Thinking of getting a second, third, fourth dog? Be prepared, your happy household may get turned upset down. Pack dynamics can change very quickly with the addition of a new personality. As a frequent foster mom with my own two dogs, I can personally attest to this, and would not have believed it if I hadn’t experienced it myself.

My dogs are 10-year-old Standard Poodles, Monty and Monet, who I adopted last year. They have very sweet, even temperaments. Monty especially. He’s a docile, happy dog who gets along with everyone. Monet is docile too, however, can be a little bitchy with some other dogs. She can be the “fun police” too, trying to interrupt when other dogs are playing. I have had other foster dogs and even watched friends’ dogs in my home, and Monty and Monet always got along great with them.

Two weeks ago, I agreed to foster Norm, a 9-month-old Basset/Boxer mix. When he arrived, he was so shy and withdrawn. He cowered in the corner most of the first night and ran from me for several days. He spent most of his energy avoiding contact, even with Monty and Monet. But as I worked with Norm and he grew more trusting, his real personality began to emerge. Monty and Norm started to play together. Monty seemed to enjoy the new playmate. Norm often tried to initiate play with Monet as well. True to form, Monet rejected his advances by growling and even chasing him away. I was not surprised by her reaction. But Norm did not take the correction – he continued to try to play with Monet despite her obvious signals.

One morning, Monty and Norm were playing and Monet looked as if she wanted to play too. She followed them around and tried to get in the game. She mimicked their play by nipping at Monty’s back leg. Monty whirled around and went after her. It was not play. She came back at him and in an instant, I had a full blown dogfight on my hands. Monty and Monet had NEVER fought before, always best buddies. Nobody was hurt, thank goodness. I was stunned beyond belief at what I had just seen and very grateful that I had enough sense to keep a close watch in the dogs’ interactions. The presence of a new dog, a different personality, had changed everything.

So if you are considering adding another dog to your household, be prepared for anything. I would suggest you get the name of a highly qualified dog trainer to give advice for introducing a new dog and to help if any issues arise.