Antarctic minke whales
April 24, 2014

Source Of Mysterious Duck-Like Sound In Antarctic Identified

redOrbit Staff & Wire Reports - Your Universe Online

Researchers have discovered the origins of a bizarre duck-like sound heard in winter and spring in the ocean around Antarctica and off Australia’s west coast.

The sound – a series of low-pitched, repetitive pulses dubbed “bio-duck” – was first recorded more than half a century ago, but its source has eluded scientists, until now.

Using acoustic recorders, researchers Denise Risch of NOAA's Northeast Fisheries Science Center (NEFSC) and colleagues discovered that the mysterious sound is actually the underwater chatter of the Antarctic minke whale.

“These results have important implications for our understanding of this species,” Risch said in a recent statement.

For instance, the findings indicate that some minke whales remain in ice-covered Antarctic waters year-round, while others undertake seasonal migrations to lower latitudes.

“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,” Risch said.

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.

In February 2013, an international team of researchers deployed acoustic tags on two Antarctic minke whales in Wilhelmina Bay off the western Antarctic Peninsula. The tags were the first acoustic tags successfully deployed on this species, and were placed on the animals using a hand-held carbon fiber pole by researchers working from a rigid-hulled inflatable boat. The tags also recorded the water temperature and pressure.

Risch and her team conducted an acoustic analysis of the data, and identified the minke whales as the source of the “bio-duck” sounds through comparisons with sounds in the published literature. They also matched recordings on long-term, bottom-mounted recorders from several other locations in the Antarctic.

No other marine mammal species were observed in the area when the calls were recorded, providing further evidence that the sounds originated from the tagged whale or other nearby Antarctic minke whales.

The researchers said the findings will allow them to interpret numerous long-term acoustic recordings, and improve understanding of the distribution, abundance, and behavior of this species.

Identifying the bio-duck sound will also allow for broader studies of the presence of minke whales in other seasons and areas, they said.

The findings are published April 23 in the journal Biology Letters.

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