Science

Polar bear hunting a reindeer caught on tape for first time

In August 2020, biologist Izabela Kulaszewicz was settling in for a lazy evening at the Polish Polar Station, Hornsund, on Norway’s Svalbard archipelago, when a message came over the radio. Two researchers had just spotted a polar bear. Having wanted to see one all summer, Kulaszewicz, of the University of Gdańsk, and a handful of other scientists rushed outside.

About 100 meters away, a chubby female polar bear was sniffing the air and walking toward the coast. Soon, she disappeared into a dip in the tundra, only to emerge seconds later, galloping toward several reindeer on the shoreline. She went after one bull and chased it into the sea (see video, above). Less than 25 meters offshore, the predator sunk her claws in the reindeer’s back, bit its neck, and forced it underwater. The reindeer was dead within 1 minute.

The cook at the research station caught everything on film, making it the first video evidence of polar bears hunting and eating reindeer—something that had long been assumed, but never clearly seen.

“I was shocked,” Kulaszewicz says. “I thought reindeer were good swimmers, and the bear would have a bigger problem catching the reindeer. But it was totally different.” After dragging the carcass ashore, the bear ate more than half of it in one sitting.

Polar bears haven’t always hunted reindeer. Their favorite dish is seal—which they catch through holes in the ice far offshore. The blubber from one adult ringed seal can help a polar bear survive for more than 10 days. If they eat enough blubber, they can fast for months.

But as climate change melts sea ice earlier in the year, more polar bears are forced to spend their summers foraging on land. Polar bears have been seen eating bird eggs, rodents, and even trash at landfills. “If it moves, or even doesn’t move, there’s a good chance they’ll try to eat it,” says polar bear biologist Andrew Derocher of the University of Alberta, Edmonton, who wasn’t involved in the new study.

Kulaszewicz and her colleagues describe the remarkable hunt in a paper published earlier this month in Polar Biology. The paper includes at least 12 other reports of bears pursuing or eating reindeer, suggesting these events are becoming more frequent, they write. But whereas previous reports don’t always note whether the reindeer were killed or scavenged, the new report shows polar bears can successfully hunt reindeer, Derocher says. “We don’t see these sorts of events very often. We quite often see the aftereffects.”

The study’s senior author, Gdańsk ecologist Lech Stempniewicz, says he finds it extraordinary that the hunt took place in the sea. Reindeer can swim and run well over long distances, but “in a triathlon consisting of sprinting; swimming in shallow waters with uneven, rocky bottoms, skerries, and ice floes; and wrestling, the bear is second to none,” Stempniewicz, who has worked in the Arctic for more than 50 years, wrote in an email.

Individual bears like this one can learn unique behaviors, Derocher says, and they latch onto whatever works. “I would bet that that bear comes back year after year to the Polish station at Hornsund and will keep trying to do the same thing,” Derocher says. Sure enough, researchers saw the same bear at the water’s edge with another reindeer carcass 1 day after the first hunt. Seemingly still stuffed, it left most of the second kill for the foxes and gulls.

Having evolved without predators, the approximately 20,000 reindeer that live on Svalbard are enticing prey. Polar bears could supplement their diets with reindeer in the summer when sea ice is low, Stempniewicz says.

“We could view this as a little piece of good news, at least for the local polar bears,” says Steven Amstrup, chief scientist at Polar Bears International. But he stresses that new hunting behaviors on land will not make up for the loss of the sea ice habitat where polar bears evolved. “It’s a really interesting observation, and it may have some near-term value for some number of bears,” Amstrup says, “but in the long run, I can’t imagine that it’s really going to be the salvation of polar bears.”

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