A female orca swimming with her newborn calf before the vicious attack. Image: Jared R. Towers, et al via Scientific Reports

Researchers believe it was a crime of passion. But whatever the motivation, this is hard to stomach.

Marine biologists at OrcaLab off the coast of Vancouver witnessed a horrifying scene: a mother-son pair teaming up to target and kill a newborn calf in the first documented case of infanticide among killer whales.

Responding to strange calls they overheard on an underwater microphone, the researchers arrived at the scene to find a mother orca swimming with several of her young, including a newborn they estimated was only about a day old. Behind the group was a 32-year-old male and his 46-year-old mother.

After a struggle that they said looked like “a predation event,” the male surfaced with the baby orca hanging from his mouth. The newborn’s mother was desperate to rescue her baby, and she repeatedly rammed the male, once so hard the scientists saw a spray of blood.

The infant’s mother repeatedly rammed the attacker in an attempt to rescue her baby. Image: Jared R. Towers, et al via Scientific Reports

Then the attacker’s mother got involved. She blocked the panicking baby’s mother, and then helped her son push and drag the baby around for four hours. The baby couldn’t surface for air, and it eventually drowned.

While plenty of species practice cannibalism, this didn’t seem to be motivated by hunger, as the attacker and his mother didn’t feed on the baby. Rather, in a study published in the journal Scientific Reports, the researchers hypothesize the attacker wanted to mate with the baby’s mother.

Robert Pittman, NOAA/Wikimedia Commons

As long as she’s nursing a baby, a female orca won’t mate. But if her child dies, she’ll stop lactating and be ready to mate again. And the accomplice? They believe she had a vested interest in seeing her son succeed in order to extend her bloodline.

Other species like lions, zebras and dolphins have been known to kill the young of potential mates, but this is the first time this behavior has been seen in whales.

For what it’s worth, we hope that mother orca never gives her baby’s attacker the time of day.