A new study by San Diego researchers shows that whales hear sounds in the water through their bones, a discovery that could help protect the endangered mammals from man-made noise.
The research by San Diego State University biologist Ted W. Cranford and University of California San Diego engineer Petr Krysl reveals that the skulls of at least some baleen whales have acoustic properties that capture the energy of low frequencies and direct it to their ear bones. Using a computer simulation of a fin whale head, the two scientists discovered the animal’s skull amplifies and conducts low frequencies directly to their ear bones.
“Bone conduction is likely the predominant mechanism for hearing in fin whales and other baleen whales,” Cranford said.
Baleen whales are the largest animals on earth, and include blue whales, minke whales, right whales, gray whales and fin whales. These whales can emit extremely low frequency vocalizations that travel extraordinary distances underwater. The wavelengths of these calls can be longer than the bodies of the whales themselves.
All of these whales are considered endangered, with the exception of the gray whale, which recently was removed from the endangered species list, Cranford said.
Over the past few years, government regulators have been attempting to enact laws placing limits on the amount of man-made noise that baleen whales can be exposed to. These man-made noises come primarily from three sources: commercial shipping, energy exploration, and military exercises.
It’s possible these new findings will help legislators decide on limits to oceanic man-made noise, but Cranford stressed that what’s most important about their project is that they managed to solve a long-standing mystery about a highly inaccessible animal.
“What our contribution does is give us a window into how the world’s largest animals hear, by an odd mechanism no less,” Cranford said. “This research has driven home one beautiful principle: Anatomic structure is no accident. It is functional, and often beautifully designed in unanticipated ways.”
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