For multiple dog households, it seems easy to simply add another and hope everyone gets along. However, dogs form a pack, viewing the home as their territory with you as the pack leader. Drop expectations that incorporating a new furry friend will be an overnight success. Dogs need to sort out their own rank depending on a variety of factors such as age, gender, breed and personality. Learn how to provide a smooth transition for a new dog into the already established pack.
Introduce each of your dogs individually to the new dog on neutral territory, at a local park or a friend's yard, for example. Allow the dogs to investigate each other through a chain fence or screen door at first, with an adult each loosely holding a leashed pooch; baby gates are another helpful barrier between rooms. Move introductions to an area without a barrier if all goes well. Do not force interaction but use vocal praise to help set the tone. Keep the meeting short by walking the dogs away from each other.
Permit sniffing, gentle tail wagging and relaxed postures. Reward this behavior with positive praise and treats. Intervene should either dog maintain direct eye contact, show raised hackles, bare teeth, growl or exhibit an overall stiff body stance; expect disagreements but it should never turn into bullying or full blown aggression. Be ready to regain their attention by whistling, giving a command or walking the dogs away from each other. Take a walk if either is nervous, hiding behind a human to avoid contact with the other dog.
Implement crating, with each dog given his or her own crate, even if your dogs are not used to it. Allow your dogs to individually visit the newcomer in his crate, and then the pack can visit all together. Again, reward good behavior with verbal praise and treats but step in should any dog exhibit aggressive behavior. Remove the guilty party from the room until he or she calms down and have another adult on hand to watch the remaining dogs. Supervise all interactions outside of the crates and return the dogs to their crates before leaving the house.
Order in the Home
Pick up uneaten food after 15 minutes and never leave toys around since dog fights most often occur in relation to these items. Think of it as the food and toys are yours and the dogs are merely allowed to borrow them. Keep plenty of water bowls, however, and places for each dog to relax around the home. Restrict the dogs' access to your bed and furniture as this can be another point of contention; more specifically, do not play favorites. Maintain one-on-one training and interaction with all of your dogs. Training the new dog in basic obedience will further let him know that you are the pack leader.