I went to move the chicken tractor this morning, and there were muddy critter tracts all over it. All the birds are ok, but I figure whatever it is, it will be back. I have red heat lamps on to keep them warm at night, so I was hoping that would scare off any critters. It has that white pastic corrigated roofing stuff on 1/2 of the tractor, and "old" chicken wire on the sides and the other half of the top and then one end is closed in with a towel across most of the opening to the closed half to block wind and draft. What else can I do to keep critters away?