Whereas the Gray Wolves now reintroduced into their former ancestral habitat of Yellowstone National Park rely on the area’s population of North American Elk (Cervus canadensis) to provide their primary source of food, in Isle Royale National Park, it’s Moose (Alces alces) that sustain the pack. However dietary differences aside, both wolf populations have and continue to face challenges to their existence – both natural and human directed.