Researchers Inch Closer to Solving the Mystery Behind ‘Quacking Caller’ in the Southern Ocean
In July 1982, some researchers from New Zealand plunged into the depths of the Southern Ocean to map out its soundscape in a first-of-its-kind project. At some point during their voyage, their instruments detected a mysterious sequence of sounds that resembled the quacks of a duck. Despite a coterie of investigations, the source of this sound remained a mystery. It wasn’t until February 2013 that researchers once again dived into the waters of the Southern Ocean and tagged minke whales. The sounds produced by these whales appeared to match, to a great extent, the mysterious duck sound. In 2014, researchers published a paper in the Royal Society journal Biology Letters, documenting the entire episode.
Dubbed “Bio-Duck sound,” the mysterious sound detected in the 1980s consisted of a series of pulses with a 3.1-second interval between two series, according to the 2014 report in Science Magazine. The sequence and pattern of this sound sent the concerned scientists’ brains jostling in a puzzling mode. “The sound was so repeatable, we couldn’t believe at first that it was biological,” said lead researcher Ross Chapman from the University of Victoria, in a press release by the Acoustical Society of America. He added that his fellow researchers had recorded similar sounds in regions around Australia as well. After elaborate analysis, he concluded that the source of this sound was, most likely, biological.
Which animal was making the sound wasn’t confirmed. It could be the minke whales, as previously assumed. But irrespective of the animal, the sound offered a fascinating window into the understanding of oceans and their soundscapes. Chapman had been involved in studying the sounds of the ocean since the 1980s. But despite such an extensive experience, the mystery of this “quacking caller” in the waters of the Southern Ocean kept him awake in the night. “I became involved in the analysis of the data from the experiment in 1986,” Chapman said. “We discovered that the data contained a gold mine of new information about many kinds of sound in the ocean, including sounds from marine mammals.”
“We learned something new about sound in the ocean every day as we looked further into the data—it was really an exciting time for us,” he said. In November 2024, he presented the work analyzing this sound mystery as part of the virtual 187th Meeting of the Acoustical Society of America. The “acoustic identification” of the sound-making creature offers an exciting opportunity to researchers to retrospectively analyse several years’ worth of existing long-term recordings to explore seasonal occurrence, migration patterns, and the possibilities of using acoustics to estimate ocean abundance, they wrote in Science.
Chapman thinks that it could also be a conversation. The data he recorded came from the acoustic antenna attached behind a ship. These antennae allowed him to detect the direction from which the sound was coming. In this case, the direction seemed to be blurry, which made him think that the sound could be a conversation and not just a call. “It’s always been an unanswered issue in my mind,” Chapman said. “Maybe they were talking about dinner, maybe it was parents talking to children, or maybe they were simply commenting on that crazy ship that kept going back and forth towing that long string behind it.”
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