I think I may have future escape artists! My hens are digging holes in their run right up against the fencing 1-11/2 ft deep. I am afraid eventually they are going to make their way out. I keep filling them in...put a couple bricks in them..they just dig around them. Is this just a way to pass some time or they on a mission to freedom. They do run free several times a week for an hour or so if someone is there to supervise. If they get out when we aren't home I'm afraid they will be goners. We have HUGE hawks and stray dogs. Any suggestions?