Whether this is a first time pet or a new addition to an already existing four-legged family, adjustments must be made.
The main thing to remember is to be patient with your new addition. Just imagine if you were a puppy or kitten who has been with your mother and littermates for 8 weeks, and all of a sudden they have vanished. You are moved into a strange house, with strange smells and people you’ve never met before. It can be very intimidating for an animal. While they will adjust to their new surroundings, it may take a little time. Extra love and attention will help make the transition easier.
You will want to take it slow when introducing a new pet to the house itself. Too many rooms too fast can make it a scary place. Start with one room (the one that “belongs” to them). If this is a kitten, make this the room where the litter box and food and water will be. If this is a puppy, this room is where the kennel should go, as well as the food and water dish. You may also want to have a bed and some toys in this room. This will make the pet feel more comfortable and less threatened. As the pet becomes comfortable in this area, begin adding to the amount of space the pet has access to, one room at a time. Remember, this could take hours, days, or even weeks. Every pet is different.
If you are introducing a new pet into a home that already has pets, again, the introduction needs to be slow and supervised. Never leave pets alone that are unfamiliar with each other. I recommend beginning with the new pet (cat or dog) being in a crate or carrier. This serves 2 purposes; it keeps the pet confined so they will not be afraid and will feel safe, and it is less intimidating for the already existing pet. Allow your pet to sniff the new arrival and become acquainted through the carrier. You will more than likely hear some hissing, growling, or see fur sticking up. This is your pet’s way of telling the newcomer that they are in your pet’s territory, and helps to establish ranking in the household.
After they have had a chance to become acquainted through the kennel, and seem comfortable, it is time to introduce them face to face. Again, this should be a supervised introduction. Hold the new pet so they will not seem threatening or jump on the existing pet. Also, be sure to give both pets an equal amount of attention so jealousy will not be an issue. Treats and praising go along way at keeping the peace. Once they are content with you holding the new pet, they may be permitted to be down with each other, under your watchful eye.
The main thing to remember is not to expect too much too quickly. It is a big adjustment for both the new pet and the existing pet. Eventually, things will calm down and fall into place as you had hoped.