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Ted Cranford, San Diego State University

Whale skulls act like antennas, CT scans reveal

Whales can sing, buzz, and even whisper to one another, but one thing has remained unknown about these gregarious giants: how they hear. Given the size of some whales and their ocean home, studying even the basics of these mammals has proved challenging. But two researchers have now developed a way to determine how baleen whales such as humpbacks hear their low-frequency (10- to 200-hertz) chatter, and they found some bone-rattling results.

Baleen whales have a maze of ear bones that fuse to their skull, leading scientists to suppose the skull helps whales hear. Under this premise, the researchers used a computerized tomography scanner meant for rockets to scan the preserved bodies of a minke whale calf (Balaenoptera acutorostrata) and a fin whale calf (B. physalus), both of which had stranded themselves along U.S. coasts years before and died during rescue operations. Their preserved bodies were kept as scientific specimens. The researchers used these body scans (an example of which is displayed above) to produce 3D computer models to study how the skull responded to different sound frequencies. The skull acts like an antenna, the scientists reported today in San Diego, California, at the 2018 Experimental Biology conference, vibrating as sound waves impact it and then transmitting those vibrations to the whale’s ears. For ease of viewing, the scientists amplified the vibrations 20,000 times.

Whale skulls were especially sensitive to the low-frequency sounds they speak with, the researchers found, but large shipping vessels also produce these frequencies. This new information could now help large-scale shipping industries and policymakers establish regulations to minimize the effects of humanmade noise on these ocean giants.