Mike Lockhart, a biologist with Polar Bears International, was part of a Manitoba Conservation team conducting an aerial survey of the bears of Canada’s Western Hudson Bay late last year when the crew came across an adult male and a smaller subadult feasting on the carcass of a freshly-killed seal. There was nothing unusual about that. What caught the scientists’ attention was the fact that, about 400 meters away, a female with two young cubs was heading straight for them.
Polar bear mothers are often extremely cautious and nervous in the presence of large males, and for good reason. Although cannibalistic attacks are rare, they do happen. As they watched the female make a beeline for the kill, with her cubs perhaps 100 meters behind her, Lockhart and his colleagues braced themselves for the worst. “All of us in the helicopter were sure we were going to see a cub wiped out,” he told Discovery News.
Instead, the mother simply joined in the feast, and, after initially standing back hesitantly, the cubs joined in. The large male is in the top right of this picture. Adult males can frequently weigh over 1,000 pounds, several hundred pounds more than females, and are accordingly far stronger. That a female should place herself and her cubs in such apparent danger was unusual in itself. What happened next was all the more so.
“She was there feeding," recalls Lockhart. "They were all feeding. Then all of a sudden ... she just started batting the male around, pushing him back. She did that several times. He tried to get a little bit closer and she’d keep chasing him off.”
Perhaps, speculates Steven Amstrup, Polar Bears International’s chief scientist, the female could sense that “the male was a bit tentative. It recently could have fed and was not strongly motivated by hunger. Or ... she could tell he was more tentative than other big males might have been when on a kill.” Or perhaps extreme hunger overtook her initial caution before her defensive instincts kicked in. But, while both men add the caveat that judging a bear’s condition from the air is a highly suspect enterprise, Amstrup notes that “although I’ve seen fatter bears, they aren’t emaciated either.”
Remarkably, the cubs even joined their mother’s pursuit of the male. “She moved the big bear quite a ways away from the kill,” Lockhart says. “The cubs initially stayed at the kill, but then they came right up behind her, and they were all hackled up and you could see their lips curled. It may have been just fear. I have no idea. They could have run the other way, but instead they came right to her.”
Amid all the commotion, the subadult bear kept on feeding. “I think he’s the one who made the kill," Lockhart said. "He had a pretty big gut and I think he ate a lot of it. But he never budged. He just stayed there with all the excitement that was going on with the other bears.”
It's not unprecedented for a polar bear mother to shoo away an adult male that she feels is too close. But to actively head toward a kill where a large male is feeding, and then to chase that male away, is behavior that neither Lockhart nor Amstrup have seen before.
“I think what it says is that it may be a question of the size of the fight in the bear rather than the size of the bear in the fight,” observes Amstrup. “A motivated female with cubs might be more aggressive, and males, even though they could kill a female if they wanted to, are probably going to get injured in the process. And so depending on the circumstances, it may be healthier for them to back down. It really is a good example that a female with young can be a pretty impressive fighting force.”