Dolphins, porpoises, killer whales, sperm whales and different toothed whales produce an array of sounds – to search out prey using a sonar-like system known as echolocation and to speak with different members of their species.
| Photo Credit: Reuters
Dolphins, porpoises, killer whales, sperm whales and different toothed whales produce an array of sounds – to search out prey using a sonar-like system known as echolocation and to speak with different members of their species.
The actual mechanism they use had lengthy remained puzzling – till now. It seems it is all in the nose.
Researchers on Thursday provided a complete rationalization for sound production by toothed whales – loud clicks for echolocation, and softer burst pulses and whistles for communication. It is an air-driven system in the nose, analogous to the larynx, or voice field, in people and different mammals and the comparable syrinx in birds.
These marine mammals, possessing giant and sophisticated brains, have been utilizing echolocation – bouncing high-frequency sounds off underwater objects – to catch prey like fish and squid for tens of thousands and thousands of years.
“Echolocating toothed whales make the loudest sounds in the animal kingdom by forcing highly pressurized air past structures called phonic lips in their nose,” mentioned Peter Madsen, a sensory physiology professor and skilled in whale biology at Aarhus University in Denmark, co-leader of the examine printed in the journal Science.
“The phonic lips open for about one millisecond, and when they slap back together they create a tissue vibration that forms a very loud click in the water in front of the whale that is used to echolocate prey down to more than 1,000 meters (0.6 miles) depth,” Madsen added.
The phonic lips encompass connective tissue and fats.
The sound produced was discovered to function at completely different vocal registers like the human voice: “fry register” for clicks, “chest register” for burst pulses and “falsetto register” for whistles. In folks, the fry register represents the lowest tones, chest register the regular talking voice and falsetto register greater frequencies.
“The sounds are made by the same mechanism, namely air flow-induced self-sustained oscillations. But the critical difference is that in humans and other land mammals, air is used both as the propellant that makes the vocal folds vibrate and as the medium in which the sounds are propagated,” mentioned examine co-leader Coen Elemans, a University of Southern Denmark bioacoustics professor and skilled in animal sound production.
“In toothed whales, air is only used to drive the phonic lips that then, via tissue acceleration, generates a click that propagates through tissue in the nose and then into the water,” Elemans added.
Through evolution, sound production moved in whales from the trachea, or windpipe, into the nose.
Because little or no air is used per click on and since the whales can recycle the air, the analysis solved how deep-diving whales could make sound with out utilizing a lot air.
“Both laryngeal and synringeal sound production rely on pressurized air from the lungs, but that will not work for deep-diving toothed whales because their lungs collapse due to high hydrostatic pressures at deep depths. By pressurizing the phonic lips with an air reservoir in the nose, they can still make sounds in the deep sea,” Elemans mentioned.
The researchers used sound-recording tags on sperm whales, false killer whales and bottlenosed dolphins to review sound production in the wild. They used video from an endoscope, a skinny, tube-like instrument, to picture the phonic lips in harbor porpoises and bottlenosed dolphins in captivity. They additionally imaged phonic lip operation and anatomy in useless stranded porpoises.
The sounds made by toothed whales differ from the haunting “singing” by filter-feeding baleen whales.
“Toothed whales don’t sing like baleen whales,” Madsen mentioned. “It is believed that baleen whales use their vocal folds in the larynx like other mammals, but we still don’t know how baleen whales actually make sound. During the course of evolution, toothed whales have lost their vocal folds, but evolved an entirely new set of sound sources in the nose.”
