WASHINGTON -- The polar bear is natures largest carnivore, and today it is in trouble.

Its hunting grounds are shrinking as the ice melts in the north because of global warming.

While some debate whether human activity is responsible, photographer Howard Ruby is taking pictures. Huge, endearing photographs of mother bears and their cubs.

He said he hopes it will get humans to stop talking and start conserving the future of these creatures.

"The world will still function without polar bears," said Ruby. "But they are a warning that we are in the process of massively changing the world."

Ruby said he fell in love with the polar bear while traveling in the far north.

Traveling in a tundra buggy, Ruby spent three years photographing the giant beasts. He was able to get within 100 yards of the animals, and captured intimate moments humans rarely see.

"One of the reasons we love this animal is she's so endearing," said Ruby.

His photo's capture that. Some pictures show a cubs youthful exuberance and a mothers understandable fatigue. Landscapes detail glistening bays that should have frozen months earlier, or icebergs with melting pools.

Ruby wants those photos to be a message. He was just named the conservation photographer of the year by the National Wildlife Federation. He's using his platform to educate children.

Recently, Ruby started the Global Warming Crusade. It features cards that detail the plight of the polar bear, and is distributed to school children.

In the meantime, the government tries to decide what to do. A decision on whether to declare the polar bear endangered will be made in January of 2008.