A reader asks:

Two weeks ago we adopted a 6 year old female border collie/spaniel mix from our local animal shelter. A month before the new dog came along we had to put our 12 year old english setter down. My husband and I thought another dog would be company for our other dog, a 12 year old female springer/brittany mix. Both dogs have been spayed. Recently these two have gotten into some nasty fights. It seems like these altercations happen when they are in close proximity of each other. My husband and I have a difficult time breaking them up and we’re wondering if there’s something we can do to stop the fighting. Both are very nice dogs and it’s only at these trying times that we wonder if we made the right decision to bring another dog into our house. Help!

It sounds like the new dog wants to become the dominant member of the pack. It can take time for them to adjust and figure out who is the alpha dog. You may need to be sure you are sending out signals that you are the ones in charge by eating first, going through doorways first, etc., which can reduce their need to worry about dominance. Also, see if the shelter is willing to offer some assistance or knows of a local behaviorist that can help you. They want things to work out as much as you do.