Organ-eating killer whales drive sharks out of their territory

In the 2010 sci-fi thriller repo men, starring Jude Law and Forest Whitaker, has artificial organs fatally taken from people if they don’t make regular payments for their use. It’s a nightmare scenario that thankfully hasn’t manifested itself in the real world.

In the animal kingdom, however, things are a bit different, especially when you are a great white shark in the coastal regions around South Africa. In 2017, two killer whales appeared in the region and immediately began hunting and killing great white sharks. Since then, eight carcasses have been washed ashore, and while this certainly represents a fraction of their kills, all but one have had their livers removed. Some were also missing hearts. Analysis of the wounds left on the sharks’ bodies shows that they were all killed by the same two animals.

While killer whales are known to be capable of this type of attack on other large animals, it is unusual for this to occur so frequently and in such close proximity to shore. That led scientists to wonder how these shifting dynamics might affect shark populations and the rest of the surrounding ocean ecosystem.

Alison Towner of the Department of Ichthyology and Fisheries Science at Rhodes University in Makhanda, South Africa, and colleagues set to work to study the phenomenon. Their results were recently published in African Journal of Marine Sciences.

“Shark-eating killer whales are pretty rare. They’re generally more likely to be found offshore, so it’s quite uncommon to see them off the coast of South Africa chasing large sharks,” Towner told SYFY WIRE.

It’s unclear why the killer whales have moved closer to shore, where they interact more frequently with great white sharks. It is possible that they are responding to a decline in prey species in more distant areas, but the exact triggering event or events are not yet understood. Towner noted that an updated review of the orca is underway and should shed more light on events later this year.

The idea of ​​orca whales attacking sharks and harvesting their organs may seem quite macabre, especially since we often think of nonhuman animals as indiscriminate eaters. However, it actually makes some sense, at least from the orca’s perspective.

“A great white shark’s liver makes up about a third of its body weight and is incredibly rich in lipids. It’s very nutritious,” Towner said.

There is some comfort in knowing that the organ harvesting and subsequent dumping of the bodies isn’t the result of an underwater revenge plot designed to send a message to the other sharks. But even if that’s not the orca’s intention, the sharks got the message and they’re taking them to blue water pastures.

Using trackers and visual observations, scientists have kept tabs on 14 sharks since the orcas arrived in 2017. These sharks have been observed fleeing the area when killer whales appear. And the more often the killer whales show up, the longer the sharks stay away. That might sound like a good thing for South African beach-goers, and a pleasant change of pace for anyone who’s ever seen Jawbut it has the potential to throw a wrench into the region’s entire food chain.

“Killer whales are the wolves of the sea, avoiding them is wise on the part of great white sharks. Time will tell exactly what mechanisms great whites use, but I suspect the sheer trauma of being attacked by more than one killer whale causes them and others to flee in panic. Longer absences may be caused by additional clues such as decaying carcasses or the absence of other sharks in the area,” Towner said.

Great Whites may have a reputation for being the terror of the deep, but they are an important part of maintaining balance in their wider environment. Their absence could have far-reaching consequences for other species, and scientists are trying to get a handle on that. Research is ongoing and Towner indicated that its findings are being used to inform policy decisions in South Africa.

We never thought we’d wish for more great white sharks in the ocean, but for the good of the ecosystem as a whole, it might be best if it were a little less safe to get back in the water.