Earth Equity News

In Canada, Grizzlies Invade Polar-Bear Turf. By Michael D. Lemonick, Time, Feb. 27, 2010. "If you want to see polar bears up close, the place to go is Churchill, Man., on the western shore of Hudson Bay. When the ice breaks up in the summer, the bears come ashore by the hundreds to wait for the autumn refreeze. So it's where tourists and scientists go, to gawk at and study the huge white predators. Just south of Churchill, the Canadian government recently created Wapusk National Park (wapusk means 'white bear' in the indigenous Cree language) to protect the area where pregnant females dig their dens. But in recent years, another large predator, not quite as big as the polar bear but equally fierce, has been spotted in Wapusk. Although hunters eradicated them from Manitoba more than a 100 years ago, grizzly bears are trickling back and setting the stage for what could be a fascinating natural ecological experiment. If a reshuffling of the grizzly- and polar-bear populations is nigh, it's not clear where the new lines will be drawn, says Robert Rockwell, a biologist with the American Museum of Natural History in New York City and co-author of a new paper documenting a spate of recent grizzly sightings in the journal The Canadian Field-Naturalist. Before 1996, there had been no evidence of grizzlies in the national park, but between 1996 and 2009, Rockwell says, there were nine confirmed sightings, plus three more in 2009...

"Paradoxically, the intrusion of another top predator could in some ways make life easier for the white bears, says Rockwell. 'Polar bears will eat anything they can get their grubby little mouths around,' he says. 'They'll take flightless geese, seals silly enough to get caught on shore when the tide goes out and caribou and moose calves. But they can't run fast enough to bring down adult moose or caribou.' Grizzlies can and do -- but the catch is, as soon as a grizzly knocks one down, the polar bears will smell it. 'An adult male grizzly might weigh 600 lb. An adult polar bear is more like 1,500 lb. Grizzlies aren't stupid,' says Rockwell. That same instinct for self-preservation will probably mean there won't be many outright fights between the two species… Rockwell says, adding, 'In 41 years in the field, where I sometimes see 200 bears in a day, I've seen exactly one aggressive encounter.' A more likely scenario is that the grizzlies will snatch polar-bear cubs as they emerge from their winter dens or vice versa, says Rockwell. Most intriguing of all is the possibility that the two species might interbreed."