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.
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.
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.