THE MYSTERY OF a weird duck-like sound, which has been heard off Australia’s west coast for decades, has finally been solved.
Scientists are now positive that the noise is being made by – no, not a duck – the Antarctic minke whale.
The source of a unique rhythmic sound, heard in the Southern Ocean, has baffled researchers for decades. In the 1960s, it was labelled the ‘bio-duck’ by submarine personnel who thought it sounded like a duck.
Past theories tried to attribute the noises to submarines, some oceanographic phenomenon or even some fish.
This week, a group of scientists led by Denise Risch, published its conclusive evidence that bio-duck is, in fact, a whale. Or lots of whales.
In February, the team deployed the first ever acoustic tags on two Antarctic minke whales in Wilhelmina Bay, just off the western Antarctic Peninsula.
The data collected by the tags was then analysed. The sound is described as a series of pulses in a highly repetitive pattern.
The bio-duck’s presence in higher and lower latitudes during the winter season also contributed to its mystery. No one knew the minke whales were there.
The identification of the Antarctic minke whale as the source of the sound now indicates that some minke whales stay in ice-covered Antarctic waters year-round, while others undertake seasonal migrations to lower latitudes.
“These results have important implications for our understanding of this species,” said Risch, a member of the Passive Acoustics Group at the NEFSC’s Woods Hole Laboratory. “We don’t know very much about this species, but now, using passive acoustic monitoring, we have an opportunity to change that, especially in remote areas of the Antarctic and Southern Ocean.”
No other marine mammal species were observed in the area when calls were recorded, providing further evidence that the recorded sounds were produced by the tagged whale or other nearby Antarctic minke whales.
Findings from this study will allow researchers to interpret numerous long-term, acoustic recordings, and improve understanding of the distribution, abundance, and behavior of this species.
Minke whales are the smallest of the “great whales” or rorquals, a group that includes the blue whale, Bryde’s whale, and humpback, fin, and sei whales. Rorqual whales are relatively streamlined in appearance, have pointed heads and, with the exception of humpback whales, small pointed fins.
The authors believe that by identifying the bio-duck, further studies can be carried out in other areas – and during other seasons. This study took place during the austral winter.
The ability to monitor the creatures will allow scientists to inform themselves about the species which inhabits an environment that is difficult to access, has changing sea-ice conditions and ”has been the subject of contentious lethal sampling efforts and international legal actions”.
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