A New Population of Blue Whales Was Discovered Hiding in the Indian Ocean

On an undated photo of the Environment Society of Oman, a blue whale in the Indian Ocean. (Robert Baldwin / Environmental Society of Oman via the New York Times)
Weighing up to 380,000 pounds and about 30 meters long, the blue whale - the largest creature to ever live on earth - seems difficult for human eyes and ears to miss at first.
But a previously unknown population of Leviathans has lurked in the Indian Ocean for a long time, leaving scientists no smarter, new research shows.
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The covert roster of whales, described in an article published last week in Endangered Species Research magazine, has its own anthem: a slow, roaring ballad that is different from any other whale song ever described. It connects only about a dozen other documented blue whale songs, each of which is the calling card of a unique population.
"It's like listening to different songs within a genre - Stevie Ray Vaughan versus B. B. King," said Salvatore Cerchio, marine mammal biologist with the African Aquatic Conservation Fund in Massachusetts and lead author of the study. "It's all blues, but you know the different styles."
The find is "a great reminder that our oceans are still a very unexplored place," said Asha de Vos, a marine biologist who studied blue whales in the Indian Ocean but was not involved in the new study.
Cerchio and his colleagues prepared for the newly discovered song of the whales off the coast of Madagascar a few years ago when they were scientifically tracking a pod from Omura's whales. After hearing the rumble of blue whales through a recorder planted in the coastal shelf, the researchers decided to drop their instruments into deeper water in hopes of continuing to listen.
"If you place a hydrophone somewhere where no one has placed a hydrophone before, you will discover something," said Cerchio.
A number of blue whale populations, each with their own distinctive croon, have long been known to visit this pocket of the Indian Ocean, Cerchio said. But one of the songs that crackled through the team's Madagascar recordings was unlike any the researchers had heard.
By 2018, the team had picked up several more cases of the new whales' now recognizable refrain. Partnerships with other researchers soon revealed that the distinctive calls were detected at another outpost off the coast of Oman in the Arabian Sea, where the noises appear to be particularly frequent. Another stroke of luck came later that year when Cerchio learned that colleagues in Australia heard the whales sing the same song in the central Indian Ocean near the Chagos Archipelago.
The data from the three locations, each hundreds or thousands of kilometers apart, drew a rough portrait of a pod of whales that buzzed around the northwestern Indian Ocean and possibly beyond.
Using acoustic data to identify a new population is inherently indirect, like dusting fingerprints on the scene. But Alex Carbaugh-Rutland, who studies blue whales at Texas A&M University and was not involved in the study, said the results were "very solid, no pun intended".
The researchers ruled out the possibility that the songs could be attributed to other whale species. And comparisons of the new blue whale tune with others convincingly showed that the strain was different in the northwestern Indian Ocean, Carbaugh-Rutland said. "I think the evidence is really convincing," he said, making a comparison with linguistic dialects.
Genetic testing would help clear the case, he added. But blue whales, which spend most of their time far from shore, are difficult to study. Whaling in the 19th and 20th centuries also removed hundreds of thousands from their ranks; It is estimated that 10,000 to 25,000 blue whales will remain.
Not much is known about blue whale songs, although most researchers believe they help men woo their partners, as is the case with closely related species. That can lead to changes to a cetacean tune being quite high, said de Vos: "If two populations cannot talk to each other over time, they will grow apart."
Finally, populations with different attitudes to a tune could break up into subspecies with their own behaviors and quirks. There is no evidence yet that this has happened to these blue whales, nor much information about what may have separated them from their southern relatives. But even if the whales in this new group have not yet occupied a new branch on the tree of life, it is worth getting to know them.
"What shows us is that there are different populations with different adaptations and potentially different needs," said de Vos. To protect the world's blue whales, she said, "There isn't a single protection measure that will work."
This article originally appeared in the New York Times.
© 2020 The New York Times Company

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