An analysis by two of Canada’s leading polar bear researchers says the Western Hudson Bay polar bear population, estimated at 935 animals in 2004, could reach a point in 25 to 30 years where there are too few animals to sustain a breeding population. University of Alberta biologists Ian Stirling and Andrew Derocher said the increasing length of the ice-free season on Hudson Bay will soon reach a tipping point where 20 to 30 percent of the Western Hudson Bay polar bear population will begin dying off 
every year. The polar bears use sea ice as a feeding platform to hunt ringed seals, which provide nearly all of the bears’ annual calories, so rapidly melting sea ice has meant a steady decline in the average weight of polar bears. That weight loss in females has led to a decline in the weight and number of polar bear cubs. After doing a mathematical analysis of the decline in sea ice, polar bear body mass, and fertility, Stirling said, “We can say with a very great deal of confidence, sadly, that the Western Hudson Bay population will be non-viable within 25 or 30 years.” That population is one of the world’s most southerly and researchers have predicted it would be one of the first to disappear as the Arctic warms. An estimated 20,000 to 25,000 polar bears exist worldwide.
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