I have about 6 acres fenced to be dog & coyote resistant. It's only 4', but secure at the bottom. If one wanted to climb over they could, but they haven't so far. The coop is not near the fence line, so night time predators that may walk the fence aren't close to where the chickens sleep. I've had 2 predator deaths in 3 years, one was neighbor dogs before we put the fence up, the second was a year later at dusk - a pullet that always wandered off by herself because she was bottom of the pecking order. I don't know what got her, feathers scattered inside the fence but no body, so had to be something big enough to carry her away. I'm thinking bobcat, but what ever it was never came back. I'm surrounded by literally a million acres of national forest, so we have every predator you can imagine. I name my chickens but they aren't really pets: 16 + a rooster - and I know my chances of a complete slaughter are higher here than anywhere, but seeing these guys roam and peck and scratch to their hearts content is beyond joyful. Be prepared as best you can for loss, put up the very best perimeter fence you can afford and learn all you can about your local wildlife. Dogs will usually be the biggest problem if you are in a neighborhood. All that said, if you can't stand the thought of loosing one of your flock to a predator, just build the largest run you can.