ScienceShot: Baleen Whales Use 'Ear Fat' to Hear

Whales use sound to communicate over entire oceans, search for food, and coordinate attacks. But just how baleen whales—a group that uses comblike projections from the roof of their mouth to catch food—heard these grunts and moans was something of a mystery. Toothed whales, including dolphins and porpoises, use lobes of fat connected to their jawbones and ears to pick up sounds. But in-depth analyses of baleen whales weren't previously possible because their sheer size made them impossible to fit into scanners such that use computed tomography and magnetic resonance imaging, which analyze soft tissues. So in a new study, published online this month in The Anatomical Record, researchers focused on one of the smaller species, minke whales (Balaenoptera acutorostrata). They found that triangular patches of fat surrounding minke whale ears (yellow patches, above) could be key to how they hear. They scanned seven minke whale heads in CT and MRI machines, created computer models of the ears and surrounding soft tissue, and dissected the whale noggins to reveal ear fat running from blubber just under the skin to the ear bones. This is similar to the arrangement found in toothed whales. The novel analysis allowed the authors to speculate that the ear fat in both toothed and baleen whales could have shared a common evolutionary origin.

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