A mysterious sound recorded near the Mariana Trench might be a newly discovered whale call.
Researchers who documented the vocalization are calling it the “Western Pacific Biotwang.” The call—which has a range that goes from as low as 38 hertz to as high as 8,000 hertz—is thought to be from a minke whale, a type of baleen whale.
“It’s very distinct, with all these crazy parts,” Sharon Nieukirk, senior faculty research assistant in marine bioacoustics at Oregon State University, 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.”
Nieukirk and her team used “passive acoustic ocean gliders”—a type of autonomous nautical robots that can dive up to 3,280 feet (1,000 meters) underwater—to record the sounds. The “Western Pacific Biotwang” data was discovered in fall 2014 and spring 2015. The robots dove into the Pacific Ocean east of Guam near the Mariana trench, which is the deepest part of the ocean.
The five-part call lasts up to 3.5 seconds. They have many recordings of the sound—which Nieukirk and her team suspect is from a minke whale. The researchers hope that publishing their work in the Journal of the Acoustical Society of America will lead to an exact identification.
The complexities of the call and the range of the frequencies led researchers to compare it to calls from a group of dwarf minke whales off the northeast coast of Australia. They note that there are several types of minke whales in the area, but they do not have much information about their sounds or behavior.
“We don’t really know that much about minke whale distribution at low latitudes,” Nieukirk said. “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.”
Most baleen whales have seasonal calls for breeding and feeding. The new call seems to occur year-round, leading researchers to believe that it may serve a complex function that needs to be translated.
The call still needs to be translated. Most baleen whales use specific vocalizations for seasonal breeding and feeding, but this call — since it seems to occur all year — may have a complex function, the researchers said.
“If it’s a mating call, why are we getting it year-round? That’s a mystery,” Nieukirk said. “We need to determine how often the call occurs in summer versus winter, and how widely this call is really distributed.”
