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Scientists Discover a New Population of Blue Whales by Their Unique Song

They first heard the 'previously unreported' song in 2017, leading to the discovery of a new population that’s been hiding in the Indian Ocean.
January 5, 2021, 9:02am
blue whale
Photo: Elianne Dipp, courtesy of Pexels

The ocean is unimaginably vast, so much so that only five percent of the Earth’s oceans have been explored and charted by humans. Now, in another surprising discovery, a new population of blue whales—the largest creature to have ever lived on Earth—has been found in the western Indian Ocean for the first time ever. According to NOAA, these whales weigh over 330,000 pounds and grow up to 110 feet long.

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What sets these gentle giants apart is that they sing a different tune, quite literally. According to the study published in Endangered Species Research, the song of these whales is “previously unreported”, hinting that the recently discovered population might be unique from the two or three known subspecies of blue whales in the Indian Ocean. Each population boasts of a unique song.

Dr. Salvatore Cerchio, director of the African Aquatic Conservation Fund’s Cetacean Program and Visiting Scientist at the New England Aquarium (NEAQ), led the analysis of the recordings that led to the discovery.

“It's like hearing different songs within a genre – Stevie Ray Vaughan versus B. B. King,” Cerchio told The New York Times. "It's all blues, but you know the different styles.”

Scientists discovered this new population by accident when they overheard their song. The song, that’s unlike any other, joins only a dozen or so of whale songs previously recorded. The unique song type implies the probable existence of a whale population that has been undetected or conflated with another population. 

The same whale song was recorded from three spots around the Indian Ocean, each separated by hundreds or thousands of miles, and enabled the scientists to chart a map of the whales’ unique locations, and delve deeper into the history of the population. According to the study, “the novel song-type was recorded off Oman in the northern Indian Ocean/Arabian Sea, off the western Chagos Archipelago in the equatorial central Indian Ocean, and off Madagascar in the southwestern Indian Ocean.” 

Being the only whale song to have been heard in the western Arabian Sea, scientists have dubbed it the “Northwest Indian Ocean” song-type to distinguish it from other regional song-types. 

In 2017, while on a quest to document a different species of the rare Omura whales, Cerchio first recorded the novel song in the Mozambique Channel off Madagascar, and again while analysing a set of recordings collected off the coast of Oman. In 2018, the team reported their findings to the Scientific Committee of the International Whaling Commission (IWC), which was then attempting to evaluate the status of blue whale populations in the Indian Ocean. In the same year, these findings were validated by another team led by Emmanuelle Leroy and Tracey Rogers of the University of New South Wales, in Sydney, Australia. Upon reading the IWC report on the new song, Leroy recognised that they also had recorded the same song off the Chagos Archipelago.

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“It was quite remarkable to find a whale song in your data that was completely unique, never before reported, and recognise it as a blue whale,” Cerchio said in a press release by NEAQ. “With all that work on blue whale songs, to think there was a population out there that no one knew about until 2017, well, it kind of blows your mind.”

Each new discovery connected to blue whales serves as a harbinger of hope for the species’ sustained recovery after having been hunted to near extinction across the globe in the 20th century. Only recently have the populations started to recover, following worldwide efforts and the 1986 IWC ban on commercial whaling. A report by Forbes estimated that blue whale populations dropped from 350,000 at the turn of the 20th century to between 10,000 to 25,000 today. These numbers reveal the gravity of the situation, which is why the species remains critically endangered. 

The scientists said that the timing of the population’s presence off Oman suggests they might have been survivors of intense historic whaling. The illegal Soviet Union whaling that took 1,294 blue whales in the 1960s is likely to have targeted this population. Based on an analysis of the Soviet catch data, the study suggests, “If there is a northern Indian Ocean subspecies... it is likely this population.”

The discovery of the previously undetected song-type and the fact that even the largest creature on Earth could be so easily overlooked has convinced the scientists that the population is small and thus “in critical need of status assessment and conservation action.”

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