Before you bring your new kitty home, be prepared for hissing, growling, fighting, and territory issues, as your resident cat will most likely not enjoy having her turf invaded by a fellow feline at first. This is normal.
It isn’t unlikely that the Resident Cat may “act out,” and urinate outside the litter box, have a decreased appetite, or over-groom herself. If necessary, consult your veterinarian if she shows these signs.
Make sure and reinforce positive behavior and successful interactions with treats and show each cat plenty of affection.
What follows is a possible outline to make the transition from a one- to two-cat household a peaceful one — just be patient and remember it is a gradual process that may take weeks and even months. Don’t simply put the cats together and “let them work it out” — that’s a guaranteed plan for failure and disaster.
Welcome home: Confine the New Cat (NC) to a room with her own food, water, and litter box (call this her “safe room”). Be prepared to keep her in this space for seven days or more. Visit the NC frequently and show her plenty of affection; also make sure each member of the household (except the Resident Cat) introduce themselves and spend time with her as well. Equally important: show your Resident Cat (RC) regular affection, too, as it’s easy to get swept up in the excitement of a new animal in the home.
Common scents: Rub a damp towel on the NC, then rub the RC, and let each cat sniff it, or exchange their pet beds or blankets with each other. The objective is to get each cat used to the other’s scent. Don’t be surprised if either (or both) cat hiss when they smell the other’s scent. You can also use a brush to collect each cat’s fur so they can smell it.
Trading spaces: Have the two cats switch spaces for an hour each day: confine the RC to the NC’s quarters, and let the NC explore the rest of the residence. Have someone stay with the RC during this time and show her affection.
When NC is confined to her quarters, place RC’s food bowl outside the closed door of NC’s room — just be prepared for some hissing and growling.
Building fences: Take a piece of chicken wire or similar material at least 5 feet high and place it across the doorway of a room with no other exit. Place NC on one side of the barrier and RC on the other side. Put some catnip or treats near the barrier on both sides.
Make sure there are no structures near the fence that either cat can use to jump the barrier. Don’t worry about any hissing or growling – the objective is to let the cats see, smell, and hear, but not touch each other. Try and have a couple of these sessions each day, but limit them to 15 minutes.
You can also give the two cats a limited introduction through a cracked door.
Restrained meeting: One person holds the NC, the other holds the RC, and each stands at least approximately 8 feet away from each other. Do not let the cats go or confront each other directly without restraint.
If the “holding” session goes well, set each cat’s food at least eight feet from the other and let them eat, but do not let the cats approach one another.
Meeting time: If there is a minimum of hissing and growling, and you think the time is right, try an unrestrained face-to-face meeting. Before you let the cats meet, make sure there are plenty of “escape routes” for the both cats. Also have a towel on hand.
Place each cat at opposite corners of a room, or ends of a hallway, and let them go. If the felines start fighting, throw the towel on them to break it up (if you try to separate them yourself, you could get injured). If one cat chases or corners the other, immediately return the NC to her quarters and give both felines a treat and comfort. Even if all goes well, try and limit the encounter to 10 minutes.
If all face-to-face meetings are a complete disaster, return to Week 1, and start the cycle again.
Toys and togetherness: If both cats tolerate each other during their face-to-face encounters (with minimal hissing and growling), use various toys and treats to help bring them together.
Once the two cats are comfortable with each other, you can put their litter boxes side by side along with their food and water. Some recommend gradually moving the NC’s litter box next to the RC’s box a little each day so the transition isn’t so jarring.