Bells are a good idea. Never thought about that. I used to have a mixed breed small dog. She was a protector. If she didn’t know someone, she would go for the throat and then bark. Didn’t know that about her till she was out playing with my daughter and the next door neighbor’s children. She baby set so there were like 5 or 6 children out in backyard playing ball with the dog. A man that was the father of one of the children walked into the backyard and the dog got between him and the kids and lunged at him, right for the throat. I managed to pull her away but he was mad. Tried to explain that she was protecting the kids and she didn’t know if he was there to do harm or what. So after that I couldn’t allow the dog out to play with the kids anymore because of his complaint to the neighbor. I really do miss that dog though. She’s been gone from here a long time and I really would love to find another one like her.