Polar bear mother with cubs in Wapusk National Park, Manitoba, Canada

It's Polar Bear Day!. Polar bears

Perhaps no other creature is as emblematic of climate change as polar bears, the apex predator of the Arctic Circle. As the planet warms, their fragile habitat shrinks.

In the autumn, as ice floes diminish making hunting more difficult, a pregnant female will dig a maternity den, usually in a snowdrift. She lies dormant there through the winter, giving birth sometime between November and February. The cubs are born blind with only a light layer of fur. In the cold Arctic winter, the newborns remain in the den, growing rapidly on their mother's fat-rich milk until the young family breaks open the entrance sometime in early spring.

This mother and her cubs are enjoying a spring day in Manitoba, Canada, in Wapusk National Park. Wapusk is one of the largest polar bear denning areas in the world and is critical to the survival of about 1,000 bears, a fitting place to mark International Polar Bear Day.