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50-year-old mystery of the ocean quack solved

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Press Trust of India Washington
Last Updated : Apr 24 2014 | 4:14 PM IST
Scientists have finally solved the 50-year-old mystery behind a bizarre duck-like sound heard every winter and spring in Southern Ocean, finding that this acoustic phenomenon is caused by Antarctic mink whales.
For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery, researchers said.
Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast.
"Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis)," researchers wrote in the journal Biology Letters.
"It was hard to find the source of the signal. Over the years there have been several suggestions but no-one was able to really show this species was producing the sound until now," lead researcher Denise Risch, from the US National Oceanic and Atmospheric Administration (NOAA) Northeast Fisheries Science Center in Massachusetts, said.
Scientists analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular down-sweeps that have previously been attributed to this species.

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"This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales." researchers said.
This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action, researchers said.
Bio-duck or the mysterious quacking-like sound was first reported in the open ocean by submarines in the 1960s.
The sounds were originally detected by sonar operators on Oberon class submarines. They are audible with frequencies from 50 to 300 Hz. The duration of the calls are 1.6 and 3.1 seconds.

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First Published: Apr 24 2014 | 4:14 PM IST

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