Thursday, December 17, 2015

Wolves take down polar bear near Hudson Bay

Evidence suggests part of pack distracts mother bear while others drag cub away
By Martin Zeilig, for CBC News Posted: Dec 15, 2015
 
A Manitoba Conservation official has seen evidence of wolves successfully hunting a polar bear cub near Hudson Bay.
A Manitoba Conservation official has seen evidence of wolves successfully hunting a polar bear cub near Hudson Bay. (Cameron MacIntosh/CBC)

A Manitoba Conservation official has found evidence that wolves near Hudson Bay have learned to hunt polar bear cubs.

Polar bears are generally considered the top of the Arctic food chain, but a pack of wolves apparently distracted a mother bear long enough to take her cub in the Kaskatamagan Wildlife Management Area in northeastern Manitoba, said Daryll Hedman, the wildlife manager for the province's northeast region. "This is the first strong indirect evidence I've ever seen of wolves preying on a polar bear cub. They probably killed the cub and dragged it away. There were, perhaps, three or four [separate] wolf tracks," Hedman said in a telephone interview. "This doesn't happen often. It still seems to be a very rare event."

Hedman, who has been conducting polar bear maternity den emergence surveys in the region by helicopter for four years, has heard of such encounters before, but he saw evidence of such an attack for the first time in March. "We've had reports of wolves predating on polar bears [the cubs] in the past by lodges and First Nations, mostly when the polar bears are coming off the ice onto land at the end of July," said Hedman, who is based in Thompson, Man.

"In our most recent report, a First Nations trapper reported to me what looked like a polar bear-wolf encounter" in the wildlife management area east of York Factory on the Hayes River, which runs along the Hudson Bay shoreline to the Ontario border. He said a single adult polar bear track was leaving the den site. About five days later, we were doing our survey by helicopter. We landed [at that site] and there was definitely evidence of polar bear and wolf tracks."

Churchill MB polar bear Nov 2015 in the grass
Members of a wolf pack get a mother's attention, then the rest of the pack grabs her cub, Daryll Hedman says. (Cameron MacIntosh/CBC)

A single polar bear track led away from the site where the encounter was reported to have taken place, Hedman said. "There was also a single cub track leading up to the wolf encounter, and after that, only the single track of a female polar bear going out to the ice of western Hudson Bay," he said.

The polar bear cub was probably four or five months old, Hedman said. "I've had reports from people who have actually seen this sort of thing before," he said. "What will happen is the female polar bear can't react quickly enough when the wolves are in a pack. Some of the wolves are getting her attention and the others go for the cub."

Other scientists and researchers have also seen evidence of wolves hunting polar bear cubs. "In 1983, the late Malcolm Ramsay and I found evidence of a pack of wolves in the Churchill denning area that had learned to kill polar bear cubs when they were on their way to the sea ice from their maternity dens," polar bear specialist Ian Stirling wrote in his book Polar Bears: The Natural History of a Threatened Species. "Tracks in the snow revealed that some wolves would worry and distract the mother while another seized a cub and apparently escaped with it. The cubs were completely devoured. In more recent years, wolf numbers appear to have increased since the area became a national park."

In most areas, the distributions of polar bears and wolves do not overlap very much, Stirling wrote. "However, where they do, some wolves are learning to become successful predators of polar bear cubs, though it is probably not a common behaviour."

Hedman also emphasized that this is a rare occurrence. "It happened right on the tidal flats of Hudson Bay," he said, noting the area contains a pretty healthy population of moose, the main prey species for wolves along the Hudson Bay coast in Kaskatamagan. "Where the polar bears den, there are no wolves, but once they leave the dens and get closer to the coast, they might encounter wolves."

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