Bio-duck

Bio-duck is the name given to a previously unidentified sound recorded in the Southern Ocean, specifically in Antarctic waters and off the west coast of Australia. It was first reported in 1960 by submarine personnel, who gave the sound its name, associating it with that of a duck. Once dubbed "one of the largest still unresolved mysteries of the Southern Ocean", the origin of the sound remained a mystery for decades until 2014, when it was concluded that the sound originated from Antarctic minke whales (Balaenoptera bonaerensis).

The recorded sound has a frequency range between 60 and 100 Hz, harmonics up to 1 khz, and an interval of 1.6 to 3.1 seconds between each sound. The sound is mainly present during the austral winter in the Southern Ocean, and is made near the surface, predominantly before feeding dives. Although the role of the sound remains a mystery, it is suggested that it could play a role in mating.

Researchers say that this discovery is significant in estimating seasonal occurrence, migration patterns and abundance of the Antarctic minke whales as acoustic research is more cost-effective than visual sightings and can be carried out regardless of weather and daylight conditions. Moreover, acoustic research is invaluable since Antarctic minke whales inhabit areas of high sea ice, making conventional ship-based research challenging.