Dolphins, pilot whales, and sperm whales use echolocation clicks to hunt and subdue their prey. But the animals, known as toothed whales, also produce other sounds for social communication, such as grunts and high-pitched whistles. For decades, scientists speculated that something in the nasal cavity was responsible for this range of sounds, but the mechanics were unclear.
Now, researchers have discovered how structures in the nose, called phonic lips, allow toothed whales to produce sounds in different registers, similar to the way the human voice works, while conserving air in the deep ocean. . And the animals use the vocal fry register for echolocation. Yeah, that vocal fry. The work was published in the journal Science Thursday.
Studying the structures responsible for the production of whale sound has not been an easy task. In the past few decades, “there’s been a lot of circumstantial evidence: people filming things with X-rays or triangulating sound with different hydrophones,” he said. Coen P.H. Elemansbiologist from the University of Southern Denmark.
Taking a new approach, Dr. Elemans and colleagues inserted endoscopes into the nasal cavities of trained Atlantic bottlenose dolphins and harbor porpoises to obtain high-speed imaging during sound production. They discovered that the sound was in fact produced in the nose. But to confirm that phonic lips were involved, and to see if their movement was driven by muscle or airflow, they created an experimental setup with deceased (stranded or incidentally captured) harbor porpoises, filming the phonic lips while the air it was pushed through the nose. complex. They saw that the phonic lips would briefly separate and then collide again, causing a vibration of the tissue that would release the sound into the surrounding water.
But relying on air-powered sound production doesn’t seem like the best idea if your food is in the murky depths.
“A thousand meters down, you have 1 percent of the air that you had at the surface,” he said. Peter Madsen, a zoophysiologist at Aarhus University in Denmark, who has been tagging toothed whales for decades and is a co-author of the study. “For me, it’s always been very provocative to watch a sperm whale, beaked whale or pilot whale dive deep, clicking happily, while having the knowledge in the back of my head that they’re supposed to use air for this.”
Using a combination of sound data from tagged toothed whales diving deeper than 3,000 feet and the high-speed video they had collected of animals alive and dead, the researchers stumbled upon a small sound that accompanies the loud echolocation click. . It turned out to be the brief millisecond opening of the phonic lips just before they snapped back together, indicating that the whales use air sparingly underwater and need very little to create a booming echolocation click. “Only about 50 microliters of air are used to generate the next click,” Dr. Madsen said.
This adaptation has great advantages. “You can go deeper and deeper if you need less air,” Dr. Elemans said, and that opens up a whole new world of food, like giant squid. “Sperm whales have access to that because they use this mechanism.”
“We knew that toothed whales had this vocal plasticity, which is key for them learning what sounds to make,” he said. Mauricio singer, a biologist at Oregon State University who was not involved in the study. But, he says, the study helps explain which structures are responsible. “We need this kind of detailed work so we can see its potential to learn and reproduce those sounds.”
The researchers were also able to classify the sounds into three distinct human-like vocal registers: the fry vocal register, the chest register (similar to the normal human voice), and the higher falsetto register (used for whistles). of the animals). ).
And they found that the echolocation clicks fall within the register of vocal fry. In humans, vocal fry, or “squeaky voice,” is a pronounced vocal pattern with Kim Kardashian and Alexis Rose from the TV show “Schitt’s Creek”, and people have a lot of feelings about it. Some find it irritating, which a study says could hinder the job prospects of young women who use it. but others see it as a sign of social status and success.
dr. Elemans said that, when it comes to vocal fry, “no matter what you think, whales are definitely very successful.”