I checked a stretch of fence through the woods yesterday that hadn't been used in a couple of months, and a lot of the plastic insulators looked as of they had been whittled away; most will have to be replaced they are so badly damaged. I assumed it must be some creature, but I had never had this happen before. I've seen unused insulators be out for years and stay the same. What could this be? Are squirrels known to chew on plastic insulators?