Last year PBS ran a documentary about the wolves in Yellowstone. In the latter part of the film something very strange happened. A group of mysterious black wolves came from some unknown location outside the park, and set up a siege, surrounding several dens where females from one of the park's relocated packs had just whelped. The black wolves didn't attack, they just defended their positions and prevented the males from bringing food to their young, waited until all the pups were dead, then left Yellowstone just as mysteriously as they had come.
If you find this fascinating, here's a fuller description along with my thoughts on why this may have happened. Siege at Druid Peak.
LCK