http://www.digitaljournal.com/science/mystery-of-the-ocean-quack-solved/article/382173

Mystery of the ocean 'quack' solved

Posted Apr 26, 2014 by Tim Sandle
A mysterious oceanic quacking sound, which has remained unidentified for 50 years, has been shown to originate from minke whales.
The so-called “bio-duck” sound was first reported by submarine personnel in the 1960s. The recording, and subsequent observations, long remained a puzzle for scientists. Now there is an answer, according to Denise Risch, a bioacoustician at the US National Oceanic and Atmospheric Administration: the minke whale.
Minke whale is a name given to two species of marine mammal. The minke whales are the second smallest baleen whale; only the pygmy right whale is smaller. The minke whale is a black/gray/purple color.
Risch told BBC News: "Over the years there have been several suggestions . . . but no one was able to really show this species was producing the sound until now."
Risch and her colleagues clipped acoustic tags onto minke whales near Antarctic; from this they were able to determine that the whales were responsible for the strange 'quacking' sound. The bio-duck sounds come in sets spaced about 3.1 seconds apart.
The research finding now means that biologists can track the whales using these sounds and even go through the backlog of calls recorded from previous years to pick up on long-term patterns in migration and behavior.
Risch's findings have been published in the journal Biology Letters, in a paper titled "Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)".