Great horned owls, martens and wolverines are known predators of juvenile great gray owls, while the Eurasian eagle owl is the only known predator of adults. Such attacks on full-grown birds are rare, as the giant great gray is the longest owl species in the world.
The ferocious bird has been known to fend off animals as large as black bears in defense of its nest. Plentiful throughout northern Europe and Asia and also native from Alaska through Canada and down to the Rocky Mountains, its mortality in the wild is often due to starvation. Fatalities are occasionally caused by humans due to electrocution, road kill and shootings.