So you have decided to add a second dog to your household. It might have been a tough decision, but you found the right dog. Congratulations! Now you are committed to making it work. It's important to start things off right and allow the dogs to be properly introduced. Then, it can take weeks for the two dogs to get used to one another. Here's how to introduce your new dog to your current dog.
Start on Neutral Territory
The first few times your current dog meets and interacts with the new dog, it's best to be on neutral territory. This works best if you have the help of another person, but you can still do it alone. Take the dogs (separately) to a neutral place like the park. Make sure there are no other dogs around, as this will be distracting. Allow the dogs to meet each other through a barrier if possible, like a fence. Avoid having them on-leash, as pulling on the leash can increase anxiety and even feelings of aggression.
Keep these interactions light and positive. This means you should stay calm, relaxed, and upbeat. Reward the dogs for being relaxed and upbeat. Watch body language closely. If you notice signs of anxiety or over-excited behavior, the session is over. If the dogs remain calm, you can eventually allow them to meet without the barrier. Just remember to separate them at the first sign of tension. Also, make sure play does not get too intense, as this can quickly switch to fighting.
Keep Them Separated
When the two dogs are in your home, it is important that they are kept separated until they have become acclimated to one another. The dogs should have crates or rooms that keep them from seeing one another. They should be fed in separate areas. Each dog should get adequate attention from you away from the other dog. This includes training sessions, which should be frequent.
As the dogs become more used to each other in their neutral territory meetings, you can allow them to see more of one another in your home. This is a good time to put up baby gates. Reward each dog for calm, relaxed behavior around the other dog.
Supervise All Interactions
You may never be able to trust these two dogs alone together, and that's okay. Though many dogs can eventually be left alone together, you should not let this happen for a long time (at least the first few months). Once you get to the point where the dogs are ready to interact freely in your home, be sure you are there to supervise. Observe the chemistry and body language, separating the dogs if you have any doubts. Always do your best to remain calm and upbeat. Make sure there are plenty of toys to go around but remove those toys if they become the source of tension between the dogs. You can eventually feed the dogs in the same room as long as they do not begin to fight for this valuable resource.
No two dogs will have the same relationship. Your current dog and your new dog could become best friends within a few days. Or, they might simply learn to live with one another after many, many months. Chances are, your dogs will fall somewhere in the middle. It will probably take a few weeks for them to accept one another, then maybe months to become trusted companions to one another. There will probably be some power struggles, displays of jealousy and other undesirable exchanges. This is all normal as the dogs are figuring out their places and testing one another's limits. The processed can be a bit like sibling rivalry. If things are not going well, it doesn't mean it never will. Just take it back a step and be patient.