Being able to exceed thirty meters in length and weigh nearly 170 tons, blue whales are the largest creatures to have lived on Earth. With such measurements, it’s hard to imagine that an entire population could go unnoticed for so many years. And yet.
All blue whales sing low notes, but we know that each population has its own scores. In one article recently published, researchers describe a new song that can be heard from the Arabian Sea in southwest India, to the Chagos Archipelago and south of Madagascar, in southwestern India. Indian Ocean.
An unknown population
Dr Salvatore Cerchio, director of the cetacean program of the African Fund for Aquatic and Scientific Conservation, recorded this song for the first time in 2017. He was then conducting research focused on whales in Omura, in the Mozambique Channel. off Madagascar. The ballad was slow, howling, and distinct from any other whale song ever described.
Cerchio was also working with a team collecting acoustic recordings off the coast of Oman, as part of a research effort focused on the endangered Arabian Sea humpback whale. When analyzing acoustic data from Oman, the team recognized the same unusual song. The researchers therefore wondered, suggesting that these notes could be the work of an unknown population of blue whales evolving in the western Indian Ocean.
Then, the following year, the team reported their findings to the scientific committee of the International Whaling Commission (IWC), then in the process of assessing the state of blue whale populations in the Indian Ocean. Biologists Emmanuelle Leroy and Tracey Rogers, of the University of New South Wales, Sydney (Australia) were then surprised to find that this song also corresponded to those they had recorded a few months earlier off the coast of the Chagos Archipelago, in the central Indian Ocean.
In other words, three different teams of researchers had recorded the same notes on three different sites. This discovery therefore aroused a lot of enthusiasm and raised many questions about the movements of these whales, which obviously represent a whole new population.
“Very solid” results
Of course, identifying a new population of blue whales by acoustic data alone might seem rushed. Alex Carbaugh-Rutland, who studies blue whales at Texas A&M University, pointed out, however, that these results “were very solid“.
Genetic samples could be used to certify it. However, this work will still take some time since these large mammals spend most of their time on the high seas. Whaling, carried out in the 19th and 20th centuries, also wiped out hundreds of thousands of these animals. It is estimated that there are still between 10,000 and 25,000 in the world today.
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