limitation of the trial is that it was held outdoors with throat samples. This does not explain how sounds produced inside the animal can propagate out into the water, with all outlets closed.
The measurements by Quinn-Ellimans' team also set physiological limits on the frequency ranges, duration, and depth of songs that whales can emit.
Therefore, these sounds will occur at essentially the same depths and frequencies as sounds produced by marine traffic. Disrupting potential communication between cetaceans.
France Press agency
