‘We’d never heard anything like it,’ say scientists.
Two years ago, in the waters of the Mariana Trench – the deepest and darkest place on Earth – a mysterious sound was recorded that was unlike any ever heard. The three-and-a-half-second audio clip was of an eerie sort of lowing, ending in a metallic squeak.
The researchers who sent down the autonomous seafaring robot that recorded the call have spent the past few years trying to figure out what on earth could have made such a weird sound.
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After much speculation, a team from Oregon State University has tentatively identified the otherworldly sound. They assert that its source is almost certainly biological and suggest that it could be a new type of baleen whale call. They’ve rejected one theory that suggested that the sound was simply noise from a ship.
‘The sounds reported here are not similar to known anthropogenic sources such as noise produced by ships or seismic air guns. They also do not resemble geophysical sources, such as the very low-frequency sounds produced by earthquakes and ice, nor the sounds produced by wind or rain. We hypothesise that these complex sounds were produced by a biological source,’ says one of the team, Sharon Nieukirk.
The curious call, which spans frequencies between 38 and 8,000 hertz – well within the range of human hearing – has been nicknamed the ‘Western Pacific Biotwang’ and has been attributed to dwarf minke whales. Nieukurk’s team were fortunate to have an important clue in identifying the sound: another similar recording made in Australia’s Great Barrier Reef in 2001.
This, the ‘Star Wars’ recording as it became known, was discovered to be the cry of a dwarf minke whale. Based on similarities in frequency and structure between the two recordings, it seems likely that the Western Pacific Biotwang comes from the same species, or subspecies, of animal.
But that doesn’t mean the mystery has been solved altogether. Baleen whale calls are usually only heard during the mating season, which is in winter, as individuals try to attract mates. However, the Western Pacific Biotwang was recorded on a number of occasions during autumn 2014 and spring 2015. Scientists are still scratching their heads trying to figure out why the animals are singing all year round. The intrigue endures.