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These whales can make at least two different sounds at once

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An international team of scientists has discovered that baleen whales can produce at least two different sounds at the same time. This is possible thanks to the specific structure of the larynx, which has developed through evolution.

Whales are known for their complex social and reproductive behavior. An integral part of it is its characteristic underwater singing. Scientists have long known that through evolution, whales were divided into those that use the nasal vocal organ to sing and those that use the larynx. However, the exact mechanism of air flow and sound production in water has not been known.

In the latest publication, which appeared on Wednesday in the journal Nature, an international team of scientists described the examination of the larynx of three stranded baleen whales – the melanoma whale (Balaenoptera borealis), minke whale (Balaenoptera acutorostrata) and humpback whale Megaptera novaeangliae. Experts have been able to prove that the U-shaped structure in the whale’s larynx is the equivalent of the paired vocal folds of land mammals. Unlike typical vocal folds in other mammals, the whale’s “U” fold is rotated 90 degrees so that it lies parallel to the trachea, and the gap between the “arms” of the fold leads to the laryngeal air sac.

Unique structure of the larynx

Publications dating back to the 1960s describe whale anatomy based on specimens obtained after the animals became stranded or examined at commercial whaling stations. These studies included depictions of the whale’s larynx, but did not link it to sound production or identify its internal structures as vocal cords. Although there are some similarities between the larynxes of whales and those of land mammals, it is still difficult to identify the source of whale songs and the mechanisms used by whales to produce sounds. Due to the large size of baleen whales, it is not possible to analyze the anatomy and functions of their vocal structures in captivity or examine them using modern visualization methods such as endoscopy or imaging techniques (including computed tomography and magnetic resonance imaging). “Small cetaceans such as dolphins, which can be more easily studied in captivity, are poor models because they vocalize at a different frequency than large baleen whales and use nasal structures instead of folds. Therefore, assumptions about baleen whale vocalizations are usually based on comparative analyzes of anatomy.” wrote Joy Reidenberg, the author of the article.

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The researchers used scanning and modeling techniques to reconstruct how vocalization might occur. In all three whale cases, it was found that the sound was produced by aerodynamic vibrations of specific vocal structures in the baleen larynx, which are not observed in toothed whales. These specialized designs allow sound production and airflow while preventing water inhalation.

At least two different sounds

Scientists have also determined that a single whale can produce at least two different sounds at the same time. Sound generation by vibration of the fat folds can occur on both sides of the larynx because the U-shaped fold has two arms. Joy Reidenberg noted that the main limitation of the scientists’ work was that they could only test isolated larynxes taken from whale bodies, which were then artificially suspended in the air. Therefore, the natural path of underwater sound production through a whale’s vibrating larynx remains unknown. It is also unknown how the sound reaches the water. “The evolutionary picture won’t be complete until we understand how the air-powered system that generates sound and transmits it to the mouth of land mammals became adapted to work underwater for whales. This, in turn, could help us decipher how Baleen whales make unusual sounds,” Reidenberg wrote.

Oceanic longfin whale, humpback whaleShutterstock

Fish fish

Baleen whales (Mysticeti) are a group of whales that include 15 species. Its smallest representative – the little whale (Caperea marginata) can reach a length of six meters, and the largest – the blue whale (Balaenoptera musculus), which is also the largest known animal living on our planet, 34 meters long. These animals do not have teeth, so they use baleen, or plates hanging from the palate, to filter huge amounts of food from seawater.

PAP, nature.com, eurekalert.org

Main photo source: Shutterstock



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