When you decide to add a new cat to your home, it’s normally more exciting for you and your family than it is for the cat you already own. That's because most cats are solitary by nature. However, most will also come to accept or eventually tolerate any additional pets introduced into their home. Keep in mind that cats are very territorial, which is why you should always be careful when you introduce a new cat to your current cat. You should definitely expect some initial incidents and unwanted behavioral displays by the first feline.
If you are introducing kittens to one another, the entire introduction process can be short, lasting as little as 10 to 15 days. Introducing cats to each other depends on their individual temperaments and personalities. When you introduce a new cat to your current cat, you should always make sure that you give your current cat plenty of love and attention, and in fact, extra whenever you can, as this will help him realize he is NOT being replaced. All the additional affection and attention you can give the first cat will help him to continue to feel secure and know that he isn’t in competition with your new cat for affection. When you bring your new cat home, you should let him stay in a safe room until you have finished introducing the cats. Do not leave the cats unattended until you have completed the introduction process. Your safe room can be any small room in your home, such as a bathroom or spare bedroom. The key here is to use a room that your current cat doesn’t go in or has not become attached to, as his own "personal" space. In the safe room, you should leave your new cat a scratching post, bed, water dish, litter box, and food dish.
At first, your current cat may howl and hiss when he stands at the door to the safe room, trying to tell the other cat that he doesn’t belong. When this happens you should ignore it, as punishing your cat for his behavior will only lead to more problems. Your current cat's behavior is a natural response to intruders, as cat's are territorial, so punishing him for this reaction will confuse and anger him further. Gradually, the first cat will start to act calmer when he is near the new cat’s door. As he begins to gradually relax and remain calm near the new cat's door, you should pet him and give him praise. This will help him understand that the new cat is not a threat and that his acceptance of the new feline makes you happy.
When your first cat starts to go by your new cat’s door and doesn’t howl or hiss; you can then start introducing them to each other. The best way to do this is to get them used to each other's scent. You can start letting them eat out of the same food dish, although you’ll want to feed them at different intervals at first. Feeding the cats separately this way, with the scent of each cat present in the one food dish, will allow both cats to get used to each other without pressure. This generally works, but on occasion your current cat will refuse to eat out of the same dish. If this happens, simply allow each to have their own food bowl.
Once both cats have gotten used to each other's scent, you can begin to feed them closer together. To do this, you should keep your new cat in the safe room with the door closed, and your first cat on the other side of the door with his food dish. This time, feed both cats at the same time. After doing this a few times, it will become clear to each cat that the other does not want their food because they have their own. The two cats should start eating without any hissing or growling. At this point, they are ready to be introduced to one another.
When you introduce them to each other in the same room, a bit of growling and hissing is to be expected. Although the two cats may be used to each other's scent; your first cat will still feel a bit awkward with your new cat being in his territory. You should play with both cats at first, so they can smell and greet one another in their own way. If they start to fight you should break them up, and give them some time apart. You may have to do this several times before their personalities no longer clash.
It may take some time to get them fully used to one another, although once they do, they will become playmates. Cats love to be social, although it may be a bit rough at first, especially for your first cat. Once they come to fully understand each other's personalities, things should be fine. The key is getting them used to each other early on.