A strange underwater sound whose source was a mystery for decades comes from minke whales, biologists have concluded. The finding, they say, has been accompanied by surprising new facts about the whale’s movements, and should yield more information.
The odd rhythmic sound was first reported by submarine sailors in the 1960s. They called it the “bio-duck” sound because they thought it sounded like a duck. Recorded since at various locations in the Southern ocean, it’s now being attributed to the Antarctic minke whale, Balaenoptera bonaerensis. The findings were published April 23 in the journal Biology Letters.
Last year, researchers put acoustic “tags” on two Antarctic minke whales in Wilhelmina Bay off the western Antarctic Peninsula. Scientists led by Denise Risch of National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center then analyzed the data and identified the sound.
A series of deep pulses, it’s heard mainly during the southern winter around Antarctica and off Australia’s west coast. No one knew those whales were there. The finding indicates some minke whales stay in ice-covered Antarctic waters year-round while others make seasonal migrations further north, the scientists said.
“These results have important implications for our understanding of this species,” said Risch. “We don’t know very much about this species,” she added, but the tags provide “an opportunity to change that, especially in remote areas.”
Scientists on a hard inflatable boat used poles to tag the animals. The tags recorded sounds, water temperature and pressure. No other marine mammal species were observed in the area when calls were recorded, the scientists said.
The scientists didn’t initially recognize the mysterious sounds as the “bio-duck,” instead attributing them possibly to submarines, some oceanographic phenomenon, or even fish. They made the connection to the “bio-duck” sound after checking published literature.
Minke whales, which have been victims of Japanese whaling expeditions, 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. Rorquals are rather streamlined, have pointed heads and, except for humpback whales, small pointed fins.
Source : http://www.world-science.net