Research shows how noise pollution, i.e. noise caused by humans, limits the ability of whales to communicate. Nevertheless, they continue to sing, but can hardly hear each other.
By dissecting three specimens that scientists recently found stranded dead, they have uncovered the secrets of their melodies, the result of their larynx being redesigned over hundreds of years to be able to communicate over long distances.
How is whale communication?
Different groups of whales have adapted to their new environment: toothed whales (e.g. dolphins, killer whales and sperm whales) have developed a nasal vocal tract capable of producing high-frequency sounds, and in the case of dolphins, they use it for echolocation.
Meanwhile, baleen whales (such as blue whales, humpback whales and fin whales) have almost completely changed the structure of their larynx. This organ, one of the most complex in mammals, performs two functions: on the one hand, protection of the airways and lungs, and on the other hand, pronunciation.
The ancestors of whales lived on land around 50 million years ago and had to adapt their anatomy to the aquatic environment during their rapid development. For example, they moved the vent to the neck to make it easier to breathe in water and increase lung capacity.
But in some cases they have also had to adapt their communication skills, for which they have developed a powerful larynx that allows them to regulate and amplify sounds underwater and create modulations that refer us to the melody of the songs.
This is the case of the baleen whales or Mysticetes, an order of whales characterized by the presence of baleen instead of teeth, which includes bowhead whales, humpback whales and blue whales, among others.
Unlike humans and other mammals, these whales do not have vocal cords, but do have a U-shaped pattern that allows them to inhale large amounts of air and layers of fat and muscle that other animal species do not have.
While their cousins, the odontocetes, developed vocal organs in their noses, baleen whales did the same with their larynx, allowing them to expel large amounts of air with great force, producing sounds with a range of up to hundreds of kilometers.
Effects of noise pollution on marine mammals
Even a whale communication system that has worked exceptionally well for millions of years is not immune to an inexorable increase in noise levels caused by human activity.
This is exactly what emerges from the current study published in the specialist journal Naturecarried out by a team of Austrian and American researchers.
To conduct the study, scientists collected larynxes from several specimens of different species and designed a laboratory experiment. They blew air into these voice devices and checked how they worked and produced low-frequency sounds.
They found that these animals can reuse airflow and direct it into the lungs multiple times to create new sounds. However, they also discovered that these oral devices “insurmountable physiological limitations at certain depthsThis means that they cannot prevent anthropogenic noise caused by noise pollution from ships close to the surface.
In particular, they concluded that they could only produce distinct sounds at depths of up to 100 meters, but could no longer communicate in the same way at greater depths.
Underwater sounds for communication
Marine mammals, including whales, use underwater sound as a primary means of communication and environmental assessment. Sound waves are essential for communication, but also important for navigation and foraging.
Therefore, the acoustic ecology of whales and other cetaceans contains many “moods”, from the vocalizations that allow them to distinguish their species, to the detection of all natural processes such as wind, rain and even earthquakes.
In whale communication, scientists have occasionally observed that some sperm whales can accurately identify specific members of their family. They make a series of specific clicks with subtle inflections, as if it were the name of their loved one.
However, with the advent of the industrial age, humans have drastically changed this soundscape.
It turns out that the sound pressure in water is higher than in air, so pollution is also more dangerous as it can affect many important aspects of the life cycle of these animals, including their basic biological functions, from vocalizations for communication to for mating Orientation and echolocation of their prey can be fatal for these animals.
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