For years, a mysterious sound emanating from the depths of the Mariana Trench, the world’s deepest ocean trench, has puzzled scientists. Dubbed ‘biotwang,’ this odd noise, described as a combination of low rumbles and high-pitched metallic ringing, sounded remarkably like the noises made by spaceships in science fiction films. Now, after years of investigation, researchers have finally cracked the code.
The source of these intriguing sounds? Bryde’s whales (Balaenoptera edeni), a species of baleen whale. Scientists first detected the biotwang noises in 2014 using underwater gliders to survey the Mariana Trench. However, it took years of meticulous research and the aid of advanced artificial intelligence (AI) to pinpoint the origin of these calls.
The breakthrough came in 2016 when researchers revealed that biotwang was likely a call from a large baleen whale, but the specific species remained a mystery. Researchers strongly suspected Bryde’s whales were the culprits when they observed 10 of these cetaceans swimming near the Mariana Islands and recorded nine of them making the distinctive biotwang noise. To confirm their suspicions, the team meticulously analyzed years of audio recordings captured by monitoring stations across the Mariana Archipelago, looking for a correlation between the biotwang noises and the whale’s migration patterns.
They used AI to transform the biotwang into images, known as spectrograms, that could be easily differentiated from other sounds by a machine learning algorithm. The study also found that biotwang was only heard in the northwest Pacific, despite Bryde’s whales being found in a much wider area, suggesting that only a specific population of the whales is making this unique sound.
The data also revealed a spike in biotwang noises during 2016, coinciding with a rise in ocean temperatures caused by an El Niño event, which brought a greater number of Bryde’s whales to the area. While the exact purpose of the biotwang calls remains unknown, scientists suspect they might be used for communication.
“It’s possible that they use the biotwang as a contact call, a sort of ‘Marco Polo’ of the ocean,” says Ann Allen, lead author of the study and an oceanographer at NOAA’s Pacific Islands Fisheries Science Center. “But we need more information before we can say for sure.” This discovery sheds light on the incredible and often hidden world of underwater communication, reminding us of the mysteries that still lie in the depths of our oceans.
