Unweaving the Song of Whales

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For nearly a decade, Cornell University researcher Christopher Clark has been eavesdropping on the ocean, hoping to decipher the enigmatic songs of whales.

Using old US Navy hydrophones once employed to track submarines, he has collected thousands of acoustical tracks of singing blue, fin, humpback and minke whales. His bioacoustics lab is now able to pinpoint the location of individual singers, and determine the length of their song. As a result, he’s had to redraw the map of whale acoustics.

“The range is enormous,” explained Dr Clark.

“They have voices that span an entire ocean.”

Drawing on newly declassified acoustic data from the Sound Surveillance System (SOSUS), and using new tools that can crunch high volumes of them, Dr Clark has determined that whales’ songs travel over thousands of kilometres and also that increasing noise pollution in the oceans impedes the animals’ ability to communicate.

Booming voices

It is not certain whether whales thousands of kilometres apart communicate directly with each other, or what their messages contain. But the results support a 30-year theory that, before the advent of modern shipping, the animals’ booming voices would have resounded from one ocean basin to another.

With sound that is loud and low, in other words, “beautifully designed” for long distance travel, the singing of a whale in the waters off Puerto Rico could carry 2,600km to the shores of Newfoundland, says Dr Clark.

When scientists create a digital map of the sound as it propagates in the water, it “illuminates the entire ocean”, he adds.

The pan-oceanic range is fitting for massive 30-190-tonne creatures that rely on reflected sound, rather than light, to navigate.

“You are dealing with animals that are highly acoustically oriented,” said Dr Clark. “Their consciousness and sense of self is based on sound, not sight.” Dr Clark and other whale researchers spoke at the recent annual meeting of the American Association for the Advancement of Science in Washington DC about how new technologies are revealing whale secrets at the same time that human activity continues to threaten their well-being.

He is particularly concerned with noise pollution, or “acoustic smog”. Noise from shipping vessels doubled every decade, said Dr Clark, which means a whale’s world decreases by a factor of two.

Over 20 years, its 1,600km acoustic radius shrinks to 400 km, and, presumably, limits the range over which animals can navigate and find food or mates.

“We are slowly, inexorably, raising the tide of ambient noise so that their worlds are shrinking just to the point where they’re dysfunctional,” Dr Clark believes.

Source BBC.

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http://news.bbc.co.uk/1/hi/sci/tech/4297531.stm