I think an elk ranch is just like real estate of any kind: location, location, location.

So in some areas, 400-500 acres might be enough. However in most, I would think 1000 acres would be a minimum.

Smaller ranches, even just a couple of hundred acres, might be enough if they backed up to public land that was hard to access except through the private. A smaller ranch surrounded by private, especially in the lower country south of Durango, would not be ideal for year round elk. Elk just are too moble Deer, yes, but not elk