After more than 50 years of driving researchers crazy, the mysterious “quacking” sounds emanating from beneath Antarctic ice have been traced to minke whales. The “duck” noise, which is made up of repetitive low-pitched pulsing sounds has baffled scientists at the bottom of the world ever since it was first detected by a submarine back in the sixties.
"In the beginning, no one really knew what it was," said Denise Risch, a marine biologist at NOAA Northeast Fisheries Science Center in Woods Hole, MA. Because the sound was so repetitive, scientists first thought it might be human-made, possibly coming from submarines. As time went on, people suggested a fish may be making the sound, but it seemed too loud.”
She also noted that the sounds, which “resonate in sets spaced approximately 3.1 seconds apart, occur seasonally, and have been heard simultaneously in the Eastern Weddell Sea off Antarctica and Western Australia.”
Now that the source has been identified, the decades of recordings will allow scientists to disseminate a wealth of information about the whales’ behavior. "The fantastic thing about acoustics is you can go back in time," Risch said.
Risch's colleagues tagged two Antarctic minke whales off of Western Antarctica with suction-cup tags that contained underwater microphones in order to learn more about their movements and feeding habits. To their surprise, they found that minkes were the source of the strange sounds. Now that the source has been identified, the decades of recordings will allow scientists to disseminate a wealth of information about the whales’ behavior, particularly during the Antarctic winter, when it is impossible to track them visibly.
Readers interested in learning more about Risch’s study can view her report in the April 22nd issue of the journal Biology Letters.