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updated 10/22/2012 12:49:45 PM ET 2012-10-22T16:49:45

Certain whales can imitate the voices of humans, according to a new paper that highlights the vocal mimicry skills of one whale in particular.

The marine mammal, a white whale named NOC, copied the sound of people so well that at first, researchers thought they were hearing humans conversing in the distance. A diver who worked with NOC once even left the water, wondering, "Who told me to get out?" The voice turned out to be that of NOC.

"They are highly vocal animals," lead author Sam Ridgway of the National Marine Mammal Foundation told Discovery News, adding that NOC was not the first to copy human speech.

"A major instance occurred at Vancouver Aquarium in 1979," he said. "In that case, people thought the whale uttered his name ("Lagosi") and other sounds that were like garbled German or Russian. Our whale was the second example, however, ours was the first solid demonstration using acoustic analysis including 'voice print' simultaneously with human speech."

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The study, described in the latest issue of Current Biology, revealed an amplitude rhythm in NOC's vocalizations that was comparable to human speech. Fundamental frequencies in the whale's vocalizations were also in the same range of human speech and were several octaves lower than the whale's usual sounds.

Ridgway said NOC spent long periods in close contact with humans, listening to them from both above and below the surface.

"The whale often heard divers talking over underwater communication equipment," he continued. "I think that vocal animals like feedback. Perhaps this figured in his motivation."

NOC also went to a lot of trouble to make the sounds. The researchers explain that the whale had to vary the pressure in his nasal tract while making other muscular adjustments and inflating the vestibular sac in his blowhole.

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NOC, who unfortunately passed away after 30 years at the National Marine Mammal Foundation, stopped making the human speech-like sounds after the age of 3 or 4 years old, Ridgway said. At the time, Ridgway presented the news at a scientific conference, but the work was not funded and became lost in the research shuffle until more recently, when colleagues encouraged him to publish the data.

There are a few possibilities as to why NOC stopped his human vocal mimicry while still a youngster.

The first is that hormonal changes related to sexual maturity may diminish a whale's urges to mimic. Another possible reason is that the novelty might have simply worn off for NOC.

Ridgway explained that "we trained the whale to interact with us acoustically for hearing test and for reaction time determinations, among other things. For this new work, the whale was responding to us vocally. These responses may have limited his interest in the human speech-like sounds."

William Schevill, now deceased, of Harvard University's Museum of Comparative Zoology, was the first to document spontaneous human voice mimicry in a white whale. Schevill and colleague Barbara Lawrence noted that "occasionally the calls would suggest a crowd of children shouting in the distance."

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The findings open up the possibility of teaching white whales how to speak, but that effort might not be worthwhile, Ridgway suggests.

"They readily learn," he said. "I think they could be taught many sounds. I do not know that teaching speech would be scientifically worthwhile."

© 2012 Discovery Channel

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