When I decided to adopt my new cat Angel, I knew I would be facing some different challenges than I had with our previous additions because of Angel being an older cat who had never lived with other cats. True, I had adopted Jackie at around 11 years old but only my dog Abby was in our home at the time, and it was an easy transition because Jackie was used to other animals from being at the Humane Society for so long. And Gidget and Lola were both young when they joined us and blended in very quickly.
So I looked for some advice on handling Angel's homecoming to make the transition as easy on her and our 2 cats and 2 dogs as possible. I found a lot of information on bringing home a new kitten, but very little for an older cat.
First and foremost, confine the new cat to a quiet room or area that can be sealed off so that the other pets cannot enter. Place the cat's food, separate litter box, bed and some toys in this room. Plan on the new cat staying in this room for 10 to 12 days. The separate room is important so that both your existing pets and the new cat feel secure without having to come face to face, and also to quarantine the new cat until you can take him or her to the vet for a checkup.
Angel got used to all of us and our home much quicker than I anticipated. One of the things I did was instead of closing the door to separate Angel from the other 4, I placed an old door screen across the opening to her room. This allowed her to feel safe but she was able to watch the movement in the house and the others were able to look in on her too. It also got them all used to each other's scents. Beginning the 1st day, I would go in and read or sit quietly in her room so she could get used to me. The first day she wanted nothing to do with me. She discovered the closet and some blankets on a low shelf where the other cats like to sleep, and claimed it as her own. The 2nd day she came out of the closet for a short time and wanted to be petted, then without warning she hissed and went back into the closet where she sat and studied me.
But from the 3rd day on, she has been very affectionate and wanted attention constantly. Then around the 4th day, I let one cat at a time go into Angel's room for a short time while I was in there. Even though there was some hissing, Angel had her perch in the closet she could retreat to where she felt safe, yet could observe the others and see they meant her no harm. On the 5th day, I let the dogs outside, and confined the other cats in our bedroom, and brought Angel out to let her look around. When she was ready to return to her room, I then let the others back out. On the 6th day, I took the barrier down as I felt confident there wouldn't be any fights by this time. One by one the others would enter her room and look around, and then leave. That afternoon I once again confined the others and she ventured out and explored all over the house including the basement. Then first thing in the morning on her 7th day with us, I was feeding the rest of the animals and she came walking into the kitchen to join the group on her own and ate beside Gidget, the older and calmer of my two cats.
Although Angel still gets spooked if there's too much commotion around her and runs back to her "safe room," she is making wonderful progress every day. What a difference a week has made - Angel has gone from a scared and timid girl who didn't want me anywhere near her, to becoming a very affectionate lap cat. My cats are all females and non-confrontational, and I think that helped make everything go much easier. However, if your cats tend to be aggressive or are males, you may want to move more slowly.