Cats are very territorial by nature. They do not like outside disturbances in their households, so bringing home a new cat can be traumatic for both your established cat and the new cat! By following the guidelines below, you can make the transition much easier and hopefully have a happy household with two or more compatible cats. Remember to let cats decide when it is time to move on to the next step and they will do that by acting normally i.e. no hissing, growling, spitting. Both cats should be acting calmly. To introduce any new animal into your household takes a lot of time and patience. Don't expect things to be perfect overnight or try to rush things. You may end up with arch enemies instead of best friends.
PUT YOUR NEW CAT INTO A SMALL ROOM FOR THE FIRST 7 TO 14 DAYS. This is to be your new cat's "playpen" and safety area. Put litter box, bed, food, water, scratching post and plenty of toys in his room. Provide your existing cat with his litter box, bed, toys, etc. Allow your existing cat to sniff at the door. He may spit and growl a bit, but that's OK. Let him.
PAY LOTS OF ATTENTION TO YOUR EXISTING CAT. This will help your existing cat feel more secure and not think that someone else isn't going to take your affections away!
USE SCENTED FEEDING DISHES. Next, take a small wash cloth, rub it on your new cat and then place it under the established cat's food dish just before feeding time. Do the same for your new cat, placing a scented cloth form the existing cat under its food dish. Repeat this procedure at each feeding (always reviving the scent by rubbing the cloth on the opposite cat) until each cat eats calmly with no hesitation and no hissing or growling. DO NOT CONTINUE ON UNTIL EACH CAT IS ACTING NORMALLY! This step may take up to two weeks to complete.
NOW USE CLOSE SCENTED FEEDINGS. Place each cat's food dish on respective sides of the door where your new cat is kept. Feed each cat on each side of the door, still using the scented towels under the dishes, until there is no hesitation to eat and no hissing or growling. DO NOT CONTINUE ON UNTIL EACH CAT IS ACTING NORMALLY! Do not try and rush it. This step may take up to two weeks to complete.
ALLOW LIMITED CONTACT FOR 5 TO 10 DAYS. Now is the time to let the cats start seeing each other without full body contact. Stack two 36" high tension gates in the newcomer's doorway. Rigid plastic mesh baby gates are available at most department stores. Many pet stores carry them as well for just this purpose. If you have reason to believe that either cat will get over the gate set up, then use Plan B. Plan B: Jam the door of the isolation room with two hard rubber door stops, one on each side, with the door cracked open two to three inches. Make sure that neither cat can fit his head through the door. Check that the door is secure and will not suddenly pop open or slam shut if one of the cats hit the door aggressively. They will be able to touch noses, whack each other with their paws and investigate without full body contact.
CONTINUE THE FEEDING RITUAL DESCRIBED IN NUMBER FOUR ABOVE, with each cat on their side of the baby gates. You may eliminate the scented towel under the food dish at this time. When you are not home or able to supervise peripherally, close the door. DO NOT PROCEED to step six, even after ten days, if the cats do not seem relatively calm in each other's presence. Hissing, posturing and growling should be at a bare minimum before proceeding to step six.
PLAY THE SWITCH GAME FOR 3 TO 10 DAYS. After going through the scented feeding dishes and limited contact exercises above, put your old cat in a room and let your new cat out to explore for about 12 hours. Make sure the new cat has access to his room. Then switch by confining your new cat and letting the established cat back out to explore. Continue this switching cycle for three to ten days.
LET THE KITTIES WORK IT OUT. After the switch game leave the door open to your new cat's room and allow the two to meet. DO NOT PUT THEM FACE TO FACE. Allow them to find each other. There may be hissing, growling and hiding. That is okay. Let the hider hide. It can sometimes take two or more months for the two to become friends and it is a good idea to keep the cats separated during this time if you feel that one cat may bully the other.
ALWAYS PROVIDE A SECOND LITTER BOX, SCRATCHING POST, FOOD AND WATER BOWLS IN A TOTALLY SEPARATE LOCATION FROM EACH OTHER. Since cats are territorial, you need to provide seconds of these important items so all the felines are happy and willing to use them without fear that the other cat will bully them.
DO NOT LET ONE CAT BECOME A BULLY. If one cat always seems to bully the other, be ready with a squirt bottle (set it on straight stream) to break up any cat fights. Just make sure it is harassment and not play! Do not leave the cats alone together unsupervised if you are having a bully problem. Separate them when you leave.