The polar bear cub twins Aleut and Gregor

The polar bear cub twins Aleut and Gregor enjoy the outdoors  in Nuremberg, Germany.

A polar bear looks up at guests aboard Lindblad Expeditions National Geographic Explorer

A polar bear looks up at guests aboard Lindblad Expeditions National Geographic Explorer in Arctic Norway

Vitus, an 18-year-old male polar bear, shakes off water

Vitus, an 18-year-old male polar bear, shakes off water

A polar bear shakes his body to remove water at St-Felicien Wildlife Zoo

First place, Pictorial, News Photographers Association of Canada Pictures of the Year. A polar bear shakes his body to remove water at St-Felicien Wildlife Zoo in St-Felicien, Quebec March 6, 2008.
Credit: REUTERS/Mathieu Belanger

A male polar bear carries the head of a polar bear

A male polar bear carries the head of a polar bear cub it killed and cannibalized in an area about 300 km (186 miles) north of the Canadian town of Churchill in this picture taken November 20, 2009. REUTERS/Iain D. Williams