Wildlife

What’s Making Duck Sounds in the Ocean? Mystery Solved

It may sound quacky, but mysterious duck-like sounds in the oceans are made by whales, a new study says.

Scientists have been trying to decode the perplexing low-frequency sounds, which occur every winter in the Southern Hemisphere in the ocean around Antarctica, since sonar began detecting them in the 1960s.

An Antarctic minke whale swims near Boothe Island in the Lemaire Channel, Antarctica. Photograph by Paul Souders, Corbis

“’Bio-duck’ was actually a fitting description for the sound. It really does sound a lot like a duck,” said study leader Denise Risch, a marine acoustic specialist at the U.S. National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center. (Listen to the bio-duck sounds.)

The noise was so deep and repeated so regularly that at first, researchers weren’t even sure that a living creature could be producing the noise.

Some scientists hypothesized that ‘bio-duck’ might be produced by ultra-high-tech military devices at the bottom of the ocean. As time passed, however, more and more evidence mounted that bio-duck was actually produced by a deep-sea animal: The noise appeared each October and then disappeared by the end of December, and it was found only in a limited area near Antarctica; both of these factors indicated a migrating animal. The question was, which one? (Learn more about our noisy oceans.)

Now, analysis of calls between Antarctic minke whales (Balaenoptera bonaerensis) reveal the marine mammals were the source of the sound.

“It was very exciting. When going through the recordings, my heart jumped a little bit when I found a sound that was a good candidate for the signal,” said Risch, whose study appeared April 22 in the journal Biology Letters.

Decoding Bio-Duck 

Only a truly massive marine animal could produce a sound like that, Risch reasoned.

So when a group of scientists asked her to analyze acoustic data from Antarctic minke whales, Risch leaped at the chance to investigate what she believed might be the source of bio-duck.

Antarctic minke whales, which weigh between six and nine tons and measure about 25 to 35 feet (7 to 11 meters), use baleen to filter out krill and other small marine animals from the frigid waters off Antarctica. (See National Geographic’s whale pictures.)

The animals spend their winters in the warmer waters nearer the tropics and return to Antarctic waters to breed during the summer. Like many marine mammals, Antarctic minke whales were believed to communicate by calling to each other beneath the waves. However, none of these whales’ calls had been formally recorded and analyzed.

So in 2013, Risch and colleagues took a boat into Wilhelmina Bay, off the western Antarctic Peninsula, and used a handheld pole to attach sound recorders to two wild minke whales. (See your Antarctic pictures.)

These acoustic devices, which were attached by specialized suction cups and stayed on for several hours, recorded all of the animals’ calls before detaching and falling to the bottom of the ocean. The devices sent out a signal that told the researchers where to go to retrieve them.

Risch obtained 8 hours of data from one whale and 18 hours from another. Most of the calls were downsweeps, or short bursts of sound that start off at a higher frequency and rapidly fall to a lower one. (See “Hear the Surprising Sounds of Ocean Life.”)

But from each whale, Risch was able to identify several bio-duck calls that were distinct from the other calls. Other acoustic experts on her team agreed: The Antarctic minke whale was the source of bio-duck.

More Mysteries

The team has solved the major mystery of bio-duck, but plenty are left for them and other scientists to uncover.

For instance, no one knows the purpose of bio-duck calls or how the whales use them to communicate with each other.

Nor does Risch have any idea why bio-duck is used only at the height of the southern summer and not at other times of the year.

But for now, Risch is happy to have solved an ocean enigma. “It was a great discovery,” she said.

Follow Carrie Arnold on Twitter and Google+.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at http://www.carriearnold.com
  • Cher

    Amazing!!! Definitely not something the Japanese “Scientific” Whalers would ever learn from killing them!!! So exciting to learn about this new discovery!!!

  • Katerina Waligora

    You guys need to supply them with Rosseta Stone CD

  • Rene

    If its a parent calling to a baby…humans us motherse…If whales do this its for bonding and warning of danger.
    Iceburgs, preditors as children grow they have this info in their repitoire. What is whales us some sounds like radar in submarines that bounce back to tell them info like depth, speed, and distance between them and another object such as an iceburg or predator, ships…which reflexs relationship to its size. Where to find food or where the warm currents or currents are in the ocean. When to go up for air and maybe their singing lullabyes sometimes. or recounting shories like generations do of ancient times/ancestory, ways for their young to know to return to the Artic to breed.

  • muhammad farikh

    maybe all of cetacea making duck sound with different models ? its so dizzy

  • Hari

    Wider thoughts Rene , ya perhaps ur true .. so much to learn and find about the animals we share this mother earth .. hope we don’t delay to know their mysterious world before its too late

  • Rimpa

    Cher, atleast the japanese kills them for food…while Americans kill humans for nothing.

  • Allana Clark

    Ah but Rimpa, there are far too many humans and far too few Minke whales…

  • Stanley

    Great! Now solve the “Bloop”!

  • ANIL KALANGOT MANGOOL

    THERE IS A VAST LOT MORE TO BE LEARNED ABOUT THESE GREAT ANIMALS ENRICHING OURSELVES IN THE PROCESS BUT ARE WE DOING ENOUGH.

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