A new pet can be a wonderful addition to your household; but sometimes this good idea can quickly turn into a bad experience. If we do not carefully consider the current make-up of our household, including our other pets, we can find ourselves in an unhappy or stressful situation.
When considering the adoption of a new dog, cat, or bird, there are many important issues to address. I would suggest that you first look at what kinds of pets you currently live with and carefully reflect on how well the two (or more) might get along. If this is to be a happy experience for everyone, the new pet must enrich the lives of not only the people in your family, but also the animals.
The age, sex, weight, and history of the other pets you own can be very important factors in successfully incorporating a new pet. Take the time to consider if your proposed additional pet is a good match for your family; resist impulsive choices. For example, dogs with more than a twenty pound weight difference, or a situation that would require leaving an older dog alone with a young pup, can be problematic and even dangerous.
When introducing dogs to each other, it is best to do so on neutral territory, perhaps outside of your house, at a park, shelter or rescue. Be prepared with great treats to offer both dogs to help them make a positive association with each other. Give the pets the sense that good things happen when they are together.
After the initial introduction it is helpful to take the dogs for a walk together, but make sure that each dog has a separate handler. The distance maintained between the dogs will depend on how well they responded to their first introduction. I like to begin our walk with a person positioned between the two dogs in order to make the experience very comfortable and nonconfrontational. If the dogs seem compatible with each other on the walk, take the new dog inside the home to explore, while keeping the familiar dog outside and distracted.
After a little time for exploring, I would bring the new dog outside and walk the two dogs again; then eventually walk them into the house together. Keeping the dogs on a leash, or separated by a baby gate or fence, allow them to get used to each other in a safe way, while you sit down, relax and observe.
Before bringing a new pet into your home, make sure that you have picked up all toys or things of value to help prevent “resource guarding.” Keep the dogs separated at first when they are in high excitement situations, such as when you are feeding them or giving them a toy. Even your attention or petting can be considered high value (just like a treat), which can cause conflict between new or visiting dogs.
In the past, many behaviorist and trainers recommended that when an owner brought home a new dog, the existing pets were always to be put in first place. The theory was that it was important to promote the first-to-arrive dog in the household as the "dominant or top dog." This was thought to be the best way to prevent or resolve conflict between the new pack members. For example, clients were told that pet owners’ attention and food should be given to the new dog only after the others’ needs had been met, and to have the new dog wait to come inside or walk through doorways after the other pets had entered.
As with many previous theories about dogs, time, experience, and more recent studies have made us reconsider these ideas. Can we decide who will be the dominant dog? Are we giving the wrong message and possibly creating or supporting a bully? With time, the true “pack order” of the house will emerge, and the dogs will figure out which one of them controls which resources. Therefore, I would suggest more equal treatment as the best procedure and that encouraging dominant or aggressive behavior in our first-to-arrive pets is not a good idea. Teach them that they must look to you as the pack leader and you will make all important decisions, including when to sit or what order to come into the house. I like to vary it a lot, which helps owners have control over their dogs in difficult situations.
If you're having problems or not comfortable introducing your pet to a potential new housemate, you should contact a professional: a behavior specialist or a trainer, who can help you with this process.