Polar bears in Canada's Western Hudson Bay — on the southern edge of the Arctic — are continuing to die in high numbers, a new government survey of the land carnivore has found."The actual decline is a lot larger than I would have expected," said Andrew Derocher, a biology professor at the University of Alberta who has studied Hudson Bay polar bears for nearly four decades."Those are the types of bears we've always predicted would be affected by changes in the environment," said Stephen Atkinson, the lead author who has studied polar bears for more than 30 years.Young bears need energy to grow and cannot survive long periods without enough food and female bears struggle because they expend so much energy nursing and rearing offspring.The capacity for polar bears in the Western Hudson Bay to reproduce will diminish, Atkinson said, "because you simply have fewer young bears that survive and become adults.""