We have a neighbor dog that comes over to the chickens run area and we do really have to watch him when he is off running loose. That said, he has dug under the run area and pulled up the fencing at the bottom in several different area just to get into the run area. He's some kind of Shepherd that is a hunter. He hunts the rabbits, squirrels and can jump into the air to catch birds, he has also brought his catch to his owners. He seems to come around most of the time when I give the hens people food. Dog does not get any human food what so ever so this is his way of trying to get something that he normally doesn't get at home. He never got into the run but he has got to close to the fencing one time and one of the hens almost pecked his tail, it would of if the dog didn't move. I think he is just interested in what the hens are eating when he visits and wants it!!! We do have him under control since he listens to us when we tell him to go home, he is pretty good other than digging under the fencing.