Western Pacific Biotwang

The Western Pacific Biotwang is an underwater sound first detected in October 2014 by autonomous underwater hydrophone gliders near the Mariana Trench, and which has been identified as a vocalization produced by Bryde's whales (Balaenoptera edeni).[1][2][3] This unique sound, described as a low, sonorous grunting followed by a squeaky, mechanical echo, puzzled researchers for years due to its unusual characteristics that didn't immediately align with known whale calls.[1]

Initial theories suggested the biotwang was made by baleen whales, given its low-frequency components, but its distinct "twangy" and metallic high-frequency elements made it difficult to pinpoint a specific species.[1] [4]

It starts with low moan of 38 Hz, typical of baleen whales, then followed by a highly synthetic sounding twangy noise of 8,000 Hz, which is what makes this sound so unique. Researchers at Oregon State University, who first recorded the sound, gave it the name we know it as and noted its resemblance to the "Star Wars" call produced by dwarf minke whales.[4][5] However, the consistent year-round detection of the sound, unlike typical seasonal mating calls of baleen whales, added to the mystery.[4]

The breakthrough in identifying the source came through a combination of visual and acoustic surveys conducted by NOAA scientists in the Mariana Archipelago.[1][2][6] During a survey in 2018, researchers observed Bryde's whales on ten occasions, and on nine of those instances, the distinctive biotwang sound was simultaneously recorded.[1][2][3] This strong correlation provided compelling evidence linking the sound to Bryde's whales.[1][3]

To further confirm this, scientists utilized advanced AI tools, developed in collaboration with Google, to analyze vast amounts of historical acoustic data.[1][2][6] These tools transformed audio data into spectrograms and trained algorithms to identify the specific frequencies of the biotwang, allowing for rapid analysis of over 200,000 hours of recordings.[1][2][6] This AI-powered analysis confirmed the consistent seasonal presence of biotwangs primarily in the Mariana Archipelago and near Wake Island, suggesting that the call is specific to a western North Pacific population of Bryde's whales.[2][6][7]

The study also revealed that the occurrence of biotwangs varied year to year, with a significant increase observed in 2016 during a strong El Niño event, and almost none during a La Niña year in 2021.[1][2][6] This suggests that the whales' movements and vocalizations may be influenced by environmental conditions and the distribution of their prey, such as krill, sardines, and anchovies.[1] While the exact purpose of the biotwang remains under investigation, researchers hypothesize it could serve as a contact call, a form of "Marco Polo" in the ocean, helping whales locate each other.[3] The identification of the biotwang's source provides valuable insights into the distribution and migration patterns of this elusive Bryde's whale population, aiding in their conservation efforts under the Marine Mammal Protection Act.[2][6]

See also

References

  1. ^ a b c d e f g h i j Hobson, Melissa (2024-12-01). "Hear the Mysterious Deep-Ocean Sound Called 'Biotwang' that Scientists Have Finally Identified". Scientific American. Retrieved 2025-09-08.
  2. ^ a b c d e f g h Fisheries, NOAA (2024-09-19). "Bryde's Whales Produce Biotwang Calls, Which Occur Seasonally in Long-Term Acoustic Recordings From the Central and Western North Pacific | NOAA Fisheries". NOAA. Retrieved 2025-09-08.
  3. ^ a b c d Baker, Harry (2024-09-19). "Creepy 'biotwang' noises coming from the Mariana Trench finally explained after 10 years". Live Science. Retrieved 2025-09-08.
  4. ^ a b c "New, complex call recorded in Mariana Trench believed to be from baleen whale". phys.org. 14 December 2016. Retrieved 8 September 2025.
  5. ^ "Scientists Finally Solve Mystery of Weird Mariana Trench Sound". HowStuffWorks. 2016-12-23. Retrieved 2025-09-08.
  6. ^ a b c d e f Fisheries, NOAA (2024-10-21). "Hey, Google: Find this New Whale Sound | NOAA Fisheries". NOAA. Retrieved 2025-09-08.
  7. ^ Starr, Michelle (2024-09-25). "Deep Ocean Sound Confused Scientists For Years. We Finally Know What Makes It". ScienceAlert. Retrieved 2025-09-08.
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