by Roger Armstrong
Folio Staff

Dr. Ian Stirling has been researching polar bears in the vicinity of Churchill, Man. for more than 20 years. He's found that while polar bears on the western side of the Hudson Bay are traditionally bigger and more productive than other polar bears, these differences have been declining. "These are bears that were very, very fat before and had by far the highest reproductive rates of polar bears anywhere in the world," says Stirling.

Over a 20-year period, male bears have lost 80-100 kilos and females half as much. Despite this loss of weight and declining reproductive rate, the population has remained roughly the same at about 1,200 bears and the new rates are similar to other polar bear populations in the Arctic.

Ian Stirling deploying a radio collar

While the Hudson Bay polar bears are not in danger yet, the trend is clear. If it continues in this direction it will become problematic, says Stirling. Hudson Bay is one of the least-known bodies of water in North America. Over the past 30 years, western Hudson Bay has warmed by 1.2 degrees Celsius. This small increase means the ice breaks up approximately two weeks early, and that means the bears do not have as much time to feed on their main diet - ring seals. This springtime feeding is the most important thing in a polar bear's life, says Stirling. While the western side of the bay is warming, the eastern side is displaying a cooling trend. In western Hudson Bay, "the data are pretty clear that you have long-term climate warming. Whether or not it's part of the long-term natural fluctuation, or whether it is influenced by human activities, is a separate question," says Stirling.

In Hudson Bay, the last ice to melt does so on the coast of Manitoba and Ontario; the bears in the bay are then left on shore for three to four months of the year. "It means the whole population is accessible to you in a fairly small area and they are fairly easily defined - you're just looking for large white blobs on a snow-free earth background," Stirling explains. This is one reason Churchill is such a popular tourist destination, he says, and sometime the bears go right into town. In order to keep humans and polar bears apart, Churchill has built a holding facility for the polar bears as they gather in late October to wait for the bay to freeze.

"We found that they can turn on their ability to go into hibernation-like physiology any time they need to," says Stirling. A grizzly bear will starve to death in a week to 10 days if it has no food during the summer, but polar bears operate more efficiently. When they are ashore in July and early August they do not feed for months - they just switch their metabolism over. Stirling's colleagues at the University of Illinois are looking into applications in human medicine of this ability to change metabolism.

January 15, 1999

With pictures of polar bears on his office wall, a polar bear calendar, polar bear stickers on his filing cabinet and polar bear wallpaper on his computer, it's obvious Stirling has a love for the big white animals.

"I was originally interested in polar bears 25 years ago as predators of seals, and it was not long before I got interested in them in their own right," he says. "The thing that interested me most about polar bears is how they have evolved to live in a very harsh and variable and often unpredictable environment so successfully and apparently so comfortably. You never see a polar bear looking like someone waiting for a bus when it's 25 below."

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