Strange quacking noises heard in the oceans have baffled scientists over the years. Finally, a recent study has shed light on the mystery of the 'quacks' heard underwater. No, they are not ducks. The noises are made by the minke whales.
The study, which was published in the journal Biology Letters of the Royal Society Publishing, revealed that the "bio-ducks" sounds picked up by hydrophones were resonated by the Balaenoptera bonaerensis or the Antarctic minke whales.
These minke whales thrive in the oceans of the Southern Hemisphere. During summer, they migrate close to Antarctica. For the winter, they move north. The Antarctic species adopt a migration track that is opposite of their dwarf form, the common mink whales.
"The acoustic identification of Antarctic minke whales offers the opportunity to retrospectively analyze several years' worth of existing long-term recordings to explore seasonal occurrence and migration patterns of the species, including the possibility of using acoustics to estimate abundance," lead author of the study Denise Risch, who is also from the US National Oceanic and Atmospheric Administration (NOAA) Northeast Fisheries Science Center in Massachusetts, wrote.
Data showed that the eerie sounds, which range from 50 to 300 Hertz, were heard as early as the 1960s, and have since been recorded at various locations particularly in the Southern Ocean, the study said.
It was William Watkins of the Woods Hole Oceanographic Institution who first detected it in 1989 while studying U.S. Navy underwater recordings. Located in waters off of Kaneohe, Hawaii, and San Diego, Calif., U.S. Navy submarines allegedly recorded a "boing" noise.
On March 1, 1999, the sound was extremely loud not to be heard in the hydrophone system, reverberating in the entire Equatorial Pacific Ocean. It was initially thought of as a sound produced by an iceberg running aground.
Jason Gedamke, ocean scientist of the Australian Antarctic Division in Tasmania, also shared that he first heard the sound, which he likened to a wielded light saber of the famous "Star Wars" anthology, while on a boat in Australian waters.
Scientists are stumped with a whale-like sound measured at 52 Hertz because whales usually vocalize between 17-18 Hertz.
The long search for the source of the noise pointed to the whales when researchers attached an HTI-96-MIN hydrophone, a device used for underwater sound recording, and tagged multi-sensor suction-cup tags to two Antarctic minke whales.
Interestingly, the strange sound was bestowed with various names from "Julia," which was coined by the NOAA because of the sensual sound it made, "Slow Down," a sound suspected to be made by an iceberg in 1997, to "the bio-duck," as coined in the study.