Researchers have solved the mystery of a "duck quack" sound heard in the Southern Ocean.
The rhythmic noise, dubbed the "bio-duck" has been a mystery since it was first heard by a submarine crew in the 1960s, a Northeast Fisheries Science Center news release reported.
Researchers have finally traced the bio-duck to the Antarctic minke whale (Balaenoptera bonaerensis). To make their findings the researchers fitted two of the whales with acoustic tags.
The sound was never linked to the minke whales in the past because researchers were unaware that they were there; this finding indicates some of the whales stay in the ice-covered Antarctic all year instead of migrating.
"These results have important implications for our understanding of this species," Denise Risch of NOAA's Northeast Fisheries Science Center (NEFSC) said in the news release. "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."
The tags were attached using a "hand-held carbon fiber pole," the news release reported. The researchers applied the devices from an inflatable boat. The tags also recorded water temperature and pressure and allowed the team to visually track the whales during the day.
No other animals were observed in the area the calls were recorded, which suggest the bio-duck is emitted by the minke whales.
In the past researchers thought the "series of pulses in a highly repetitive pattern" came from submarines, fish, or an "oceanographic phenomenon," the news release reported.
The team hopes this research will help provide insight into the "distribution, abundance, and behavior" of the minke whales, which are the smallest of the "great whales" category. This group also includes " blue whale, Bryde's whale, and humpback, fin, and sei whales," the news release reported.
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