On March 21, 2019, researchers in Western Australia were studying orcas, a species also known as killer whales. Suddenly, the scientists witnessed a phenomenon that no one had previously seen. They observed orcas killing the world’s largest animal, a blue whale.
On that day, this group of researchers from the Cetacean Research Center was traveling on a boat to their usual orca observation site. However, when they stopped to remove some trash from the water, they suddenly noticed some splashing in the distance. They observed the dorsal fins of several killer whales and saw that they were attacking a large whale species. That whale turned out to be a blue whale.
In this attack, 12 orcas were collaborating to take down a blue whale that was between 59-72 feet long. The whale’s entire body was covered in teeth marks. Its fins were bitten off, and its face was torn apart, showing exposed bone. Some of the orcas were slamming into the whale’s sides, while others were already feasting on different body parts.
This type of hostile behavior is an old habit for orcas; they use these methods reliably when hunting other whale species. First, they bite the fins, tail, and jaw of the whale to slow down their prey. Then, they push its head underwater in order to suffocate it. Some orcas also swim below to prevent the whale from diving.
Orcas usually hunt in packs, which usually consist of their families. Often, the females lead the hunt. The orca calves tend to watch from the side, but they also join in on occasion. In the end, orcas share their meal even with extended family. On the day of the attack in question, the researchers saw 50 orcas consuming one blue whale.
In the journal Marine Mammal Science, a recent article described orca attacks on two other blue whales by the same pack of orcas. In 2019 and 2021, two younger blue whales, one calf and one juvenile were killed by the orcas. These incidents happened in Bremer Bay, Western Australia, a typical migration route for blue whales and an area where large groups of orcas often hunt.
Since these two species have coexisted in the oceans for thousands of years, researchers theorize that orcas have used that time to perfect their hunting methods for these large aquatic mammals.
While it is uncertain whether or not blue whales were a major part of orcas’ diet historically, they at least seemed to have contributed to the food source of killer whales considerably.
[Sources: Science News for Students ; npr.org ]