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Scientists witness orcas kill the world's largest animal: the blue whale

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It was once thought that nothing could take down the world's largest animal, the blue whale. But scientists have witnessed something unusual that shows these giants do have a predator to worry about.

LEILA FADEL, HOST:

It was once thought that nothing could take down the world's largest animal, the blue whale - aside from humans, of course. But scientists have witnessed something unusual that shows these giants do have a predator to worry about. NPR's Lauren Sommer has more.

LAUREN SOMMER, BYLINE: It was a stormy morning, and whale researcher John Totterdell was on a boat off the coast of Western Australia with some students. They spotted some dark shapes in the water, a group of killer whales.

JOHN TOTTERDELL: Then we saw a lighter, gray-blue animal, much larger.

SOMMER: Then they saw blood in the water.

TOTTERDELL: Within seconds, I realized, oh, my God, they're - a pack of killer whales are attacking a blue whale.

SOMMER: Totterdell, who is lead researcher for the Cetacean Research Centre in Australia, almost couldn't believe it. The 60-to-70-foot whale was still alive and was fighting back against killer whales that were making coordinated attacks.

TOTTERDELL: It was a good 10, 12 that were active in keeping this animal harassed, wearing it down, just tiring it out.

SOMMER: The blue whale got weaker. Then two killer whales leapt on top of it, forcing the blue whale under the water until it eventually drowned. The scientists saw the first thing the killer whales ate was the tongue.

TOTTERDELL: I couldn't tell you why, but it's - yeah, preferred cut.

SOMMER: Totterdell says while killer whales were known to attack blue whales, no one had documented them being successful before. And there are two other recent examples which Totterdell and colleagues published in the journal Marine Mammal Science. He says because they took down the largest animal on the planet, it shows that killer whales are the top predator in the ocean.

TOTTERDELL: It just enforced what I already knew - that they were highly intelligent. And to take on and successfully take down an adult blue whale has lifted the bar way higher than I would ever imagine.

SOMMER: So how does a blue whale researcher feel about it?

JOHN CALAMBOKIDIS: As a scientist, I tend to look at these things, you know, maybe sometimes a little less emotionally. But I'm affected by it emotionally.

SOMMER: John Calambokidis is a blue whale biologist at Cascadia Research. He says even if it's hard to watch, it's just part of nature. And the reason these attacks may seem rare is because blue whales used to be rare. They were decimated by commercial whaling.

CALAMBOKIDIS: As whales and large whales recover, we might see that these attacks become more common.

SOMMER: Killer whales may be re-learning this now that blue whales are coming back, and they pass that knowledge on to the next generation in their family groups, one of the reasons they're at the very top of the food chain.

Lauren Sommer, NPR News.

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