Mysterious Mariana Trench sound identified as originating from a baleen whale

Passive acoustic ocean gliders, or underwater drones recorded mysterious sounds in the vicinity of the Mariana trench during expeditions in 2014 and 2015. The sounds were short, complex, and featured a moan with both harmonics and amplitude modulation. The frequency of the moans were known to go as low as 38 hertz that tended to end with a metallic sweep finale that went up to 8,000 hertz. The broad frequency range in the vocalisations were from a previously unknown source. http://bioacoustics.oregonstate.edu/sites/labs7/files/project-media/BioTwangExample_0.mp3 Researchers from Oregon State University’s (OSU) Hatfield Marine Science Center named the sound the “ Western Pacific Biotwang .” The mysterious sound emerged from the deepest place on the Earth, located midway between Japan and Australia. The researchers studied and analysed the sounds, and concluded that the sound was most likely the vocalisations of a baleen whale. If so, it is an entirely new type of vocalisation, and there are some mysteries still remaining to be answered. The purpose of the call is unknown, and it cannot be a mating call as it was heard all year round. Baleen whales are known as Mysticeti, include many species of whale including right whales, the gray whale, the fin whale, the blue whale and the humpback whale. The most likely candidate for the vocalisation has been identified as the minke whale, the smallest whale in the family. The results of the research have been published in the Journal of the Acoustical Society of America, however, the work of the scientists is not over. They intend to launch an expedition to confirm the source of the sound, using visual, acoustic, video and genetic data. Sharon Nieukirk, senior faculty research assistant in marine bioacoustics at Oregon State University, and lead author of the study says, “We don’t really know that much about minke whale distribution at low latitudes. The species is the smallest of the baleen whales, doesn’t spend much time at the surface, has an inconspicuous blow, and often lives in areas where high seas make sighting difficult. But they call frequently, making them good candidates for acoustic studies.” What the researchers have dubbed the “Western Pacific Biotwang” most closely resembles the “Star Wars” sound known to be produced by dwarf minke whales. The sound is similar to a lightsabre being activated. This is what the “Star Wars” call sounds like, courtesy of the University of California Santa Cruz : http://www1.ucsc.edu/currents/00-01/06-04/minke.wav Apart from the signature “Star Wars” sound of the dwarf minke whales, another known signature sound is called a “boing.” A recording of the “boing” sound is available at the Cetacean Sounds page maintained by the Southwest Fisheries Science Center. This is what the “boing” sounds like. https://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/Sounds/MinkWhaBoin.wav More information on dwarf minke whales and the sounds they make can be found at the Ocean Conservation Research page for the minke whale .