Do it GRADUALLY.
Here is a useful process breakdown for a successful multi-dog pack integration.
Are the humans ready for it? Having a second dog actually means that everything doubles (or triples!!); cost of care like food and boarding, amount of poop to pick up, vet bills. Bonding with each dog individually is important – whether you have sufficient time should be a key factor in your decision making process.
Would your dog want another dog in it’s territory? Observe your dog in the company of humans and other dogs. For example, when you are out – does your dog naturally veer towards humans or dogs?
If you have decided that another dog would add more joy to both the humans and the current dog(s) in the household, take the time to invite some dog friends over and observe the type of personality your dog prefers. Does it prefer just chilling out with other dog, or does it have a blast with playful and boisterous dogs? Age, gender, energy level and temperament are all things that you should consider in terms of suitability.
Always start with neutral grounds, to see how the dogs respond to each other. Taking a walk together is a good way to get the dogs introduced. Whilst the dogs focus on moving forward, you can change the positions of the dogs – whether they walk in parallel, but separated by the humans, or walking front to back of the other. Changing the positions allows both dogs to download information via scent about the other dog.
Here is the most important thing about integration – do it GRADUALLY and PATIENTLY. You are putting two dogs with different personalities together, and it would take time for them to get to know each other. Take your time. More importantly, let them take their time too.
Just because the first dog resident was initially there, it does not mean that it would be able to naturally lead the newbie in the household. Let them sort out the hierarchy between each other. One would be the leader and the other would be the follower. Like us, not all dogs are natural leaders – let them decide between themselves. Be there to mitigate and advocate if you feel that the situation is getting intense. Under your close supervision, let them sort it out.
All socialization should be done under supervision. Never leave the dogs together, unattended. Keep possible triggers like food, toys, chews away and only bring them out under supervision. At the start, have them understand the main boundaries within the house. This would enable each dog to settle down in their designated safe spot when they need a time out.
Until you are very confident of their relationship and interactions, keep them apart whenever you leave the dogs unsupervised. There is always the option of keeping them separate via baby gates or crates to settle them down.
You will need to observe how they interact during times of high intensity or possible triggers like having someone ring the doorbell. It would give the owners an indication of whether the dogs may turn onto each other in times of frustration or excitement.
If there is only one thing you take away from this article about integration – take away this – do it gradually.