An international team of researchers have finally discovered the source of a weird, low-frequency rhythmic sound that has puzzled scientists and submarine sonar operators for more than half a century. Listen to it.
No kaijus, folks. It's the Antarctic minke whale or Balaenoptera bonaerensis. The fact that the sound appeared "in higher and lower latitudes during the winter season" was also something that contributed to its mystery.
First described and named by submarine personnel in the 1960s who thought it sounded like a duck, the bio-duck sound has been recorded at various locations in the Southern Ocean, but its source has remained a mystery, until now.
In February 2013, an international team of researchers deployed acoustic tags on two Antarctic minke whales in Wilhelmina Bay off the western Antarctic Peninsula. These tags were the first acoustic tags successfully deployed on this species. The acoustic analysis of the data, which contained the bio-duck sound, was led by Denise Risch of NOAA's Northeast Fisheries Science Center (NEFSC) and was published April 23, 2014 in Biology Letters.