Dolphins and other toothed whales are large-brained top predators that captivate our imagination; they are extremely social, cooperate, and can hunt prey in complete darkness down to two km deep using echolocation.
All of these extraordinary behaviors are mediated by sound, which travels far and fast in murky and dark waters.
However, how these amazing animals create their rich vocal repertoires in the deep has remained a mystery.
According to a new study published in the journal Science, toothed whales evolved an air-driven nasal sound source that operates at different vocal registers, similar to the human voice.
Toothed whales catch food in the deep using vocal fry
(Photo : LOIC VENANCE/AFP via Getty Images)
Professor Coen Elemans, a voice scientist at the Department of Biology at the University of Southern Denmark, and Professor Peter Madsen, a whale biologist at Aarhus University in Denmark, led the study, as per ScienceDaily.
According to the findings, toothed whales, like humans, have at least three voice registers: the vocal fry register (also known as the creaky voice, which produces the lowest tones), the chest register (our normal speaking voice), and the falsetto register (which produces even higher frequencies).
"Vocal fry is a common voice register in American English; Kim Kardashian, Kate Perry, and Scarlet Johannsen are well-known users of this register," Professor Elemans explained.
Toothed whales can dive as deep as 2,000 meters and catch more fish than humans.
To locate, track, and catch prey in deep and murky waters, they produce short, powerful ultrasonic echolocation clicks at rates of up to 700 per second.
According to Madsen, vocal fry provides whales with access to the richest food niches on the planet: the deep ocean.
While vocal fry can be perceived as anything from annoying to authoritative in humans, Elemans believed it has undoubtedly made toothed whales an evolutionary success story.
It was previously thought that toothed whales made sounds with their larynx, just like other mammals, but 40 years ago it was discovered that this is not the case; they produce sound through their nose.
The Danish research team discovered what exactly happens using high-speed video through endoscopes in the new study
The toothed whales have evolved an air-driven sound production system in their nose that functions physically similarly to laryngeal and syringeal sound production in mammals and birds - but it is not in the same location.
At depths greater than 100 meters, whale lungs collapse to avoid compression sickness, and the remaining air is found in the nasal passages of the skull.
This creates a small but sufficient airspace to produce echolocating sound at depths of up to 2000 meters.
When echolocating, toothed whales pressurize the air in their bony nose and allow it to pass through structures known as phonic lips, which vibrate similarly to human vocal folds.
Their speed causes sound waves to travel through the skull to the front of the head.
In addition to echolocation, toothed whales produce a diverse range of sounds as part of their complex social communication.
The researchers demonstrate in their study that these sounds are produced by the phonic lips vibrating in the chest and falsetto registers.
They captured the phonic lips using a variety of methods, including trained dolphins and wild animals moving freely with a small tag that recorded their sounds.
The in vivo recordings were made at the Dolfinarium Harderwijk in the Netherlands.
Also Read: 5 Reasons Why You Should Not Go Whale Watching
From Vocal Fry To Falsetto
The researchers discovered that toothed whales, like humans, use distinct vocal registers to create their diverse sounds, as per AAAS.
A vocal register in humans is a range of tones produced by a specific vibratory pattern of the vocal folds in the larynx.
The chest register (normal speaking voice), vocal fry (a low creaky voice), and falsetto are examples of these.
Whales use similar registers when making sounds for different functions, according to the researchers.
The vocal fry register, for example, is used to produce echolocation clicks, whereas the falsetto register is used in higher-pitched whistles for social communication.
Understanding how whales make these sounds in the nose will allow us to understand the limits of their sound production in the future, which will allow us to understand to what extent the animals can call louder or differently in the face of increasing anthropogenic noise at sea.
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