National Geographic captured humpback whales interrupting orcas that were hunting a seal in Antarctica.
Humpbacks have been documenting disrupting orca hunts in the past, but it's not clear why.
One expert said the seal may also have been trying to hide from the orcas behind the huumpbacks.
Remarkable footage, taken in Antarctica last year, showed a pod of killer whales that were hunting a seal getting briefly disrupted by a pair of humpback whales, prompting some to suggest the giant creatures were swooping in to save the seal.
The encounter, which was captured in January 2022, was featured in the National Geographic series "Animals Up Close." Host Bertie Gregory was observing B1 orcas, a distinct population numbering around 100, which hunt by creating waves to knock seals off of ice.
After the pod of orcas targeted a Weddell seal, successfully destroying the ice it was on and forcing it into the water, they tried to tire the seal out. But then, Gregory said in the video, two humpback whales appeared out of nowhere.
"That can't be a coincidence that the humpbacks turned up now. They must be going over to try and disrupt the hunt," he said, adding they were "right in the middle of it."
Unfortunately for the seal, the small orca pod prevailed, with one of them ultimately carrying away the seal in its mouth, and curiously in the direction of the humpbacks.
Leigh Hickmott, a whale biologist at the University of St. Andrews in Scotland who works with Gregory on studying B1s, told National Geographic he believes the humpback's behavior was a clear sign of "altruism."
But while humpbacks have been documented on numerous occasions disrupting orca hunts, it doesn't necessarily mean their intentions were to save the seal.
"All of us would like to think whales show empathy," Andrew Trites, director of the Marine Mammal Research Unit at the University of British Columbia in Canada, told Insider, "but in the end, I think it's all about their own self-preservation."
While killer whales do not pose a direct threat to adult humpback whales, which are much larger than orcas, killer whales do prey on humpback whale calves. Humpbacks will become agitated when killer whales are around, especially when the orcas are engaged in aggressive behavior like hunting, even if their target is another species, Trites said.
Biologists believe that the humpbacks may engage in anti-predator mobbing behavior, where they confront the killer whales to get them to leave the area, which is in the best interest of the humpbacks collectively even if a calf is not immediately under threat.
Trites compared it to the way an eagle can be flying and suddenly get dive-bombed by a group of crows out of nowhere. Even though the eagle is not a direct threat to the crows, it is a threat to their chicks and eggs, so it's in their best interest to force the eagle away.
In the case of orcas and humpbacks, it may also be the seal that's forcing the close encounter. While most people believe the humpbacks are swimming over to save the seal, the seal may actually be swimming toward the humpbacks to save itself.
Trites explained that in British Columbia there are many occasions where sea lions come under attack by killer whales and find something really big to take refuge behind — including bigger whales.
"Most people interpret it as, 'Oh, the whales came to save the sea lions.' I hear that over and over," he said. "But what I see is a relatively small, defenseless creature trying to get away, so that can be getting in and around humpback whales, or can be getting in or around someone's boat, which often happens too."
Sea lions and seals have been captured hopping onto boats in order to evade killer whales. Footage captured last year off the UK's Shetland Islands showed a clever seal appearing to use a mussel farm to hide from a pod of killer whales.
Robert Pitman, a marine ecologist with the US National Oceanic and Atmospheric Administration, described a similar encounter that he witnessed in Antarctica in 2009 to Hakai Magazine, which also involved orcas, humpbacks, and a seal. Pitman said that after the orcas washed the seal into the water, it quickly swam towards a pair of humpbacks that had shown up.
The encounter got even more remarkable, as the humpback rolled over onto its back and the seal ended up propped up safely on its stomach and out of the water.
Whether or not the humpbacks in the more recent encounter were engaging in mobbing, or the seal itself sought out the humpbacks as a large object to hide behind, Trites said, "It's always interesting when we see these species coexisting and interacting and how they get on together."
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