In January 2022 off Adelaide Island, Antarctica, the snow was falling so thick and quietly, it felt like traveling through hyperspace.
“Silence is noisy, so that was super spooky,” says Bertie Gregory, a National Geographic Explorer and host of Animals Up Close on Disney+.
Gregory had traveled across the Drake Passage that separates South America from the southernmost continent to film a rare orca population called B1. Known for their unique strategy of creating waves that knock seals off pieces of ice, these genetically distinct Antarctic orcas, likely number only around a hundred.
So when Gregory and his crew of filmmakers and scientists began following a small pod of B1s hunting seals in the driving snow, they thought they’d hit the jackpot. But what those onboard couldn’t know at the time was that the orcas weren’t alone.
First, the pod zeroed in on their prey—a Weddell seal lying smack-dab in the middle of a large piece of ice. (Learn how orcas can kill the largest animal on Earth.)
“They swam under the chunk of ice, just like they normally do, but we could see no breaking wave, and we were like, ‘Oh, they must have messed it up,” says Gregory. “But instead they were making an underwater shockwave.”
With an aerial drone, the crew watched as the orcas disintegrated the seal’s icy platform from below. It worked, forcing the seal into the water, where the pod then spent several minutes tiring the animal out.
“Then, all of a sudden, two humpback whales just turn up,” says Gregory. “They do this amazing trumpeting noise [that’s] so loud, it reverberates in the hull of the boat, like an elephant trumpeting.”
Scientists have witnessed and filmed humpbacks, which feed on tiny crustaceans called krill, disrupting orca hunts many times, but only a few times among B1 orcas. Because the predators sometimes target humpback calves, the whales may antagonize orcas when they see them hunting, experts say. (Read more: “Why humpback whales protect other animals from killer whales.”)
In this instance, the humpbacks were too late to intervene on the seal’s behalf, but between their unmistakable trumpeting and decision to swim right into the orca pod, Gregory believes the pair were trying to mess up the orca’s hunt and even protect the seal.
Leigh Hickmott, a whale biologist at the University of St. Andrews in Scotland and Gregory’s collaborator on a project to study B1s, agrees.
“I think it shows very clear signs of altruism,” Hickmott says.
Exploring humpback motivations
Humpbacks possess big pectoral fins and tails for swiping and smacking other animals in defense of themselves or their calves. Their pectoral fins also boast knobs at the ends, each of which can become encrusted in barnacles and act like a pair of sharpened brass knuckles in a fin fight.
Scientists have documented many occasions all over the world of humpbacks ramming, slapping, and raking orcas. Such injuries raise the risk of infection and injury, so orcas are understandably wary of humpbacks. (Read about orcas that kill great white sharks.)
However, the Antarctic humpbacks didn’t engage physically. They just swam over and trumpeted. Why?
It might be an example of mobbing behavior, says Hickmott. “It’s better to know where a predator is, and let it know that you know where it is, so it can’t surprise you or your kin,” he says. “Often a surprise attack is a predator’s means for success.”
Still, swimming headlong into an orca pod is dangerous. And to do so when the B1s aren’t even attacking another humpback, but a seal, seems to suggest the humpback whales are, as Hickmott believes, attempting to save the prey—or at least prevent the orcas from getting an easy meal.
An emotional investment?
As lead research biologist for the California Killer Whale Project, Alisa Schulman-Janiger has seen humpbacks bellow at, throw water on, and physically assault orcas trying to feed on a fresh kill.
She remembers one 2012 incident in which humpbacks swam from miles away to spend seven hours harassing killer whales preying upon a gray whale calf.
“They had something to say about what was going on. They were not happy,” she recalls. What’s more, there was krill everywhere, which the whales ignored almost entirely.
“You’re not going to forgo food for seven hours to scream at killer whales, when you have one of your own calves around,” adds Schulman-Janiger, who was not involved in the Antarctic expedition. “You don’t waste that much energy unless you’re really emotionally invested.”
The Antarctic story has another twist.
After finally killing the seal, the orca matriarch grabbed the dead animal in her mouth and swam toward the humpback whales, “like, ‘See? See?’” Gregory recalls.
“It was almost like she was showboating,” he says.
Such behavior is difficult to interpret, cautions Schulman-Janiger. But she’s also seen a male orca drag a freshly killed gray whale to the bow of a research vessel. (Learn more about the secret culture of orcas.)
“I couldn’t believe he pulled the carcass there, as if he was showing off,” she says.
Climate change advantage—for prey
Regardless of their true motives, there’s no question there’s much more to learn about orca and humpback behavior. Yet for B1s, that may become more difficult as their population falls.
“Our data over a 10-year dataset shows that they’re declining at about 5 percent per year,” says Hickmott.
“As the planet warms, and the glaciers retreat, we’re seeing more beaches and more islands exposed,” he says. The Antarctic Peninsula has warmed almost 5.4 degrees Fahrenheit since 1950, according to the National Center for Antarctic Research.
This gives the Antarctic orcas’ favorite food an advantage.
“It’s easier to haul out on beaches and on shorelines than it is on the pack ice,” Hickmott explains.
“And so they end up out of reach of our killer whales and these hunting techniques that they’ve evolved to use.”
Still, it’s possible orcas will shift to new hunting strategies—and those meddling humpbacks may follow.
The National Geographic Society, committed to illuminating and protecting the wonder of our world, funded Explorer Bertie Gregory’s work. Learn more about the Society’s support of Explorers highlighting and protecting critical species.