Walrus: Life on Thin Ice

For Kirk Johnson, a paleontologist with the Smithsonian National Museum of Natural History, the walrus has been a creature close to his heart for 40 years. Most of the world's walrus, 250,000 of them, live in the frigid seas between Russia and Alaska. Johnson embarks on an Arctic quest to uncover the lives of these enigmatic giants and the threats they face as the sea ice melts. From NATURE.