The Evaluation Process
I suggest that you test the new dog with your current dogs one at a time. The steps below should be followed closely.
Start with both dogs on a leash and at a long distance apart. When both dogs are calm, slowly move the dogs closer to each other. When one of the dogs react, make a note of the distance. Correct the dog that reacts. Say “NO” and move back and away so the dog can calm down. Wait for it to be completely calm.
When calm, give the dog a small treat or praise it for being calm. The point of this is to show the dog that good things happen when other dog(s) are near.
It is noteworthy to mention, that getting the dogs together may take some time. Not all dogs will be able to get together in just one session. In the past, it has taken me up to a week to get two dogs together.
Once the new dog and each of your current dogs get along together separately you can move forward.
The next step is to get all three of them together. Follow the step above again. You are going to need another person for this.
All three dogs must be watched closely. You need to know which dog is triggering any aggression. If this is the case you will need to address that.
Continue this until they can sit together quietly.
WARNING: this can take weeks! It may also only take a few hours.
If the dog is just excited, it will take less time. On the other hand, if it “wants to kill” you will need to get some help from an animal behaviorist.
Contact A Better Dog4U if you have any questions or if you need any help with your training. We will be glad to set up a personal consultation in order to help you any way that we can.