I know they are a pest and one of God's creatures I really have no patience for unless they are on someone else's property and creating havoc underground far away from mine, but can a groundhog harm chickens? ( I was so surprised to hear that possums do!) I am thinking of expanding the run into an area near where there had been groundhog activity last Fall. Short of one of those overgrown rodents building a tunnel under the run or opening into the run, I would be concerned for my (yet non-exsistant) flock. I have an Aussie and a Border Collie mix that have a great system for killing them when they are stupid enough to pop up in the dog's sight line. (I've got a Corgi too, but she let's the boys have their fun since the grounhogs are as big or bigger than she is.) I'm rambling...it's late, sorry. So... groundhogs predator or just a pest?