03/17/2015 10:55 EDT | Updated 05/17/2015 05:12 EDT

Baleen whales hear through their skull bones, researchers find

Some animals hear with protruding ears. Baleen whales like humpbacks, blue whales, minke whales, right whales, gray whales and fin whales? They hear with their skull bones. That is, according to new U.S. research.

The mystery of how baleen whales hear as long stumped scientists.

The whales emit extremely low frequency vocalizations that can travel long distances under water. The wavelengths of the sounds can be even longer than the whale's body.

"It turns out the animal's ear complex is rigidly wedged into the skull bones," said San Diego adjunct assistant biology professor Ted Cranford in an interview with On The Island.

"And when the skull moves … in response to these long wavelengths, that's how these ears are stimulated."

Cranford is part of a team of researchers from San Diego State University and the University of California, who believe they've cracked the question of how these majestic animals, occasionally spotted off B.C.'s coast, hear.

He said it appears that baleen whales — which feed through a mouth filter instead of teeth — hear differently to toothed whales, which sense when shorter wavelengths go through the soft tissue of their ear bones.

How much can baleen whale hear?

The baleen whale research, published in the journal PLOS One, was prompted by concerns over the amount of man-made noise in our oceans.

Cranford said he and his colleagues obtained a fin whale's head roughly 10 years ago, when rescue crews failed to save a baby whale that had washed up on a Los Angeles beach.

But he and his team began studying their specimen when government regulators tried to enact laws placing limits on the amount of man-made noise to which baleen whales can be exposed.

"Entities that make noise in the ocean — like the shipping industry or the energy exploration or production industry — they were saying, 'Gee whiz. How can you make regulations that we'll have to follow, when you don't even know how these animals can hear or how sensitive they are to these sounds that we're putting in the ocean?'" Cranford said.

"So there was this urgency to figure out how these animals hear and how sensitive they are to these low frequencies."

Now that scientists understand how baleen whales hear, Cranford says, he will study whether the direction of the sound waves impact the animals' hearing.

All species of baleen whales, except for the gray whale, are considered endangered.

To hear the full interview with Ted Cranford, click on the audio labelled: Mystery of baleen whale's hearing may be solved