A polar bear

A polar bear bites a mock Easter Bunny stuffed with food at the Buenos Aires Zoo.

Polar bear cub

Polar bear cub Wilbaer swims with his mother Corinna in their enclosure at the Wilhelma zoo in Stuttgart during his first appearance April 16.

27-year-old polar bear

Uluu, a 27-year-old polar bear, eats treats as she plays with a pumpkin jack-o'-lantern at the San Francisco Zoo.

Polar Bears

A polar bear mother and her two cubs in Wapusk National Park on the shore of Hudson Bay near Churchill, Manitoba. A scientific group that advises the government on endangered species has decided that polar bears don't yet need more protection.

Canada's polar bears

A polar bear cub eats a fish as he just woke up after winter sleeping at a zoo. Some of Canada's polar bear populations risk being wiped out within four decades because of climate change and human activity including hunting, the World Wide Fund For Nature warned.

Polar bear cub

A combination of pictures shows polar bear cub Flocke (snowflake) in her enclosure at the zoo in Nuremberg during her first public appearance.

Polar bears

A pair of polar bears nuzzle each other. Thanks to mounting research on wild animals' food needs, today's zoo staffers are trying new feeding tricks to keep their animals healthy and happy.

Polar Bears

A polar bear sow and two cubs are seen on the pack ice in the Beaufort Sea in northern Alaska.