Gnawing leisurely on the remains of a moose carcass, the wolf pack's alpha male seemed unaware that mortal danger was coming ever closer. Suddenly the eight-member rival pack burst into view. The alpha scrambled to his feet, but too late. Howling and barking, the enemy chased him down and mercilessly attacked, killing the hapless victim within a couple of minutes. It's not unusual for the gray wolves on Isle Royale National Park to target each other, said John Vucetich, a Michigan Tech University wildlife biologist who witnessed the carnage from an airplane in January. But the rival pack's brazen invasion...