Killer Whales Murder a Baby in a Group Infanticide Effort 

This is evolutionary tragedy at its most grim.

It’s been a rough week for whales. Today, Australians woke up to a shoreline full of 140 dying pilot whales stranded en masse, and just a few days ago, marine biologists published in Scientific Reports the first-ever account of killer whales committing a heinous act: infanticide. What’s even more gruesome is knowing that, in the animal kingdom, it’s not such an uncommon event.

In the paper, researchers from Fisheries and Oceans Canada describe the grim scene that unfolded in December 2016 in Johnstone Strait, a serene, forest-lined channel northeast of Vancouver Island known for its great whale-watching. At first, they’d just heard “discrete and aberrant pulsed calls” on a whale-monitoring system nearby. Sending out a research boat to check out the scene, they found a group of whales that included a newborn so young that its dorsal fin was not yet entirely erect.

A few minutes later, “erratic movements and splashing suggestive of a predation event were observed”. Amid the chaos, they soon realized that the newborn had not surfaced next to its mother for quite some time.

Johnstone Strait: an unlikely scene for a grisly infant murder.


Then, they saw it: one of the males in the group, age 32, with an “object partially white in colour in his mouth.” The neonate’s mother frantically tried to catch her child’s kidnapper, but the kidnapping male’s mother “attempted to manoeuvre between them,” suggesting this infanticide was a team effort. The neonate was last seen alive with its tail between its killer’s teeth.

Minutes later, the killer was photographed, “rostrum to rostrum,” with the dead neonate, whose body was still intact.

The killer, nose-to-nose with its victim.

Towers et al./Scientific Reports

The authors, reviewing their observations in the paper, realized that this was not the first time such an attack had been inflicted on the family of the neonate by the other whales in the group. One female, the neonate’s aunt, appeared to have had been injured before this particular attack. There is no definitive explanation for why this happened, but the authors’ best guess is that the attacking team consisted of an overbearing mother who was dead-set on finding a mate for her large adult son.

The top-left image shows one whale, injured in the conflict; at top right, the mom and her newborn try to escape. On the bottom left, the killer appears. At the bottom right, the angry mom rams into her child's attacker.

Towers et al./Scientific Reports

As appalling as it may be to humans, infanticide is nothing new in the animal world, though this does mark the first time it’s been seen in killer whales. While it has been observed in cetaceans in many situations, one leading hypothesis is that it occurs because it can increase a male’s biological fitness — that is, his ability to pass on his genes.

It’s well known that the mother-son dynamic in killer whales is strong, and previous research has provided support for the theory that post-reproductive female killer whales play a role in finding mates for their sons, as part of an evolutionary strategy to ensure the continuation of the family genes. If this theory applies here, then it follows that the violent whale mother, hell-bent on finding her son a mate, helped organize an attack against the new mother’s child so that she would be forced to mate again — perhaps with the male that just killed her newborn.

This sordid tale may seem better suited for Shakespeare than the sea. However, as researchers consistently demonstrate, humanity’s imagination for tragedy barely registers a PG-13 next to the immoral, unbridled barbarism of nature.

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