The mystery of what is making a loud quacking noise in the ocean - which has puzzled scientists for decades - has been solved, researchers claim. Apparently it's the Antarctic minke whale and not, as you might have assumed, a giant duck.
The bizarre, repetitive sound, known as the "bio-duck", was first recorded in the Southern Ocean by submarine sonar operators five decades ago. But until now, scientists haven't been able to pin down what was actually making the noise.
The answer comes in a paper published in the Royal Society journal Biology Letters.
Here's a recording of the bio-duck sound from the paper:
As you can hear, it doesn't sound anything like a duck, but does sound quite a lot like bass-heavy ambient electronica.
The team behind the paper, led by researcher Denise Risch, got their "conclusive proof" that it was Antarctic minke whales quacking by attaching "multi-sensor acoustic recording tags" to two of the minke whales. The paper says that the recordings - the first of their type ever made of minke whales - provided evidence that the quacking sounds could be "attributed unequivocally" to the whales.
However, the team adds that they still don't know exactly why the whales are quacking/producing bass-heavy ambient electronica.