Why Don't Orca Ever Attack Humans in the Wild?

There are no records of orca ever hunting and killing humans in the wild, despite numerous interactions between the two species.

Orca have been known to prey on whale species larger than themselves and they are the only known predators of great white sharks. Their diet also consists of seals, fish and sea birds.

These apex predators, which can can reach sizes of more than 30 feet in length and weigh up to 11 tons, would make light work of any human in the water, if they were so inclined.

Why don't orca hunt us?

"It's amazing," Deborah Giles, the science and research director for the Washington state-based non-profit Wild Orca, who has been studying one population of killer whales in the Salish Sea—located in the Pacific Northwest—since 2005, told Newsweek.

"There are areas around the world where people are in the water with killer whales not infrequently," she said. "There's certainly been ample opportunity for killer whales to kill humans and they just haven't. It's perplexing. It feels like one of life's mysteries that we're never going to know for sure, because we can't actually talk to them."

The question becomes even more perplexing given the wide range of different animals that orca—which are found in waters all over the world—eat.

While all orca are considered one species (Orcinus orca), Giles said the various killer whale populations should probably be classified into subspecies, at least, if not full species, because they are genetically and culturally distinct. One of the main traits that differentiates these different populations is what they eat. In fact, different orca groups don't see each other's food as potential prey.

"The population that I mostly study in these waters only eat fish," Giles said. "Although they are known to kill porpoise and sometimes play with them to death, we think they don't eat them—they don't take an even a bite out of them. On the flip side, there are other killer whale populations that only eat mammals. And then are the offshore killer whales which are more generalist feeders. We believe that their main prey is sharks and rays.

"It is astonishing, given the wide variety of different food sources that these killer whales around the world become specialists at eating, that there's never been a recorded killing of a human killed by an orca."

Even orca populations in areas of the world where killer whales have been targeted by humans for whaling purposes don't appear to act aggressively towards us, according to Giles.

Orca attacks in the wild

While there have no recorded orca killings of humans in the wild, there have been a small handful of very rare incidents where killer whales have come into contact with humans and posed a threat to people.

Giles pointed to one incident that occurred in Alaska in 2005 when a 12-year-old boy was swimming in a few feet of water in Helm Bay when a killer whale rushed at the boy and bumped into his shoulder, although it did not harm or bite him in any way.

"At the last minute, the whale recognized that it was a human or recognized that it wasn't prey and essentially bent its body in half to flip around and go back out to sea," Giles said.

Another individual who was surfing at Point Sur off the California coast in 1972 reported being bitten by a killer and subsequently required stitches. This is perhaps the only well-documented instance of a wild orca actually biting a human.

But aside from very rare incidents like these, why do killer whales generally avoid attacking humans?. While Giles believes the question is unanswerable to some extent, she said it is likely that cultural factors play a key role.

Like humans, "killer whales have culture, the ability to pass on behavior—almost like trends," Giles said. "They're incredibly intelligent animals. They are masters of their environment, depending on where they're from. Their brains are incredibly complex.

"The physiology of these animals suggests that they are smart enough to know that humans are not prey. Now why is that? I think that it comes down to more of a culture question. They learn to eat what their mothers teach them to eat, and humans have never been part of that diet. Humans have never been part of the menu. I think it might be as simple as that," Giles said.

Giles pointed to the example of the population of fish-eating orca she studies—known as the Southern Resident killer whales—who are known to capture and play with porpoises. This act sometimes results in the death of the porpoise.

However, these whales do not appear to eat the porpoises, despite the fact that some members of the group are starving to death due to a lack of food. This population is endangered with only around 75 members remaining. Among the main threats this group faces is a reduction in the abundance of their preferred prey, Chinook salmon.

"Even in the face of starvation, they don't change what they eat," Giles said. "They're killing the porpoise, it's already dead or dying. And with one bite they can eat the whole thing. Yet these whales just don't see these porpoise as prey. And I think it's the exact same thing with humans—they don't see humans as prey. Thank goodness, they don't see humans as play toys.

"It's like a starving vegan playing with fish along a stream but not eating it. Why the whales don't do it is just such a perplexing, interesting question when they're dying, when their families are dying."

Lori Marino, an expert on the brains of orca, also agreed with Giles that cultural factors are likely the primary reason why there are no recorded orca killings of humans in the wild, although the hugely complex brains of these whales can also provide some important insights.

"The orca brain—especially their neocortex—is huge and very complex and so they clearly can make very fine distinctions across objects," Marino told Newsweek. "This means they would almost never, for instance, mistake a human in the water for prey.

"The kinds of problem solving behaviors they are capable of and have demonstrated make it clear that they are orders of magnitude more intelligent than any animal would be if mistaking one prey item for another. But I think more importantly it has to do with the fact that they have a highly developed limbic system. This is the part of the brain involved in processing emotions. They simply aren't motivated to kill us—in the wild at least."

Marino said the cultural traditions of these whales include learning what to eat and what not to eat, and social etiquette.

"So, while the brain anatomy can tell us something about how cognitive complex these whales are I think the answer lies more so in their cultural practices," she said.

Asked whether one reason the whales don't try and kill humans is that they also recognize us as intelligent, Giles said: "I don't know how to answer that but if there is any animal on the planet, that has the capacity to judge the intelligence of another species besides humans, it would be killer whales."

One final factor that could potentially come into play is the idea that perhaps humans just simply don't look very appealing to orca compared to their normal choice of prey.

"We're not that fatty, which is possibly a part of it," Giles said. "But then if that was the case, you would think that there would be some examples in the past of killer whales eating humans and then just not not doing it anymore."

SeaWorld and orca attacks on humans

While there have never been any recorded orca killings of humans in the wild, several attacks have occurred in captivity in the past 50 years, with at least four of these being fatal. Three of these deaths were caused by the same captive orca Tilikum—the subject of the 2013 documentary Blackfish who was kept at SeaWorld Orlando in Florida for most of his life.

There is some debate among experts regarding whether these attacks in captivity were deliberate or accidental. In Giles's view, Tilikum may have been suffering from mental problems that could have played a role in the deaths, which included 40-year-old SeaWorld trainer, Dawn Brancheau.

"Killer whales are highly social and traditionally quite vocal animals," Giles said. "So, for an animal like this to be in such an unnatural environment most likely caused psychosis. There was aberrant behaviour from Tilikum, for example, for years that was not discussed publicly.

"I personally believe that he was made crazy by the environment that he was forced to live in. It was probably not premeditated. There's no way to know that, of course. But he had interacted with Dawn Brancheau for years and years prior to that. I think that something snapped."