Since 2014, scientists have listened to a unique whale vocalization they call a “biotwang.” The call, which sounds a bit like squeaking metal, was first detected by an autonomous sea glider near the Mariana Archipelago. In 2018, researchers realized that the sound came from groups of Bryde’s whales, baleen whales that thrive in warm oceans.
By Erin Blakemore
But where and when do Bryde’s whales make biotwangs? Long-term passive recording at the sea bottom had the potential to answer that question — if researchers could locate biotwang sounds among almost 200,000 hours of recordings.
So the National Oceanic and Atmospheric Administration used Google-developed tools in the hopes that artificial intelligence and machine learning might be able to sift through 500 terabytes of data.
It worked: The analysis identified biotwangs in sound data from the western North Pacific — and revealed a seasonal pattern in the vocalizations.
The majority of biotwangs were detected in waters off the Mariana Archipelago and nearby Wake Island, suggesting the calls are specific to a population of Bryde’s whales that pass through the area during twice-annual migrations between breeding and feeding grounds. Vocalizations peaked slightly in February and April, and spiked between August and November. More calls were detected during 2016’s El Niño, and calls declined during 2021’s La Niña, suggesting that ocean currents and oscillations affect the whales’ migratory patterns.
Writing in Frontiers in Marine Science, the researchers conclude the whales have a “complex range most likely linked to changing oceanographic conditions in this region.” As climate change accelerates, they write, they expect the whales’ migration patterns to shift poleward along with ocean currents — causing the whales to travel greater distances and work harder to obtain food.
“We now know that Bryde’s whales produce Biotwangs, and the geographical and seasonal patterns of the calls,” NOAA Fisheries said in a news release. “This gives our scientists a better idea of their population distribution and movement pattern, and will help us better protect this species.”
