Ocean giants are second only to blue whales in length, with slender bodies that help them glide through the water at great speed. They were unable to escape industrial whaling, however, and were slaughtered to near extinction during the 20th century as hunters systematically decimated whale populations across the planet. “They were reduced to 1 or 2% of their original population size,” said Helena Herr, from the University of Hamburg, lead author of the study, published in the journal Scientific Reports. “We’re talking about a few thousand animals left for the entire southern hemisphere.” While scientists say southern fin whale numbers are slowly recovering after whaling was banned in 1976, there have been few sightings of these mysterious animals in large groups in their historic feeding grounds. But in scenes Herr described as “one of nature’s greatest events”, researchers and filmmakers were able to capture footage of up to 150 southern fin whales in the Antarctic. Drone footage, taken by wildlife filmmakers from the BBC, shows the fin whales swooping and hunting through the water, releasing large blasts of air as they surface, as the birds circle in the sky above them. “The water around us was boiling because the animals kept coming up,” Herr said Thursday. “It was exciting, just standing there and watching it.” Humpback whales in the “exciting” spectacle of Antarctica. Photo: Helena Herr/University of Hamburg/AFP/Getty Images On two expeditions in 2018 and 2019, the researchers recorded 100 groups of fin whales, ranging from small gatherings of a few individuals to eight huge gatherings of up to 150 animals. Previously, recorded feeding groups had a maximum of about a dozen whales. Using data from their surveys, the authors estimate that there could be as many as 8,000 fin whales in the Antarctic region. Fin whales can live to be about 70 or 80 years old when left alone and have only one calf at a time, so Herr said recovering populations has been a slow process. He said the growing number of southern fin whales was an encouraging sign that conservation measures could be working, although he noted other threats, including being struck by boats. The International Union for Conservation of Nature now ranks fin whales as “vulnerable” and estimates the global population at 100,000, with most of them in the northern hemisphere. More whales could also be a good sign for the health of the ocean in general – and even efforts to tackle climate change. Whales feed on iron-rich krill, but they also defecate in surface waters – returning nutrients to the ocean that help grow tiny phytoplankton, the foundation of the marine food web. Like plants on land, phytoplankton photosynthesize by using sunlight to convert carbon dioxide into energy and oxygen. They were “ecosystem engineers,” said Herr, who first spotted a large group of whales by accident in 2013 during a research expedition to Antarctic minke whales. He is now planning more expeditions to investigate the enduring mystery of these ocean giants – where they breed. “We don’t know where they go,” Herr said, adding that much more was known about northern hemisphere fin whales. The animals can grow up to about 27 meters (88 feet), although Herr said they now tended to average 22 meters, particularly after whaling targeted the larger creatures. In total, about 700,000 individual fin whales were killed during the 20th century for the oil in their blubber.
