Ian Stirling studies polar bears on Canada's Hudson Bay, where sea ice melts three weeks earlier than it did 30 years ago. The early melt limits the amount of time polar bears have to hunt seals, their primary prey. As a result, bears today weigh less and give birth to fewer cubs than they used to.

"The bears are getting thinner and the population has declined from about 1200 in the mid-1990s to less than 1000 now. If climate warming continues as predicted, there will be serious declines in numbers of polar bears all over the Arctic."

Fat Polar Bear

Female polar bears fatten up before denning, but they don't get fat like this one anymore. (The female in this old picture has a radio glued to the top of her head so researchers could find her den; her neck was bigger than her head, so they couldn't use a collar!)

Skinny Polar Bear

Female polar bears have to live on their fat reserves for eight months, and today's bears weigh 15% less than those in the early 1980s.

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Mountain Plants

Photos courtesy Dr. Ian Stirling