Upon bringing your new cat home, immediately put your pet into a private room where he or she will begin to settle in for her their week. Your resident cat should not be allowed to enter this room or to stay at the door growling and hissing. After one week has passed, allow your resident cat to explore the door of the room where your new cat is residing. After all signs of aggression (hissing or growling) have subsided, open the door a crack. Use a doorstop or hook to secure the door. Again, wait for the hissing and growling to disappear.
If you have a large carrier or crate, place your new cat in it. Bring the cat into your main living area. Try to feed both cats treats or food at the same time, so they associate each other with pleasurable experiences. When the cats are comfortable in this situation, let them interact through the barrier. If there are any signs of aggression, you may want to start out with introductions for only short periods of time (five to ten minutes) or go back to the separation phase. Gradually increase the time the cats spend together as long as they are not aggressive to each other.
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