Strange Sounds Recorded In Mariana Trench Could Be New Whale Species

Strange sounds in the Mariana Trench most closely resemble those made by the Dwarf Minke Whale shown here, but may be from an unknown species. Joanne Weston/Shutterstock

Exploratory missions to the Mariana Trench in 2014 and 2015 picked up a haunting sound. An analysis of these recordings has led to the conclusion they came from baleen whales, having ruled out both geophysical and human-produced sounds. Although these calls most closely resemble the sounds made by minke whales, they are so different from anything we have heard before they may come from an unknown species.

As the deepest part of the ocean, the Mariana Trench has attracted considerable research attention. From September to November 2014, and again from March to April the following year, Seagliders explored the part of the trench designated a Marine National Monument. Detectors on the gliders picked up frequent mysterious sounds they dubbed the “Western Pacific Biotwang”.

In The Journal of the Acoustical Society of America, a paper by Sharon Nieukirk of Oregon State University and colleagues proposes the source of these sounds came from a baleen whale. One explanation is that the sounds represent a local dialect of minke song, but a more interesting theory is that there is a species of whale out there we've never seen.

Such a claim might seem unlikely at first to non-whale experts. It's one thing to discover a new species of insect now and then, but aren't whales a little large to overlook? Huge as whales are, they can still get missed in the vastness of the ocean, particularly species that rarely come near land. The signal of one previously unknown whale species was detected last year, and this year a whale skeleton in Alaska was reported as probably being from an undescribed species.

Locations where the biotwang was detected. Nieukirk et al/The Journal of the Acoustical Society of America

A whale that prefers the deep waters of the Trench would be particularly likely to evade our notice.

The Biotwang lasts between 2.5 and 3.5 seconds, into which its maker packs five components, including moans at frequencies of 38 hertz (about double the lowest notes humans can hear). It finishes with a metallic-sounding pulse that can reach frequencies of 8000 Hz.

“It’s very distinct, with all these crazy parts,” Nieukirk said in a statement. “The low-frequency moaning part is typical of baleen whales, and it’s that kind of twangy sound that makes it really unique. We don’t find many new baleen whale calls.” 

The closest recorded relative of the biotwang is a "ba-ba-boinnnggg" noise given off by dwarf minke whales around the Great Barrier Reef, dubbed the “Star Wars” call for its resemblance to the sounds of blasters in the films. Since dwarf minkes in the northern Pacific make a very different sound it is possible the biotwang is a further example of their vocal diversity, but Nieukirk also leaves open the possibility of an entirely new species. She hopes researchers who have detected something similar will recognize the parallels and combine the knowledge.

Assuming the whales are not just enjoying messing with the silly humans' heads, the reason for the call is also unknown. “If it’s a mating call, why are we getting it year round? That’s a mystery,” Nieukirk added.

Given the diversity of whale sounds, Dory really didn't stand a chance of successful communication.

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