I've owned dogs all my life. Usually multiple dogs at once. We never had a Boxer before but got a 1 year old MALE from a rescue shelter 2 months ago. So we are trying to figure Boxer temperament out. He's a great dog. He LOVES people. We also have a 9 year old FEMALE Visla mix and a 6 year old MALE Chihuahua/Terrier mix. They all have gotten along for the 2 months. They now even play together a lot. There was one time the Boxer was chewing a toy with a treat I put in it. Out of my sight, the other male must have gotten too close. My Boxer attacked the male and had a hold of his neck to the point of bleeding. Everything was fine until this past weekend when a friend brought their MALE Golden Retriever over and my Boxer absolutely attacked him. It was scary. But in hindsight I think we went too fast. Anyway, we are leaving on vacation for a week and are boarding our 3 dogs TOGETHER. We have always done this. However, now I'm starting to worry that the Boxer will attack my little male. They are fine with each other 99% of the time. I'm just worried what may happen when not supervised. Should I be worried?