Walruses, which weigh up to 1,300 kilograms with huge fangs and almost impenetrable skulls, are almost impossible to kill a hungry polar bear. But new research suggests that some polar bears have invented a solution: hitting walruses on the head with a block of stone or ice.
For more than 200 years, Inuit in Greenland and the eastern Canadian Arctic have told stories of polar bears (Ursus maritimus) that use such tools to help kill walruses. However, explorers, naturalists, and writers have often dismissed such stories, relegating them to myth along with tales of bear-changing shapes.
The persistence of these reports, including a report by an Inuk hunter in the late 1990s, along with photos of a male polar bear named GoGo at a Japanese zoo using tools to obtain suspended meat forced Ian Stirling and colleagues to investigate further.
“It was my general observation that if an experienced Inuit hunter tells you they saw something, it’s worth hearing and it’s very likely to be correct,” says Stirling, one of the world’s leading biologists on the polar bear.
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Researchers reviewed second-hand historical observations of the use of tools on polar bears reported by Inuit hunters to explorers and naturalists, as well as recent observations by Inuit hunters and non-Inuit researchers and documented observations by GoGo and the Browns, the closest relatives of the polar bears, using captive tools to access food. This review suggests that the use of tools in wild polar bears, although uncommon, occurs in the case of walrus hunting due to its large size, researchers in the Arctic reported in June.
“Really, the only species you’d have to hit in the head with a piece of ice would be a walrus,” says Andrew Derocher, director of the Polar Bear Science Laboratory at the University of Alberta in Edmonton, Canada, who was not involved in the new study. . I suspect it may be some polar bears that do this behavior. For example, if a mother bear figured out how to use ice or stone this way, “it’s something that would take its offspring,” but it wouldn’t necessarily acquire a skill that polar bears across the Arctic would acquire, he says.
Among animals, the use of problem-solving tools was considered a marker of a higher level than humans considered intelligence. Notoriously intelligent chimpanzees, for example, make spears to hunt smaller mammals (SN: 28/02/07). Dolphins carry marine sponges in their mouths to remove sand and uncover prey (SN: 8/06/05). And it is known that elephants threw large logs or rocks over electric fences to cut off the power source.
Studies on the cognitive abilities of polar bears are lacking. “We don’t know anything experimental or objective,” Stirling says. "However, we have a lot of observational information that tends to suggest that polar bears are really intelligent."
Members of the bear family, Ursidae, are usually thought to have strong cognitive skills as a result of their large brains and are evidenced by their sophisticated hunting strategies. Studies on captive black Americans have even revealed some mental abilities that appear to exceed those of primates.
Gabriel Nirlungayuk, an Inuk hunter from Rankin Inlet in Nunavut, Canada, says he heard stories of polar bears using tools to hunt walruses. "I've seen polar bears since I was probably 7 years old. I've been around them, hunted next to them, and seen their behaviors. The smartest hunters are usually female bears." Sometimes, he says, polar bears will trick new seals into approaching by pretending to be sleeping on the ice. Other times he has observed that a polar bear can sniff the breathing hole of an ice seal, even if it is hidden by snow.
“I’ve been working with Inuit on traditional knowledge for a long time and one of my favorite topics is polar bears, because science often suggests one thing and Inuit say something else,” he points out.
There are about 26,000 wild polar bears living in 19 Arctic and subarctic subpopulations. Bears eat mainly seals, hunting marine mammals by protruding above their breathing holes. Due to climate change, Arctic sea ice is rapidly disappearing and scientists predict that many polar bear populations will become extinct by the end of the century. Desperate polar bears can increasingly attack walruses, but “there are limitations to how many walruses an adult bear can carry,” says co-author Kristin Laidre, an arctic ecologist at the University of Washington in Seattle. It takes a lot of energy.
After the publication of the new study, Stirling received a video from U.S. scientist Geological Survey Anthony Pagano, based in Anchorage, Alaska, who had previously connected a GoPro camera to a wild polar bear for a separate project. That image, Stirling says, shows a female polar bear sliding a large block of ice before throwing it into the water on a stamp.