A look at how beavers and wolves interact changing the water and how loons, owls, moose, bears and millions of people depend upon these lakes many take for granted.
How winter has shaped life in the Great Lakes; a polar vortex paralyzes fish and ducks attract hundreds of bald eagles while wolves hunt a deer trapped by ice, but are manipulated by ravens.
These five giant lakes drain a massive watershed bordering Canada and the United States which contain 20 percent of the world's surface freshwater.