Researchers involved in the mission described their discovery in the Indian Ocean as a “conservation success”. Over the past decade, blue whales have been repeatedly captured in the area: According to researchers, in the 1960s, a Soviet whaling fleet killed hundreds of the creatures, and over the decades, 12,000 dwarf blue whales have been captured in the waters. As a result, their stocks were drastically decimated.
“It turns out that animals can recover if you stop killing them en masse and give them a chance to recover,” said Kate Stafford, lead researcher on the mission, cited by the BBC.
Commercial whaling, which peaked in the first half of the 20th century, has reduced global blue whale populations to a minimum. In 1926, the number of adult animals was estimated at 140,000. According to the International Union for Conservation of Nature and Natural Resources (IUCN), which, among other things, compiles the Red List of Endangered Species, there were between 5,000 and 15,000 adult blue whales in the world, according to most recent estimates from 2018. . The IUCN has classified the blue whale as an endangered species.
Portal/Sergio Canobbio According to researchers, blue whales roam the paradise island of Seychelles
Researchers listened to ocean sounds
“It’s the biggest animal that’s ever existed on the planet,” Stafford said. According to her, knowing that there is a population in the Seychelles is “incredibly exciting”. The discovery was published in the Journal of Endangered Species Research. It is based on recordings made with a sound machine on the seabed near the small island state.
The device was equipped with underwater microphones, batteries and recording devices and recorded 15 minutes of every hour at the site, every day, for a year. Stafford also kept a hydrophone – an underwater microphone – in the ocean for hours every day during a months-long expedition.
Balaenoptera musculus
is the scientific name for the blue whale. It occurs in all oceans except the Arctic Ocean. It can grow up to 30 meters long and weigh up to 150 tons.
First disappointment, then euphoria
“We heard remarkable things: the sound of sperm whales thousands of meters deep and dolphins locating echoes and communicating – but unfortunately no blue whales,” said sound engineer Chris Watson, who was part of the expedition.
However, after scientists recovered the device from the seabed and analyzed its recordings, they discovered that blue whales were actually traveling through the region and communicating with each other in the researchers’ absence. The characteristic call of mammals, of very low frequency, was heard mainly in March and April.
The Seychelles could be “really important” for blue whales, Stafford said of the discovery. The reason: Blue whales “sing during breeding season and based on what we know about whales, we think it’s probably the males that sing.” .
WWF: Nine different known songs
The experts were also able to discover which acoustic population the blue whales in the region belong to. “You can tell them apart by the noises they make,” Stafford said. She attributes blue whales to the acoustic population generally associated with the northern Indian Ocean.
“Nine different blue whale songs are known worldwide, each of which is sung by the animals of a specific region, four of which are in the Pacific, three in the Indian Ocean, one in the Atlantic and one in the Southern Ocean,” he writes. the environmental protection organization WWF. “Some songs haven’t changed in over thirty years. The functions of whale song have not yet been conclusively clarified. In any case, they serve to facilitate interaction between individuals.”
According to WWF, blue whales produce the most powerful sounds in the entire animal kingdom: “They can reach 188 decibels, exceeding the volume of a jet plane (140 decibels). Furthermore, blue whales emit sounds at the lowest frequency compared to other animals.” Due to the good sound conductivity of water, the sounds of blue whales can be heard over hundreds and even thousands of kilometers.
Seychelles protects 400 thousand square kilometers of sea
Experts want to take a closer look at the Seychelles’ role for blue whales. An area around the islands was officially protected in a unique “debt-for-nature swap” that allowed the country to write off almost €19.3 million of its national debt in exchange for doing more to protect its oceans. Around 400,000 square kilometers of its seas are now protected.
Protection against noise pollution is also a major concern. “There isn’t a lot of ship traffic in the Seychelles, so perhaps we could imagine the area as a nice, peaceful and safe place for blue whales,” said Stafford.