Undersea Vibrations

They can keep the conversation going without wasting their breath.

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, like 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 uncovered how structures in the nose, called phonic lips, allow toothed whales to produce sounds in different registers, similar to the way humans speak, all while conserving air deep beneath the ocean's surface.

And the animals use what is called the vocal fry register for echolocation - the lowest pitch that can be produced by their vocal cords, a sound that has a creaky, drawn-out quality but one that requires a minimum amount of air to activate. The work was published in the journal Science recently.

Coen O.H.Elemans, a biologist in Denmark, and some colleagues inserted endoscopes into the nasal activities of trained Atlantic bottlenose dolphins and harbor porpoises to get high-speed footage during sound production.

They found that sound was indeed being produced in the nose. They confirmed the finding with experiments on dead harbor porpoises [beached or bycatch], filming the phonic lips as air was pushed through the nasal complex.

They saw that the phonic lips would briefly separate and then collide, causing a tissue vibration that would release sound into the surrounding water. [Sam Jones]


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