I currently have a PVC pipe gravity feeder that has worked brilliantly for the last year. Over the last few days something has thrown all of the food out onto the ground. What used to last a few days, was gone within 12 hours today (mostly overnight). I buried a predator apron and have 1/2 inch hardware cloth enclosing the whole run. I saw one mouse last summer, but no evidence of them since. Could mice be the problem or is it probably something else? I refuse to use traps or poison and am looking for some humane prevention methods. Help!