How Baleen Whales Hear Super Low Frequencies Through Their Bones

Understanding how baleen whales hear has often puzzled marine mammal researchers. These massive animals sing complicated songs to one another that obviously can be heard; however, scientists have been unable to explain how whales capture the energy of low frequencies and direct it to their ear bones. Now, they may have an answer.

Baleen whales are also known as mysticetes, and are among the largest animals on Earth. This group of whales includes blue whales, minke whales, right whales, grey whales and fine whales. These whales have the ability to vocalize at extremely low frequencies that can travel extraordinary distances underwater. In fact, the wavelength of these calls can be longer than the bodies of the whales themselves.

In order to better understand these whales, the researchers looked at the remains of a young fin whale that had beached in California and later died. The scientists placed the whale's head in an X-ray CT scanner in order to get a better look at the whale. The researchers then employed a technique known as finite element modeling that breaks up data representing the skull and other parts of the head into millions of tiny elements and tracks their relationship with one another.

The researchers then simulated a sound wave passing through this computerized skull. This revealed how each miniscule component of bone vibrates in response.

"Bone conduction is likely the predominant mechanism for hearing in fine whales and other baleen whales," said Ted Cranford, one of the researchers, in a news release. "This is, in my opinion, a grand discovery."

The findings reveal a bit more about how whales manage to hear underwater. Not only that, but it may also help legislators decide on limits to oceanic human-made noise.

"What our contribution does is give us a window into how the world's largest animals hear, by an odd mechanism no less," said Cranford. "This research has driven home one beautiful principle: Anatomic structure is no accident. It is functional, and often beautifully designed in unanticipated ways."

The findings are published in the journal PLOS One.

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