In a cat care guide book it is strongly adviced never to let a Maine Coon run free, because these cats are very effective predators and run a very large territory. I have no plans to let my Maine Coon run free in the nature, but this advice made me curious. How large is a "very large" territory of a mere domestic cat?

For comparison, when we let our two shepherding breed dogs out alone, with no supervision, they roam an area of roughly 200 yards radius around the house. We don't have neighbours nearby.