Adopting A Loving Pet
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Adding Another Cat To Your Household

Introduction | Step One: Prepare An Isolation Area | Step Two: Getting The New Cat Settled In | Step Three: Gradual Association By Scent | Step Four: Allowing Visual Contact | Step Five: The Meeting | Other Tips


When a new cat meets your resident cat, the two need time to get used to one another. Careful planning is essential to a successful introduction of a new cat into your home. Take it slowly. A pattern of fear and aggression can be established in one or two encounters, and is much harder to break than to avoid. A certain amount of hissing and posturing is to be expected, but don't risk an all-out fight. When in doubt, wait a few more days before proceeding to the next step.

Ideally, the New Cat would be younger and smaller than the Resident Cat, and would be a sexually immature or spayed/neutered member of the opposite sex. The more the introduction deviates from the ideal, the more difficult it may be. This does not mean it is impossible, only that it may take longer. Avoid bringing a rambunctious kitten into a home with cats older than eight years; think carefully about any age difference greater than five years. Also note that strays and hand-raised kittens often have a more difficult time adjusting to others.

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Step One: Preparing An Isolation Area

Any new cat, but particularly a rescued stray or one from a shelter, must be physically isolated from your Resident Cat for 10 to 14 days to make sure he is not incubating a contagious disease. He must be thoroughly examined by a veterinarian for parasites and disease and tested for FeLV (feline leukemia, which is contagious between cats) and FIV (the feline equivalent of AIDS, contagious between cats) before it will be safe for him to come into contact with the Resident Cat. It also is not unusual for stray or shelter cats to have URIs (upper respiratory infections or "kitty colds"); it is better to avoid exposing your Resident Cat.

Here are the steps involved in setting up an isolation area:

  • Set up the area in advance, to minimize disruption to the Resident Cat upon arrival of the New Cat. It should be a room with a door that can be closed to ensure that there is absolutely no contact between the New Cat and the Resident Cat. A spare bedroom is ideal; a bathroom is fine.

  • If the Resident Cat usually sleeps with you, do not use your bedroom as the isolation area.

  • If the bathroom will be the isolation area and the Resident Cat's litter box is currently located there, move the box to a new spot. If possible, do this at least two weeks before bringing the New Cat home, moving the box gradually.

  • The isolation area should be cat-proofed for safety and include food and water, toys, a litter box placed as far as possible from the feeding dishes, and a cave-like hiding box lined with something comfortable – preferably an unlaundered item of clothing you have worn (a T-shirt, etc.).

    • With cats or kittens that have lived outside and have no prior litterbox experience, using freshly scooped, but slightly used, litter helps that transition. It is also best to avoid using any latex-, foam-, or rubber-backed rugs in this area until sound litter habits have been established.
The worst mistake is to bring the new cat in and put him down on the floor in front of the existing cat, and to expect them to "make friends" or "work it out."

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Step Two: Getting The New Cat Settled In

  • If possible, have a stranger or non-family member bring the New Cat into the house. In any case, the New Cat must be in a carrier.

  • Take the New Cat directly into the isolation area; do not stop to greet the Resident Cat. Open the carrier door and leave the room immediately.

  • Wash your hands. Spend at least an hour with the Resident Cat. Do not go back and check on the New Cat. He needs some alone time to settle in. Studies have shown that cats respond to environmental challenges before they respond to social invitations.

  • Several hours later, slip into the isolation room with a small portion of food, preferably when the Resident Cat is not watching you and/or when another member of the household is playing with her. Sit quietly and talk softly. Wait for the New Cat to come to you. When he does, let him sniff you. Slowly, extend a hand. Do not try to pick him up. Remain for 30 to 45 minutes and leave with just a cheerful "see you later." Wash your hands if you've been petting the New Cat. Visit him several times a day, one hour at a time.

    • The New Cat may hide under the bed, in the carrier, or otherwise appear fearful for several days. If so, continue visiting, but do not force contact. To encourage him to bond with you, let him associate you with something good. Do not leave food in the room, but bring some each visit. He may wait until after you leave to eat it. Do not proceed with the next step until the cat is comfortable with you, and is eating, drinking, and using the litter box. Remember that you are not being cruel to this cat – you are allowing him time to adjust to his environment. (If you adopted a shelter cat, consider his alternative.)

  • Continue with your normal routine. The Resident Cat may hiss or growl at you because you smell like an unknown cat. Note how much time the Resident Cat spends sniffing around and sitting outside the isolation room's door. Do not proceed to Step Three until all hostile responses to the scent and doorway have ceased.
Throughout this process, be sure to spend quality time with the Resident Cat. Talk to her and tell her that although things are not the way they used be, she is still special. Play her favorite games. Groom her daily, if she enjoys that. Give her treats by hand.

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Step Three: Gradual Association By Scent

Cats base much of their identification on scent; if a scent is familiar and associated with something pleasant, it is less likely to be feared. While both cats will be picking up each other's scent indirectly from day one, once the New Cat is comfortable in the isolation area, you can increase scent-recognition prior to visual contact.

Note: Unless the New Cat comes from a foster or similar situation, has been vet-checked, and is healthy, do not begin this step prior to the 10-14 day quarantine. Some diseases (e.g., ringworm, FIP) can be transmitted via contact with objects.

  • If each cat sleeps on a blanket, T-shirt, or other cloth item, bring the New Cat's blanket out of the isolation area, and place the Resident Cat's into it. You may also use the carrier for this step.

  • Casually place this article somewhere the Resident Cat will happen upon it. Watch carefully. The Resident Cat's response to the scent of the New Cat can be telling. Some cats will posture, hiss and even attack the item (difficulty ahead) while others will stalk and growl, run off and then return again and again (typical). Still others will approach the item curiously and sniff it with great excitement (prognosis: good). Leave the item out until the Resident Cat loses interest in it.

  • Repeat this process, but put the New Cat's blanket next to the Resident Cat's food bowl, and vice versa. This will associate something pleasant – food – with the scent of the other cat.

  • Move both cats' food bowls closer to the door of the isolation room – again, create a pleasant association (food) with the scent of other cat.

  • Confine the Resident Cat and allow the New Cat to walk around in the house – this gives him a chance to become accustomed to the larger environment, and will leave his scent behind. (You may want to allow access only to parts of the house, to avoid losing the cat in a closet.)

  • Confine the New Cat in another room for about an hour and allow the Resident Cat to roam and visit the isolation area.

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Step Four: Allowing Visual Contact

Once the Resident Cat is accustomed to the New Cat's limited presence, allow them to see each other without making full contact.

  • Plan A: Stack two tension gates that are at least 36 inches tall in the New Cat's doorway. Rigid plastic mesh baby gates are available at most children's specialty and department stores. If there is reason to believe that either cat will get over the gates, use Plan B. It is very important that the cats not meet and fight.

  • Plan B: Jam the door to the isolation room with two hard-rubber door stops. Place them on opposite sides of the door, and leave it open about two to three inches. Make sure that neither cat can fit his head through the opening. Ensure that the door is secure and will not open further or slam shut if a cat jumps against it. The cats should be able to touch noses and bat at each other with their paws, but not make full contact or bite. Keep the door closed when you are not at home or cannot at least peripherally supervise.

  • Continue to feed the cats near the open door. Move the food bowls back a few feet if necessary.
Do not proceed to the final step until the cats seem relatively calm in each other's presence. Hissing, posturing and growling should be at a bare minimum.

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Step Five: The Meeting

The first introduction may last five minutes or an hour, depending upon the level of tension. If either cat is overly fearful or aggressive, separate them and try again at another time. Don't give up too quickly, but remember that the primary goal at this point is to avoid a fight.

  • While the Resident Cat is occupied elsewhere, take down the gate or open the door to the New Cat's room. Let the New Cat emerge at his own pace. Allow the cats to happen upon each other. Don't interfere, but do not leave them unsupervised. Have your "distraction devices" handy (see below).

  • The Resident Cat may start to stalk and chase the New Cat; the New Cat may do the same if the Resident Cat enters the isolation area. There may be hissing, growling, or posturing. If so, try to distract the cat who is more upset or aggressive by throwing a toy across his field of vision. The second the cat stops that behavior, praise him. If the hissing resumes, distract him again, and praise.

  • If a fight does occur, keep your hands away. Do not attempt to handle either cat. Bang a pot with a spoon or throw a large book to the floor. These loud noises won't be associated with you, but will distract the cats and send the message that hostility generates an unpleasant noise. A second choice is to shout or clap your hands, but you don’t want to make either cat afraid of you.

    • Cat fights usually sound worse than they are. Cats yowl, but if their nails have been trimmed, damage should be minimal. Some declawed cats may bite. When things have cooled down considerably, go over each of the cats' bodies carefully and check for wounds. Bites and punctures wounds may not be visible, but can become infected and abscess; continue to check for two weeks after any fight.
Unless there is obvious damage needing immediate attention, be sure to wait to examine until the cat is completely calm – pupils not dilated, tail not twitching, ears in a relaxed position. An upset cat may reflexively bite anyone or anything that comes near.

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Other Tips

General rule of cat behavior: A cat is not a dog; its goal in life is not to please you. Yelling at or punishing a cat will not change its behavior, but may make the cat afraid of you. Never hit a cat or treat it roughly. To get a cat to stop doing something, give it something else to do that it likes better. To convince a cat to do or accept something new, associate it with something familiar that the cat likes (food or a toy, for example).

The introduction of the New Cat can take anywhere from several days (kitten/kitten or juvenile) to several months (adult stray/adult prima dona). Watch for signs of stress. Eating food quickly and then vomiting; or excessive grooming, sleeping and/or drinking are all signs that a cat is not happy. Spraying, mewling, hiding and indiscriminate urination and/or defecation also are associated with anxiety and stress.

  • Use play to increase a nervous cat's confidence. A "fishing pole" toy is great for this. Drag the object along with small, erratic movements, the way a mouse might move. Be sure to allow the cat to "catch the prey." During the fifth step, parallel play (two toys) is a great way to help the cats become accustomed to each other, providing a positive association as well as distracting their full attention from the other.

  • Do not promote competition. Maintain two separate litter boxes, in different areas, until the cats are completely at peace. Either Resident Cats or New Cats may block doorways and deny access to a litter box. Don't be in a hurry to consolidate. If a cat can't get to his box, he will be left with no choice but to create a new toilet area. (Note the rule of thumb of one litterbox per cat.)
Eventually, hostilities will decline. The two will coexist peacefully. They may even start to groom each other and share sleeping spots. Best wishes to you, your resident cat(s), and your new friend.

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Sources of information for this article include: