Weird vocal fry trick helps orcas and dolphins hunt prey in the deep

Toothed whales such as orcas and dolphins use air-powered nose blasts to help them hunt prey hundreds of metres deep. The nasal-powered echolocation system works under extreme water pressure and lets the whales vocalise in different registers – an ability only seen before in crows and humans.

As top ocean predators, toothed whales frequently dive up to 2 kilometres deep in pursuit of prey. They echolocate using loud, rapid clicks, but researchers initially didn’t know how they were able to perform this feat because, at depths beyond 100 metres, whales’ lungs collapse. Previous research confirmed the sounds weren’t coming from the larynx – the voice-producing organ in humans and most mammals – but was instead radiating from the nose.

To understand how this works, Coen Elemans at the University of Southern Denmark and his colleagues trained two Atlantic bottlenose dolphins (Tursiops truncatus) and three harbour porpoises (Phocoena phocoena) to voluntarily accept an endoscope inside their blowholes. A high-speed camera affixed to the scope gave the team a peek inside each animal’s nose while they were echolocating for food in the open ocean. Tissue in their noses moved with each click.

In the lab, researchers pumped air through the nose of already deceased harbour porpoises and found that their tissues move in a similar manner – they identified the source as a narrow passage in the nose called phonic lips. When a toothed whale’s lungs collapse, it pushes oxygen into their muscles and sends a small amount of air into this nasal cavity. The air swishes back and forth through the phonic lips, helping the porpoises produce clicks as loud as 200 decibels – louder than a firework, and enough to permanently damage human ears.

“They basically push [air] one way and then recycle it and push it back without breathing,” says Elemans. “It certainly surprised us.”

Further sound analysis and digital models of the nasal tract showed that, like humans, toothed whales have at least three voice registers: the vocal fry register (a low, creaky voice), the chest register (a normal speaking voice) and the falsetto register (a high-pitched, squeaky tone). Their nose-echolocation trick is exclusively in the vocal fry register, which requires the least air flow to make a click.

Producing sound in the nose gives whales more control over the sounds they create and frees up the larynx for another important use: blocking airflow between the lungs and nose, letting pressure build in the nose during a deep dive without risking damage to the lungs.

“All the sounds they make are produced by these phonic lips that are in the nose… and the larynx [becomes] a really good plug,” says Elemans. “By doing that, they can make the loudest sound of any animal on earth by far.”

The discovery that toothed whales can produce sounds in different registers raises new questions about their communication, says Stefan Huggenberger at Witten/Herdecke University in Germany, who wasn’t involved in the work.

“Yes, they have different voices, but what for? And how do they use them?” says Huggenberger.

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