Orcas Observed Killing Blue Whales in ‘Biggest Predation Event on the Planet’
Killer whales truly deserve their name. They’ve been observed taking down everything from sea lions to great white sharks. And now, for the first time, they’ve been observed attacking and killing the largest animals on earth: blue whales.
Scientists writing in the journal Marine Mammal Science on January 21 recorded three incidents in which orcas hunted and ate blue whales off of Western Australia’s Bremer Bay.
“This is the biggest predation event on this planet,” study co-author and Oregon State University Marine Mammal Institute marine ecologist Robert Pitman told National Geographic. “The biggest apex predator taking down the biggest prey.”
The first incident occurred the morning of March 21, 2019.
“When first observed, 12–14 killer whales were already attacking a blue whale that we estimated from images to be approximately 18–22 m [approximately 59 to 72 feet] long,” the study authors wrote.
The hunting party consisted of around eight adult females, at least two juvenile females, one adult male and one subadult male. The orcas first attacked and chased the whale until it slowed and began swimming in a circle.
“A few minutes later, three adult female killer whales lined up, side-by-side, perpendicular to the blue whale and rammed headlong into its flank, pushing it through the water and then forcing it under,” the study authors wrote. “At the same time, two other killer whales were attacking the blue whale’s head, and its forward movement stopped. Moments later, at approximately 09:30, while it was still alive, an adult female killer whale put its head inside the blue whale’s mouth and began feeding on its tongue.”
Once the whale died, around 50 orcas joined in to feed on the corpse.
The second incident occurred 16 days later on April 6, 2019. It involved an initial attack group of around 25 orcas and a blue whale calf around 10 to 12 meters (approximately 33 to 39 feet) long. Again, the orcas coordinated their attack by pushing on the whale, preventing it from either diving or surfacing. Again, a female whale attacked its mouth. Once it was dead, a group of around 50 orcas joined in for the spoils.
The last incident occurred March 16, 2021. It was started by 12 orcas, who chased the whale for 97 minutes. The whale was apparently a juvenile and measured 12 to 14 meters (approximately 39 to 46 feet) long. The orcas finished the hunt by lining up perpendicularly to the whale and forcing it sideways, eventually pushing it beneath the water. In the end, 50 to 75 killer whales were present for the attack.
These incidents are notable for several reasons. While orcas have been observed attacking blue whales before, this is the first time they have been seen making successful kills. Further, scientists had previously assumed that successful orca attacks on large whales would need to involve males, which are larger, The Guardian reported. However, all of the observed attacks were led by females.
While the incident is remarkable, researchers think it might be less of a new development than a return to the past. Blue whales are still considered endangered, but their numbers have recovered significantly since they were first protected from whaling in the 1960s, National Geographic explained.
“Maybe what we’re starting to see now is how the ocean used to be before we took out most of the large whales… As some of these populations continue to recover, we have a better chance to see how normal marine ecosystems function,” Pitman told The Guardian.