The research team, led by University of Alberta biologist Seth Cherry, points out that this pickiness about territory would ordinarily work to the benefit of females bearing cubs. The mothers-to-be would not have to spend extra energy wandering in search of dens, because they already know where the best dens are located.
Polar bears, which the US Environmental Protection Agency listed as an endangered species in May 2008, have become fuzzy poster children for the some of the ecological effects of global warming – with reason, notes Dr. Cherry.
"It's true the public and media alike may be disproportionately concerned about polar bears" versus other ecological players above the Arctic Circle, he says. "However, there is scientific merit to the hype over polar bears and climate change."
As apex predators in the Arctic, he explains, polar bears sit at the top of the marine food chain. Monitoring their range, movement, and physiology makes them useful barometers for gauging larger environmental changes – in this case, global warming. And because they rely so heavily on the integrity of the food chain that supports them, they represent an early-warning network for changes that may be taking place with links father down the chain.
A US Geological Survey analysis of polar-bear population studies, published in 2010, put the number of polar bears Arctic-wide at some 24,600 animals. Some 5,000 roam the islands making up the Canadian Archipelago. About 11,900 animals are spread along the continental coasts open to the Arctic Ocean. Some 7,700 live around bays and basins where all the sea-ice tends to be seasonal, instead of a mixture of seasonal and multi-year ice. Hudson Bay falls into this category.