There are several important steps to successfully and safely introduce a new dog into the household. First, it is important to take into consideration the personality of the dog already in the home. Do they want a companion? Are they dog friendly and dog social? How do they typically greet other dogs on walks or at the park? These bits of information can help tell you if and how we should introduce a new dog into the house.
It is important to get the dogs used to each other on neutral ground before trying interactions in the home. Baby gates, exercise pens, and sturdy dog crates are necessary for preventing any greetings too soon.
Start with a walk on neutral ground. Have each dog on a leash with a calm, relaxed adult handler. Keeps the leashes loose; tension on the leash can communicate anxiety to the dog, which can cause them to become anxious or fearful about the other dog. Walk with a safe distance between the dogs, down either side of a street works well. Walk in the same direction for a bit before crossing paths and turning. This allows the dogs to smell where the other has walked.
If everything goes well, no barking, snapping, pulling, or other tense behavior; proceed with allowing the dogs to meet. It is best if they do not meet head on. We can facilitate a more correct greeting by encouraging them to walk circles with each other or even just slowly decreasing the distance while walking parallel. It can be VERY helpful to have another person present to simply observe the body language between the dogs, especially if either handler is unsure what to look for.
If the dogs have not shown hostility when meeting and everyone is relaxed, it is time to take them to an enclosed area, drop their leashes, and give them some space so they can get to know each other. Human interference at this point is only necessary in a few circumstances. If the dogs become overexcited in their play, we can help by asking them to settle or separating and walking them apart a moment until they relax. Or, if one dog becomes overbearing or ignores correction from the other. Then we can step in and calm the situation or remove the offender for a few moments. Otherwise just step back and give gentle verbal praise for appropriate and social play.
Important body language to watch for: Tension in the face/lips. Leaning far forward over the front feet. Hair standing up along the back/neck. Direct, sustained eye contact between both dogs. These are all signs of tension or anxiety. If this body language is present during greetings, it is best not to continue without the help of a dog behavior professional. Dogs with relaxed wiggly bodies, who glance at each other then turn their heads, and paw or play-bow to each other are calm and ready to interact. Praise this behavior and enjoy watching them play.
Remember, some dogs are very vocal during play. While all that growling, barking, and snorting may sound like a problem; it is important that we ignore the noise and keep a close eye on the body language. So long as both dogs are happily enjoying themselves, the noise is just that, noise.
Once the dogs have successfully interacted on neutral territory, it is time to start integrating them together in the house. Pick up any high value toys or chews and put the beds away in a closed off part of the house. The greetings in the home should be done the same as the neutral ground meetings. This way if either dog shows signs of territory aggression or resource guarding, it is much safer to separate them. If they greet well on leash in the house, drop the leashes and allow them to play.
Monitor all interactions in the home closely, especially when adding back the toys, chews, and beds. Remember, it takes time to learn to live with a new family member. We can help keep tensions down by management of resources. Ensure there are more than enough to go around and no one dog hoards or guards valued items. If certain things are highly coveted, they are best given when the dogs are easily separated into rooms or crates.
If there is more than one resident dog in the home, take the time to do a separate introduction as outlined above with each individual dog, both on neutral ground and in the house. Slowly bring them together starting with the most easy-going of the existing family.
The most important part of this process is to TAKE TIME. When we work at a pace where the dogs are comfortable, the results are better and longer lasting. Also, not all personalities are meant to live successfully together. Do not feel bad if it does not work out.