I have fences around the perimeter of all residential lots then lock the main gate to keep any wandering foxes from entering. I don't use the fox challenge but have had the occasional fox wander onto residential properties which is why I use fences. I let the chickens roam all over the home lots, and it's so cute when they come over to 'talk' to my Sims as they garden or take care of the llamas. It's a lot easier to maintain a high relationship with the chickens if they're allowed to wander because they tend to follow my Sims everywhere.