If dogs can dig under so can fox, raccoon, rats, you name it. Either dig 2 feet down to bury 1/2 inch hardware cloth around the entire coop and run or spread a 2 ft wide hardware cloth apron. No chicken wire, it isn't made for predator protection, only to keep chickens in. I swear chickens are the only animal unable to rip through chicken wire.and the dogs dug under the fence once they saw the chickens were loose.