It's very important to introduce a new animal into your home in such a way as to cause the least stress and disruption for the new pet as well as your existing fur family. Sounds like a no-brainer, right? You'd be surprised how often people don't follow the instructions given by their adoption counselor. And then we see the animal returned because it "couldn't get along" with their other pets.
**disclaimer: this is my opinion/based on personal experience. I'm in no way speaking for or on behalf of the shelter**