Scientists have at last discovered the elusive "bio-duck," and it isn't a bird at all. The creature making a quack-like sound in the Southern Ocean is actually the Antarctic minke whale, Live Science reported.

Researchers have been recording the unusual sound for decades, first capturing the low-pitched pulses in the 1960s. Due to the repetitive quality of the "quacks," which come about every 3 seconds, scientists thought the sounds could be coming from a submarine.

After years of research, a group of scientists detailed the connection between the minke whale and the "bio-duck" sound in the journal Biology Letters.

Because they have tied the whale species to the duck-like sound picked up on recordings, scientists can now track the animal's movements, numbers and behavior.

The researchers inadvertently discovered that minke whales make the sound when they were observing the animal's feeding habits and movements.

A group from NOAA Northeast Fisheries Science Center in Woods Hole, Mass., tagged two Antarctica minke whales in February 2013 to observe their behavior.

Denise Risch, a marine biologist at NOAA and lead study author, later analyzed acoustic recordings picked up by underwater microphones on the tags to reveal the quack-like sounds.

The unique noises "can now be attributed unequivocally to the Antarctic minke whale," Risch and her colleagues wrote in the study.

Further mysteries to be solved include how whales use the sound as well as whether or not both male and female minke whales make the repetitive, low-pitched noises. Risch has hypothesized that the "quacks" are intended to help in breeding or navigating the ocean.

For now, the recorded sounds will help researchers learn more about minke whale behavior and track the animals even during winter weather conditions.

"The fantastic thing about acoustics is you can go back in time," said Risch, as quoted by Live Science.

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