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Off the coast of South Africa, a small group of orcas with an apparent taste for shark liver have been taking out great white sharks since at least 2017. And, honestly, that’s not even the strangest thing killer whales have been up to lately.

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Great white sharks are typically considered apex predators. They sit at the top of the ocean’s food web with no natural predators of their own, most of the time. But yeah, we need to talk about one pretty bizarre exception to this rule.

Because, off the coast of South Africa, something has been taking out great white sharks since at least 2017. And that something is a small group of orcas with an apparent taste for great white shark liver. And, honestly, that’s not even the strangest thing killer whales have been up to lately. [♪♪ INTRO ♪♪] Killer whales, aka orcas, are the biggest members of the dolphin family, with females averaging 7 meters long and males averaging 8 meters long.

The longest recorded male reached 9.75 meters in length. They live basically everywhere, in all the oceans of the world, from north pole to south pole, in open ocean and in coastal waters. And all the orcas in the world are currently considered to be part of a single species.

But there might actually be more than one species or even several subspecies of orcas. We’ve talked before about how defining species can be complicated and that is definitely the case for killer whales. Populations living in different places look a little different from each other, specialize on different kinds of prey, and exhibit different behavior.

So, for now, these different populations often get referred to as ‘ecotypes.’ And while ecotypes seem to share physical features in common, like the size and shape of their dorsal fins and white patches, their DNA doesn’t always group them together as being more closely related to each other than to other ecotypes. So as an example, some researchers have split the orcas that live around Antarctica into four-ish ecotypes, labeled A through D. I say “four-ish” because type B is kinda split into two subtypes based on size.

And one study of their mitochondrial DNA, the genetic material that’s only passed on by mothers, found that some Type A orcas were more closely related to Type B and C orcas, but others were closer to orcas that live outside of Antarctica! So it’s not clear how many ecotypes there really are or what’s going on with populations that don’t seem to match an ecotype. Among the more well-studied populations are the three ecotypes found in the Pacific Northwest, called resident, transient or Bigg’s, and offshore.

And there are even a couple different communities within the resident ecotype, in case the ecotype thing wasn't confusing enough on its own! The different Pacific Northwest ecotypes also have different diets, specializing almost exclusively on salmon, marine mammals, and sharks, respectively. And we know less about the offshore ecotype than the others presumably cause they're way off shore.

They're just further away. And one thing that is clear is that cultural transmission plays a big part in shaping the unique preferences of each ecotype. And sometimes that can lead to, interesting behavioral fads.

Take, for example, the so-called “dead-salmon carrying” trend of 1987. That summer, one female from a southern resident pod in Puget Sound started carrying around a dead salmon for reasons unknowable to us. Over the next five to six weeks, orcas from two other pods in the area started doing it, too.

And then, it stopped. Until the next summer, when the trend made a brief comeback, never to be seen again. More recently, off the coast of South Africa, a small group of orcas seem to be on a bit of a fad diet, going after the liver, and sometimes other organs, of great white sharks.

This behavior was first reported in 2017, with two orcas researchers named Port and Starboard seeming to be the trendsetters, though Starboard has since been spotted hunting with at least four others. By June of 2022, eight great white sharks with clear signs of orca predation had washed ashore with seven of them missing their livers, and another predation event was filmed in June of 2023. One previously published account of an attack described an orca trying to roll a shark onto its back, a position that often results in what’s called tonic immobility in sharks.

It’s a trance-like state in which the shark stops struggling, making it easier for the orca to bite the shark’s abdomen behind its pectoral fin to get access to its liver. And while orcas aren’t exactly counting calories, the livers of great white sharks are pretty fatty and energy-rich, which might explain why they prefer them to the rest of the shark’s body. Now It’s not clear yet how this specialized hunting behavior got started or how it’s transmitted.

It’s thought that older female matriarchs teach younger whales in their extended families their social and ecological knowledge, but Port and Starboard are males. There are reports of juvenile male orcas doing things that, like if human teenagers did them we’d call it messing around, things like poking at crab traps. But the shark-hunting by Port and Starboard has gone beyond that, with other orcas picking up their tactics, either through pure imitation or some kind of social learning.

And while this has been going on in South Africa, orcas around the Mediterranean have been getting up to shenanigans of their own. If you’ve been on the internet this summer, you’ve probably encountered the story of orcas around the Strait of Gibraltar declaring war on boat rudders. Since May of 2020, a number of boats off the coasts of France, Spain, and Portugal have been incapacitated, and three were even sunk, by orcas.

Some researchers have speculated that one adult female started doing this because she had a traumatic encounter with a boat, and other orcas have started to imitate it. But it might just be that the orcas are having fun wrecking stuff and it’s spreading culturally as a novel behavior. Like planking, for the elder millennials out there.

We don’t actually know why they’re doing it, so while it’s fun to call it a war on yachts, we can’t even say for sure if it’s aggression. So what does it mean if orcas from different places have different behaviors that are passed on to other orcas? Well, in the case of longstanding, relatively stable things within ecotypes, like what to eat and where to go, that are passed on vertically from mother to calf, researchers definitely call it culture.

But it’s harder to classify the short-term trends that are transmitted horizontally, say from male to male within groups. And I can’t decide whether the fact that orcas have both makes them more or less of a Bizarre Beast. The Bizarre Beasts pin club subscription window is open from now until the end of September 18th!

Joining the club gets you this beautiful orca pin and helps us keep making the show. We liked the orca design so much that we made shirts! You can get this month’s pin art on a t-shirt for a limited time, it’s only available this month, September of 2023.

This episode was sponsored by Planet

Wild: a community that helps our planet and ecosystems bounce back from ocean pollution, deforestation, and species extinction. Every month, the Planet Wild community goes on an environmental protection mission. These missions are based on community votes and vetted for effectiveness, and lasting impacts, and then documented in videos on their YouTube channel for 100% transparency. Their videos are educational, with a focus on real world action.

And their missions are all driven by a community that anyone can join. This summer they partnered with a grassroots anti wildfire organization in Sicily to train civilians to safely protect their forests. You can watch that video here.

Or you can check out this video about their work restoring a river ecosystem after an ecological disaster. Thanks for watching and thank you for supporting Bizarre Beasts! [♪♪ OUTRO ♪♪]