For the first time ever, researchers have witnessed an orca committing infanticide. The discovery could have impacts on how we interpret the whales' social structures and behavior.
Despite being feared by pretty much everything else in the ocean – from porpoises to great white sharks – orca are surprisingly harmonious when it comes to each other. This makes the incident that occurred as a team of scientists were watching the whales in the waters off British Columbia, and described in Scientific Reports, all the more extraordinary.
“We knew right away that this was a remarkable event,” Jared Towers, a cetacean researcher with Fisheries and Oceans Canada, told The Guardian.
“We’ve been looking at killer whales for years on this coast and around the world – I study populations in different parts of the world – and witnessing aggressive behaviour between killer whales is almost unheard of.”
They were in the area because they had heard reports of the orca making strange vocalizations. When they arrived, they found a group of the whales, including what looked like an infant no more than a few hours old. With nothing much else to report, they were about to leave when they spotted a load of splashing and went over to investigate.
The first thing that alerted them to the fact that something wasn’t quite right was that they had lost sight of the baby. Then a male orca swam right under the boat clutching the infant in his mouth.
It turned out that this male belonged to a different group. He had separated the newborn from its mother, who was desperately trying to get it back but was herself being hindered by the male's own mother who was also in the midst of the fray. Eventually, the baby’s mother managed to deliver a substantial blow to the side of the male, the water frothed with blood, and the event was over.
The occurrence has been described by the researchers as “infanticidal teamwork”, as the male’s mother was actively helping him carry out the attack. What's more, this is the first time that infanticide has been recorded in the cetaceans. Why they did it is still not fully understood, but the fact that neither attacker ate the remains suggests it might all be about sex.
The researchers suspect that the male and his mother, who were from another group, wanted to kill the newborn in order to cause its mother to become fertile once again. This would allow him to then mate with her, and father his own offspring. The fact that the mother helped the male out also makes sense as female killer whales closely associate with their sons, so she may have wanted to help create extra mating opportunities for him.