Whale wars: Why humpbacks save other animals from orca attacks

Whale watchers are sharing images of a rare and 'epic' tussle between a group of orcas and humpback whales off the coast of Jordan River, B.C. Aug. 7, 2016. (Courtesy Pacific Whale Watching Association)

Are humpback whales naturally altruistic creatures? Sort of, according to a surprising new study into an unusual behaviour of one of the ocean's gentle giants.

Humpback whales have been known to fight off orcas – a dolphin species sometimes called the wolf of the sea – when hunting pods target a calf. One of these marine tussles was recently spotted off the coast of Vancouver Island by a whale-watching tour.

But Robert Pitman, a California-based researcher with the U.S. National Marine Fisheries Service, had a hunch that humpbacks might also be defending other species. During a trip to Antarctica in 2009, Pitman watched a humpback whale lift a seal out of the water using its chest – creating a platform for the animal to hide atop from nearby orcas.

When the seal started to slip into the water, the humpback used one of its pectoral fins to nudge the animal back into the middle of its belly.

"It clearly had done this deliberately," Pitman told CTVNews.ca.

"It was at that point that I realized that the humpbacks were there not just to drive off the killer whales, but were there because of the animal that was being attacked."

So Pitman tested his theory. Alongside a team of scientists, he spent five years compiling first-hand observations from other witnesses who saw similar acts of humpbacks intervening in orca hunts.

In total, researchers found 115 cases from across the globe dating back as far as the 1950s. The humpbacks were seen protecting a variety of species, including seals, sea lions and other whales. Those observations were published in a study in the Marine Mammal Science journal in July.

But why?

Pitman calls the humpback behaviour "inadvertent altruism" and said humpbacks may simply be acting out of defence for young whales that are either their calves or close family.

Humpbacks typically live in higher latitudes to feed and move to lower latitudes to breed and give birth. Calves usually live and feed with their mother for one year before moving back to the matriarch's breeding area. Researchers call this behaviour "site fidelity."

Due to this migration pattern, humpbacks tend to be closely related to their neighbours. So when hunting orcas come nearby, humpbacks are more likely to intervene to save another humpback's calf because they are more likely to be related.

But why rescue another species? Pitman says the answer likely has to do with instinct and intelligence.

"If humpbacks were a lot smarter, I think they'd be able to figure out that saving another species is probably not worth the effort. But I don't think humpbacks are all that smart. And they have one very simple instruction, and that is when you hear killer whales attacking, you go and you break it up," he said.

"They end up saving the lives of related calves often enough to make this behaviour worth their while, even if it means sometimes they save the life of a different species."

The altruism debate

Using the word "altruism" to describe the humpback behaviour can be controversial. Any time scientists project a human emotion onto an animal – a phenomenon called anthropomorphism – some people can become alarmed, Pitman said.

"Altruism is a behaviour that humans are intensely interested in and a lot of people think that only humans are capable of this," he said.

But Pitman doesn't go so far as to call the inter-species intervention pure altruism – there's something in it for the humpbacks.

"I think what's very interesting about this humpback behaviour is, like I say, on an individual basis sometimes they do things that aren't in their own best interest, but when you look at it, the overall net effect is it's a survival strategy. It is in their best interest," he said.

"It's kind of a half step on the way to altruism."

Humpback vs. orca: who wins?

There are two main types of orcas: those that eat fish (known in B.C. waters as southern or northern residents) and those that eat mammals and other marine life.

Humpbacks have only been documented intervening in mammal-eating orca attacks, Pitman says, and they typically jump in when they begin to hear the orcas' telltale chirps and clicks.

"Mammal-eating killer whales, when they hunt, are silent because their prey have acute hearing. So they don't make any noises (except for) the occasional contact call, and that's it. But when they start attacking they get quite noisy," he said.

An adult humpback against a pod of orcas is "like wolves around a moose," Pitman said, and one quick swipe of a humpback's tail is enough to "take out" a killer whale, he said.

"The humpbacks aren't very agile, so the killer whales move around them," he said. "These killer whales spend decades living together, so they know their movements quite well."

Still, in all 115 documented cases of humpbacks fighting with orcas, Pitman said there isn't a single recording of an orca being killed.

"Not that anybody has actually seen," Pitman said. "Those killer whales, they stay away from the tails of the humpbacks and the flippers … they have a lot of respect for those adult humpbacks."

Whale fight sightings will go up, Pitman predicts

It's difficult to tell whether cases of humpbacks fighting with orcas are on the rise or if humans are simply paying more attention to whales nowadays, Pitman said.

"I think that's going to happen quite a bit now. The number of sightings is really going to pick up because people are aware it's going on," he said.

He also pointed to the resurgence in humpback whale populations after large-scale whaling ended in the 20th century and greater efforts were made across the globe to protect whales.

This increased interest in whales could lead to more new insights into the mysterious lives of marine mammals, Pitman said.

"As their populations are recovering, I think we're starting to learn things about them that we never knew, and behaviour may be one of those things," he said.