It is one of Earth’s most haunting sounds — the “singing” of baleen whales like the humpback, heard over vast distances in the watery realm. Now scientists have finally figured out how these filter-feeding marine mammals do it.
Baleen whales — a group that includes the blue whale, the largest animal in Earth’s history — use a larynx, or voice box, anatomically modified to enable underwater vocalisation, researchers said on February 21. They have evolved a novel structure — a cushion consisting of fat and muscle that sits inside the larynx, the researchers said.
That means baleen whales make their sounds with their larynx, as do humans, while toothed whales — including dolphins, porpoises, killer whales and sperm whales — evolved a different mechanism employing a special organ in their nasal passages.
It was recognised in the 1970s that baleen whales are very vocal, but precisely how they produce their array of sounds had remained unclear.
“These are among the most spectacular animals that have ever roamed our planet. They are highly intelligent, social animals that would have dwarfed most dinosaurs and feed on the smallest shrimp. They have the rare ability to learn new songs and spread their vocal culture across the planet,” said University of Southern Denmark biologist Coen Elemans, lead author of the study published in the journal Nature.
“To communicate and find each other in murky and dark oceans, baleen whales depend critically on the production of sound. For example, humpback females and their calves communicate with each other by voice, and humpback males sing to attract females,” Mr. Elemans added.
All baleen whales, also including the fin, sei, right, gray, minke, bowhead and others, make very-low frequency calls barely audible to humans. A few species including the humpback and bowhead produce the higher-pitched sounds that people would be more familiar recognising as whale songs.