Humpback whales use songs to communicate with each other across the ocean KARIM ILIYA
Biologists have figured out how baleen whales produce their signature songs – and it involves their uniquely shaped larynx.
Baleen whales, including humpbacks, communicate with complex songs that can be heard over vast distances. “People recorded the first whale sounds in the 1970s, but it was only very recently that we started to appreciate the different sounds these animals actually made,” says Coen Elemans at the University of Southern Denmark. “Now, the question is, how do they even do this?”
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To learn more, Elemans and his team extracted the larynxes of three recently deceased baleen whales: a sei whale (Balaenoptera borealis), a humpback whale (Megaptera novaeangliae) and a northern minke whale (Balaenoptera acutorostrata).
The larynx, commonly known as the voice box, is an organ that sits at the top of the neck in mammals. When air flows through the organ, folds of tissue vibrate, resulting in sound.
But that isn’t the case with baleen whales, says Elemans. Upon examination of the whales’ larynxes, the team found that they had an unexpected shape – with a cushion of fat sitting on one side of the organ.
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As these whales breathe, the air is pushed against the fatty material, which causes it to vibrate and make sounds. “We’ve never seen this in any other animal,” says Elemans. “It’s totally unique to baleen whales.”
The whales also can recycle the air in their lungs, which comes in handy when they are submerged for long periods of time. When they breathe out through their windpipe and larynx, the air goes into a sac with a contracting wall that expels the air back into their lungs.
From a computer model of the larynx, the team found that baleen whales could produce frequencies up to 300 Hertz, at a maximum depth of 100 metres below the surface of the sea. That is within the frequency range of noise made by ships, raising concerns that shipping noise could drown out their songs.
“These whales cannot escape this,” says Elemans. “So we need take steps to reduce the noise we make.”
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