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