How Orcas Work Together to Whip Up a Meal

Cooperative hunting techniques provide a glimpse into the culture of killer whales.

By Virginia Morell

Photographs by Paul Nicklen

There are no orcas to speak of in Western literature. Although they look like mythic creatures, with their sleek bodies, panda-like colors, and pointy-toothed grins, killer whales don’t figure as characters in our great novels. There’s no orca equivalent of Moby Dick, the great white whale.

Many of us, though, do have an image of orcas, one informed by films of them performing in aquarium shows, such as those at SeaWorld—swimming in endless circles in tiny, sterile pools or leaping for our amusement. Some think captive orcas suffer severe psychological trauma from their sadly shrunken lives.

And that’s heartbreaking, because when you’re out with orcas in the wild, you sense what no show can ever capture: their spirit and sagacity, their joy and cunning, their love of the open ocean and of hunting and of life.

On a cold January day I was surrounded by hundreds of black-and-white killer whales—Orcinus orca, not a whale but rather the largest dolphin—streaking like wolves through the waters of Norway’s Andfjorden, 200 miles north of the Arctic Circle. Their backs and tall dorsal fins glistened in the Arctic twilight as they dived and surfaced and worked in teams to corral, stun, and devour silver herring.

At times an orca would smack the surface with its tail, as if playing patty-cake with the sea. Orcas make similar tail strikes underwater—death knells for herring, said Tiu Similä, a cetacean biologist who helped pioneer the study of orcas in Norway and is an expert on an orca hunting method called carousel feeding. The force of the blows doesn’t always kill the fish, she said, but it does stun many, making them easy pickings. “What we’re seeing here at the surface only gives a hint of what’s happening below,” she said. “Each whale has a role. It’s like a ballet, so they have to move in a very coordinated way and communicate and make decisions about what to do next.”

In spite of the numbers of herring, it isn’t easy for the orcas to catch the fish, which are faster swimmers and form defensive, wall-like schools. Orcas can’t just lunge at them and gulp quantities of fish and seawater as baleen whales do. Instead, like sheepdogs working a flock, they herd the schools into tight groups they can control. “The orcas have to stop the fish from diving,” Similä said, “so they force them to the surface and keep them there in a ball by circling around them.”

Pod members take turns diving beneath the school and looping around it—an orca carousel—while blowing bubbles, calling, and flashing their white bellies to frighten the herring. In response the fish swim even more tightly together. When a carousel is going full tilt, herring leap about on top of the water, desperately trying to escape. “It looks as if the sea is boiling,” Similä said.

Once the pod has the herring under control, one orca slams the edge of the school with its tail—serving up dinner.

But the orcas we were watching weren’t engaged in a classic carousel. They were swimming and diving fore and aft of a mass of fish but not circling beneath them. Even though the sea’s surface wasn’t boiling with fish, the orcas were feasting. Their tail strikes, the stunned and dead bodies of herring, and all the fish scales floating in the water like silver coins told Similä that.

TALES OF THE TEETH
In the waters of North America’s Pacific Northwest, orcas are divided into three ecotypes based on their diet, which affects the wear on their teeth. Resident orcas live in cohesive family groups and eat mostly fish and squid; their teeth have the least wear. Transient orcas, which roam coastlines in small pods, eat mostly marine mammals; their teeth show large chips and cracks from biting into bone. Offshore orcas travel far out to sea and favor sharks, whose rough skin eventually files down their teeth almost to the gum line.

EMILY M. ENG, NGM STAFF; TONY SCHICK. SOURCE: MIKE ETNIER

Carousel feeding is one of several orca hunting tactics that some scientists, Similä included, consider one aspect of the species’ “cultures,” which include strategies for particular kinds of prey. In Argentina, orcas hurl themselves onshore to seize unsuspecting sea lion pups, timing their hunts to coincide with the waves and tides so that they won’t be beached long. In the Antarctic, pod members cooperate to make large waves that wash seals from ice floes. Younger orcas learn these techniques from older ones.

Orcas haven’t been documented, however, cooperatively hunting with whales. Indeed orcas prey on sperm, gray, fin, humpback, and many other whales, which is why whalers called them killers of whales. It’s also why Similä was perplexed. Normally the orca pods here fished alone, but on this day humpbacks and fins were swimming among the orcas and eating the herring too. Around us dorsal fins of various shapes and hues broke the water. Orcas shot past, rounding up herring, while humpbacks hurtled skyward, jaws agape, gulping fish before the orcas could pick them off, and the fin whales merely showed their curved fins as they caught a quick breath before sinking back into the depths to feast.

“I’ve never seen anything like this,” she said. “Are they all working together to catch the fish?”

Because humpbacks use a method similar to carousel feeding—circling a school of fish or krill, then blowing bubbles to herd them into a ball—Similä thought they might be cooperating with the orcas. Or the orcas and the whales might be “travel feeding,” simply herding the immense school into a tighter group, then slapping the edge of the herring ball for a quick meal before moving on. “But travel feeding takes more energy than the carousel,” Similä said. “And with so many herring here, a carousel would seem to make more sense.”

But the orcas never lingered long enough to carousel feed. They, the humpbacks, and the fins continued to rush past us as if speeding to a gala event, stopping now and then to snack. When we turned back toward our home base, a handsome yacht called the Ylajali, the moon was up, and the milky seas still rippled with whales on the move.

Orcas, members of the Delphinidae family, the marine dolphins, are the most widely distributed of all cetacean species. Yet despite being found in every ocean, often close to shore and at every latitude, from the Arctic to the Antarctic, they remain a mystery. We don’t even know how many full-fledged species and subspecies are represented in the rough estimate of their overall population, which is thought to be at least 50,000.

Is that a healthy number? Or are they endangered? No one knows, because researchers began counting them only in the 1970s and aren’t sure how many are found in each of the ecotypes now recognized. Here in the North Atlantic there may be multiple ecotypes; Similä and I were observing orcas that specialize in feeding on herring. These orcas range across the Norwegian and Barents Seas and were estimated at around 3,000 in 1990. About a thousand of them—Similä and her colleagues call them Norwegian orcas—follow herring into the fjords. But herring aren’t predictable prey. Their numbers can vary dramatically from year to year, and they don’t live in the fjords year-round. They spawn along the coast in the spring, disperse into the Norwegian Sea in the summer to feed, and migrate in massive schools in the late autumn to an overwintering area, either off Norway’s coast or in its fjords. Wherever they go, the orcas follow.

Overfishing by humans in the early 1960s disrupted this pattern, and for a time orcas vanished from Norway’s fjords. In the early 1980s herring populations rebounded, and orcas were again spotted in fjords south of Andfjorden. Similä, who’s originally from Finland, was then a graduate student, researching plankton in Finnish lakes. She heard that biologists were starting orca safaris in Norway and volunteered to work on their boats. On her first day a male orca’s tall dorsal fin pierced the water beside the rubber dinghy she was riding in. The sight left her speechless—and erased all thoughts of plankton. She switched to orcas the next day.

For the next 20 years she followed the orcas every winter as they headed into the fjords in pursuit of herring. She and her colleagues photographed as many orcas as they could so that they could identify individuals, and they snorkeled with and filmed them as they fed.

“In those days nothing was really known about these orcas,” Similä said. “People were told that they were pests and dangerous—that they were eating all our fish.”

Fishermen shot orcas on sight, killing 346 between 1978 and 1981, when the official culls stopped. Many Norwegians continued to consider orcas rapacious herring-eaters until 1992. That year a television station aired footage from Similä’s study showing them daintily eating one fish at a time rather than gluttonously gulping down entire schools.

Orca pods that lost members to a shooter or had a wounded member appear to have never forgotten. “You can see scars on some orcas from the bullets,” Similä said. “We could never get close to those pods. You still can’t. As soon as they hear a motor, they move away.”

Orca pods are led by the founding matriarch, and Similä thinks these “wise mothers” teach their calves to avoid fishing boats, thus preserving the pod’s memory. “I don’t know how they communicate this. Maybe they just lead the others away when they hear a boat’s motor. But they have some way of telling them, Look out—that’s bad, that’s dangerous.”

One day, after seeing orcas spouting on the far side of the fjord, we motored across the two-mile expanse of sea into a calm lagoon. “It’s a whale Eden,” our guide proclaimed as orca pods surged nearby, their dorsal fins riding like sails above the sea, and humpbacks lunged for fish. One pod’s calves playfully surfed in the wake of our boat and then, when the motor was idling, popped up nearby, like prairie dogs, to spy on us. Although these orcas weren’t streaming through the sea, as they’d done on our first day, they still weren’t carousel feeding.

Similä admired the way each orca had a role in the hunt. She’d seen how adults guided younger ones, how calves imitated their mothers’ tail slapping, how pods sometimes made long journeys to the herring’s spawning grounds, apparently to keep track of the fish. By attaching satellite tags to several of the orcas, she and her colleagues had mapped some scouting missions. “One of the orcas traveled so far and so fast—hundreds of kilometers in one day—we thought he was being pulled away by a ship,” she said. “Now I just laugh at myself for thinking such a thing.”

Similä tells an orca story that shows how little we know about them. In 1996 the team spotted a calf with a spine and dorsal fin that had been severely injured, probably from a boat strike.

“We named him Stumpy because of his damaged dorsal fin,” Similä said, adding that she doesn’t actually know whether the calf is a male or a female. “He’s not like other killer whales. He can’t hunt, and they care for him.”

Instead of living with a single pod, Stumpy swims with at least five different ones, all of which feed him. Once, Similä watched as two females came dashing through the waves, each carrying a large herring for Stumpy. She thinks the orcas understand that a boat injured him, because they keep him away from boats.

“Stumpy is the biggest mystery to me. I don’t know what will happen when he becomes sexually mature,” Similä said. “But the other orcas know he needs help, and they help him.”

Some researchers have suggested that an orca pod has such tight social bonds that its members respond to other animals and their environment as a single-minded group. That may be why entire pods strand when only one sick member heads for shore. And why some males die after the death of their mother. Perhaps it’s also why so many orcas help Stumpy.

When you’ve spent much of your life around beings that live in cooperative societies, remember their past, and care for their weakest, you learn to be open to what else they might be capable of. So Similä entertained the idea that the orcas had joined with the humpbacks and fins to hunt the fish.

She later changed her mind. “No, they’re not working together,” she told me in a phone conversation after I’d returned home. “Those humpbacks are just spoiling everything the orcas do. Every time the orcas get the herring organized, the humpbacks wreck it. The fin whales are taking advantage too.”

The orcas didn’t seem to mind. They never made any effort to escape the freeloaders or fight them or chase them away. Maybe this equanimity was evidence simply of the abundance of herring in Andfjorden that winter—more than enough for all.

No stranger to brutal temperatures, Paul Nicklen grew up in the Canadian Arctic. This assignment had him diving in frigid waters up to 50 times a day—a job that might have been easier had he not had pneumonia.

Fonte:  http://ngm.nationalgeographic.com/2015/07/orca-feeding/morell-text