EDMONTON Rules that protect female polar bears from being overhunted could make it harder for them to find a mate and eventually lead to a dramatic decline of the iconic animals' population in Canada, according to new research.
A team of University of Alberta researchers issued the dire warning yesterday in a study published in the British-based Proceedings of the Royal Society journal.
"Males may eventually become depleted too far and run into trouble," said Peter Molnar, the study's lead author, in an interview.
He added that breeding success drops quickly and sharply if a critical threshold in the male-to-female polar bear ratio is crossed.
The future of the polar bear is already the subject of a major debate, as many scientists argue that the massive predator is at risk, while Inuit elders vehemently disagree and say the hunt for them should go on uninterrupted.
Nunavut is home to a large number of the approximately 15,400 wild polar bears in Canada.
About two-thirds of the world's 20,000 to 25,000 polar bears are located in the Canadian North, including all three territories as well as Manitoba, Ontario, Quebec and Labrador.
The Nunavut government sets a quota for how many polar bears can be killed each year. (Provinces and territories are responsible for deciding rules surrounding harvests. At least one, Manitoba, doesn't allow polar bear hunts.)
In Nunavut, each community receives a certain number of hunting permits from the territory, which are known as bear tags. A sex-selective harvest policy requires that more males (boars) than female (sows) be hunted.
Mr. Molnar said such policies have reduced the number of males relative to females.
He estimated that about two-thirds of the bears hunted in the Canadian Arctic are males.
Using mathematical formulas and polar-bear population statistics provided by the Nunavut government for the Lancaster Sound area, the researchers constructed models that predicted how many males and females are needed to maintain successful mating.
He said that there is a concern that a lack of males might eventually lead to reduced fertilization rates and subsequent population decline, especially in places where fewer bears are travelling in a larger area.
The study, which was conducted in collaboration with a Nunavut government scientist, found that because polar bears are solitary, non-territorial animals, mating is already tricky because locating a partner can take time. Males normally find females by following their tracks in the snow.
Jim Noble, chief operating officer of the Nunavut Wildlife Management Board, said the study's findings aren't a surprise.
"It's on the radar. We know it is a concern," he said. "We are trying to manage [the polar bear] as conservatively as we can, and yet enable the Inuit to use that resource."
The independent tribunal based in Iqaluit recommends wildlife management strategies and hunting quotas to the Nunavut government.
He said it's currently difficult for people to go against the territory's sex-selective harvesting policy because a community can lose a certain number of hunting permits if they overhunt females during a season.
Polar bears are not considered under imminent threat of extinction in much of the Canadian Arctic range, but wildlife experts in the United States and elsewhere are worried that climate change is starting to threaten population levels because of shrinking sea ice, so they want hunting reduced or banned.
The U.S. government is even considering listing the polar bear under its Endangered Species Act, which would then effectively cripple the sports hunting industry in the Canadian North.
Craig Welsh, a spokesman for the Nunavut Department of Environment, said no government officials were available yesterday to comment on the new research.
However, he said the government is open to reviewing anything.
"We gather every ounce of scientific information that we humanly can when we are putting together policy like this," Mr. Welsh said.
COLD, HARD FACTS
TEN KEY DETAILS
ABOUT POLAR BEARS
1 The male weighs 410 to 720 kilograms and is almost twice the size of the female. Males grow about 2.2 to 2.5 metres tall.
2 With a 10-centimetre layer of blubber under the skin, they are better-adapted to cold weather than warm, and quickly overheat when running.
3 DNA analysis has confirmed that a bear shot by a U.S. hunter in the Canadian Arctic last year was a half-polar bear, half-grizzly hybrid.
4 They are the world's largest land carnivores and have no natural predators. Most of their deaths are from human hunters.
5 During severe Arctic storms, a bear will dig out shelter in a snow bank and curl up in a ball.
6 An adult bear can consume as much as 45 kg of blubber in one meal.
7 They are excellent swimmers and supplement their regular diet of seal with the odd beluga whale.
8 In the wild, females can live as long as 32 years, and the oldest known male was 28. In captivity several polar bears have reached the age of 35.
9 Polar bears do not hibernate. Pregnant females only hole up in a snowbank den in winter for shelter, to give birth and nurse the cubs.
10 Biologists estimate there are 20,000 to 25,000 bears living in the circumpolar North, with about 60 per cent of those in Canada.
Sources: Polar Bears International, Encyclopedia Britannica, National Geographic
BIOLOGY THE BEARS AND THE BEES
Mating season occurs between March and June when the female enters a prolonged estrus. Females generally breed for the first time around the ages of 4 to 5, males one to two years later.
Female bears tend to stay in the area near where they were born, whereas an adult male may travel hundreds of kilometres across the frozen tundra before meeting his mate.
Ian Stirling, a polar-bear expert with the Canadian Wildlife Service in Edmonton, says polar bears require an extended mating ritual to reproduce. To avoid wasting their eggs, females ovulate only after spending several days with a male, Dr. Stirling explains. "Then they mate several times over several days." After a week or two, the male and female go their separate ways.
Sources: Polar Bears International, Encyclopedia Britannica, Canadian Geographic