This photo was taken on the Beaufort Sea north of Barrow, Alaska, on March 27th, 2009. It was 35 below zero and the field biologists had just darted this 1000-lb male polar bear with enough sedative to keep it calm for an hour so they could measure, weigh, and take blood samples. 

Long-term monitoring of polar bears in Alaska will help scientists and managers know what to do as the ice and the seals that polar bears depend on disappear. 

The weight of this fella's head was like a cannon on my legs.  It's so eerie to be this close to such a magnificent creature.  His eyes were open and I could hear him breathe. 

A few hours later he was up and about, carrying on with his life, so supremely adapted to the stark and extreme conditions of the Arctic.