Blue Whales Sing at Same Pitch, Study Says

John Roach
for National Geographic News
May 17, 2004

Luciano Pavarotti they're not, but if blue whales ever build up a repertoire they could give the Italian opera singer a run for his money. The cetaceans have perfect pitch. So perfect, in fact, that it's impossible to tell individuals apart from their calls.

"You might think that a big whale makes a lower sound than a small whale—they come in all different sizes—but they all make the same pitch," said Roger Bland, a physicist at San Francisco State University in California.

Bland, who took an active interest in underwater acoustics 12 years ago as a way to spend more time with his water-loving kids, would like to figure out how to tell individual blue whales (Balaenoptera musculus) apart from their calls.

Such an identification mechanism may allow conservationists to keep better tabs on blue whale populations, but so far the task has proven fruitless.

John Hildebrand, an expert on marine, mammal acoustics at the University of California San Diego's Scripps Institution of Oceanography in La Jolla, said Bland's finding correlates with his own observations.

"The whales clearly work to synchronize the frequency of their calls," he said. "They must do this despite a range of sizes of animals."

Call Pattern

Bland and colleague Newell Garfield based their research on analysis of blue whale sound recordings captured with hydrophones (devices for detecting sound transmitted through water) on top of a seamount 60 miles (95 kilometers) offshore from Half Moon Bay, California. (See sidebar.)

Since the researchers only hear and see the sounds as played back over a sonogram (a device for visualizing sounds), they're not certain as to which or how many whales are responsible for the calls they detect.

"Some biologists are skeptical that we are listening to more than one whale, but I think there is enough information to make it clear that it is different whales at the same pitch," Bland said.

Bland and Garfield often detect overlapping patterns of the two distinct blue whale calls: the A call and B call. This overlap indicates the presence of more than one whale. The A call is a series of short pulses that sounds like a person gurgling mouthwash and the B call is a long, low groan.

The A call usually precedes the B call, but sometimes only the B call is heard. "If we keep at it long enough, we could find that the thing that distinguishes individuals is small variations in the pattern, but at the moment we've only got the pattern," Bland said.

Continued on Next Page >>




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