Not all Berners are good guardians. Ours is very friendly and wants everyone to pet her. However, as she grows, her size and forwardness is enough to cause most people to back off. You will definitely know if someone is there. We've had more than one occasion when our young dog snapped to attention in the house and quietly went to the back door. We peeked out the window and found a Pit Bull in the front yard. Loyalty has to be earned. Ours had none until she learned she was not the pack leader. I've met others who have several Berners and they are great guardians. They don't even let the neighbor's horse get within ten feet of the property line.
Answered by lmontague - 12/14/2013 7:24:40 AM