The bears will tear down about any fence up. We haven't lost any to bears since we put an electric fence. We have lost 7 in the last week, but finally found the culprit. It is a big bobcat. We aren't quite sure how we are going to get him yet. I don't know if he is getting them during the day or night. They are locked up in their pen at night, but the door to the coop doesn't close. He may be getting in by climbing a tree and jumping over the fence.