How whales can sing – 02/22/2024 – Science

Unusual details of the anatomy of the larynx explain how whales manage to emit their calls underwater, communicating over distances of several kilometers with potential partners and rivals. Apparently, a “pad” of fat strategically positioned in the throat of giant mammals is responsible for enhancing their vocal abilities.

These conclusions come from a new analysis of the animals’ anatomy, published in the specialized journal Nature by European and American scientists. The data from the team led by Coen Elemans, from the University of Southern Denmark, applies to species in the mysticete group, which includes cetaceans with filter plates in place of teeth, such as humpbacks and blue whales (the latter are, as far as we know, the largest animals of all time).

In fact, the mystery about the production of vocalizations refers only to mysticetes because the other group of cetaceans, the odontocetes (animals with teeth, such as dolphins, orcas and sperm whales), have a more studied and well-researched system of producing calls. understood. Dolphins, orcas and others use their nasal apparatus — which, in land animals, would be the nose — to make sounds.

However, it is much more difficult to study mysticetes, taking into account, for example, their enormous size, which makes captive breeding unfeasible. Therefore, the team led by Elemans had to work with larynges extracted from individuals belonging to three species (sei whale, minke and humpback) – the whales had died of natural causes.

The anatomical structures extracted from the whales first underwent computed tomography sessions. Most importantly, the researchers developed an in vitro system that allowed them to simulate the passage of air and the production of sounds in the larynx – as if dead animals were “speaking Whale” again. Finally, the scientists used all this data to feed a computer simulation of how the vocalizations of the three species would be produced.

The team’s conclusion is that the whales in the group modified the ancestral vocalization pattern of mammals, based on the vibration of the vocal folds (also known as “vocal cords”) of the larynx. In the case of cetaceans, the main vibratory interaction involves these folds, which have a U-shape, and the cushion formed by an accumulation of adipose tissue above them.

“This result indicates that the air follows an alternative path that goes from the side to the center of the larynx, and not from top to bottom of it, as previously believed,” writes Joy Reidenberg, who works at the Hospital’s Functional Anatomy and Morphology Center. Mount Sinai, in New York, and commented on the study at the request of Nature. “The presence of two different places where vibrations can occur enhances the whales’ vocal abilities, and I wonder if this is what allows them to produce two distinct sounds simultaneously,” another famous ability of these species.

This vocal structure, however, has a negative side as well. According to the simulations carried out in the study, the characteristics of the whales’ larynx limit the sounds they can produce to a range of sound frequencies that, unfortunately for them, have a large overlap with the noises coming from human vessels.

In other words, it is as if the “pirate radio” of human traffic was disrupting the communication of these species. It is not simple to resolve this frequency overlap, but restricting the passage of vessels in key areas for whale feeding and reproduction could bring some relief.