4/22/2012 1:16:49 PM

Polar Bear Populations Remain on Thin Ice

A drop in the number of cubs and longer and longer ice-free seasons point to a worrisome future for the Western Hudson Bay population of polar bears. Ed Struzik of the Edmonton Journal reports on the reaction of two our Advisory Council scientists, Dr. Ian Stirling and Dr. Andrew Derocher, to a recent claims that the polar bear population there is larger than was thought.

Polar bear on thinning ice
A drop in the number of cubs and longer and longer ice-free seasons point to a worrisome future for western Hudson Bay polar bears. 

EDMONTON — Two of Canada's top polar bear scientists warn that recent attempts to justify an increase in the harvest of the iconic animal in western Hudson Bay could lead to trade sanctions against Canada.

University of Alberta scientists Ian Stirling and Andrew Derocher say the population is neither as "abundant" nor as "healthy" as a Nunavut Inuit organization claimed last week when it used the preliminary results of a recent survey to justify an increase in the annual harvest.

Nunavut Tunngavik Inc. said preliminary results from the Nunavut government survey contradict previous reports by Stirling, Derocher and other scientists who have been tracking polar bears in this region for the past 40 years. They say it also vindicates Inuit hunters who insist there are more bears than ever.

Suggesting that the research was "faulty," as Nunavut Tunngavik stated in a news release, is both "untrue and inflammatory," says Stirling.

"The Nunavut aerial survey estimated the population to be between 717 and 1,430. This aerial survey-based estimate is not significantly different from the 2004 estimate of 934 bears we did, which was based on more reliable mark-recapture studies in Manitoba."

Lost in the debate, says Stirling, is the fact that the polar bears of western Hudson Bay might be producing only 20-50 per cent as many cubs as they did 30 years ago when the bears had a month or more time to hunt seals on the sea ice.

Now that global warming is forcing the bears to spend more time on land where there is virtually no food, females are on average 30 to 40 kilograms lighter than they were in the early 1980s and producing far fewer cubs, say Stirling. Those cubs that are born are now less likely than they were in the past to live beyond two years, the age at which they became independent adults.

That disturbing trend, Stirling notes, is acknowledged in the latest report by the Nunavut government.

"It clearly states that relatively few cubs of the year and yearlings were observed in western Hudson Bay in comparison to the recent polar bear surveys in Foxe Basin in 2009 and 2010."

"The report also acknowledges that average litter sizes were the lowest recorded in recent years amongst the three Hudson Bay sub-populations."

Stirling says he saw this first-hand in November when he participated in an aerial survey of polar bears waiting to return to the ice in western Hudson Bay. In the area between the Ontario-Manitoba border and the Nelson River, he counted 107 bears, but saw only two family groups. Normally, he would expect to see 20-25 mothers with cubs.

"No matter what the size of the polar bear population in western Hudson Bay is, reproduction and survival of cubs are probably no longer high enough to sustain a harvest. In fact, they may not be capable of sustaining an unharvested population."

Derocher says the recent Nunavut government estimate may be inflating the numbers because the aerial survey area is greater than that covered by more accurate long-term mark and recapture studies. It may have also included animals from the southern Hudson Bay region, which sometimes move into western Hudson Bay.

The bottom line, he says, is that the breakup of the ice is already an average of three weeks earlier than it was only 30 years ago, freeze-up is later, and the duration of the open water is steadily increasing. Being creatures that need ice as a platform to hunt seals, a primary source of food, polar bears in this rapidly warming region are extremely vulnerable.

"Canada is being scrutinized internationally for its management of polar bears," says Derocher.

"That's why it's more important than ever to use sound science-based management to justify harvests. This aerial survey cannot be used to assess population trends using any scientific method. Some comparisons are possible, but not from this interim report."

In February, the U.S.-based Center for Biological Diversity submitted a petition to the U.S. Department of the Interior seeking trade sanctions against Canada for violating conservation agreements on polar bears by allowing the continued hunting of the western Hudson Bay bears.

The centre submitted the petition after the Nunavut government raised the polar harvest quota to 38 last October even before the results of this latest report came in.

This isn't the only challenge the Canadian and Nunavut governments face, notes Derocher. Canada's ability to export polar bear hides, he points out, could be in jeopardy at the March 2013 meeting of CITES, the Convention on International Trade in Endangered Species.

"Canada's management has drifted from a precautionary sustainable approach that worked well for the last 40 years to one seeking maximum harvest levels with fewer safeguards. If Canada doesn't move back to this conservative and precautionary approach, the international community will dictate trade to the detriment of Inuit hunters and the collapse of international trade."

Stirling says he has the greatest respect for Inuit traditional knowledge and observations. But he doubts that experts with CITES will accept a point of view that appears to be influenced largely on anecdotal evidence of more bears coming into the communities and hunting camps if it is not supported by scientific data on the size, survival rates, and reproductive success of the population.

"There is no doubt the observations reported by Inuit hunters are accurate, but the reasons for the change, he says, are tied to ice conditions that are causing a long-term decline in the population.

"The earlier the breakup, the poorer the condition of the bears," he says. "The poorer condition the bears are in the sooner they exhaust their fat supplies and come into towns or hunting camps looking for something else to eat. No factor other than climate warming has been shown to be significantly related to the increasing numbers of problem bears, although the local presence of human attractants such as dumps likely contributes to the attraction of hungry animals."

Progress in polar bear conservation can only occur if everyone works together, using information from all possible sources, scientific and traditional, says Stirling.

"Making such inaccurate, incomplete, and misleading statements in a news release, ahead of the completion of a final report that is based on all the information available, is harmful to the collaboration required for successful polar bear conservation and reflects poorly on Canada in the international arena."

Photo copyright Daniel J. Cox/Natural Exposures.

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