It was once believed that walruses dug for clams with their tusks, but the truth is even stranger. It was once believed that walruses dug for clams with their tusks—but the truth is even stranger.

Walrus mothers and calves depend on the moving sea ice to carry them over this rich source of food. But now, as the sea ice melts farther north, if they stay on their platforms, they'll be carried ...