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Introducing Your New Cat to a Resident Cat

Integrating a new animal into your home requires time, effort, and patience!  You may experience some frustrations.  Every animal needs time to adjust to its new surroundings.  This is especially true when bringing a dog or cat into a home which is already inhabited by other pets.

Personal space for each cat

Before the newcomer arrives, be sure to invest in a second set of feeding dishes and a second or third litter box.  The existing cat may not be willing to share these personal items with the other cat resulting in more trouble.  It’s bad enough, after all, for your pet to realize that he is no longer the only king of your jungle:  sharing his food and his toilet with your new “baby” is adding insult to injury.  Prior to arriving with the new cat, set up an area that is isolated from your existing cat.  A spare room or bathroom may work well, but be sure you do not pick one of the residing cat’s favorite places.

An easy-does-it introduction

If you want to avoid great trauma, hostility, and possible cat fighting, make the introduction between the two felines as gradual and comfortable as possible. 

  • Bring the new cat into the house in a carrier and go straight to the isolation area.  You can let the new cat explore the new space and get used to the new odors. 
  •  Give the residing cat its first taste of existing in a multiple cat home:  take the carrier back out to the other part of the house and leave it down for your cat to happen upon.  You may be surprised by how much just the odor of the new cat will upset the existing cat.  Typically, you will have to endure some spitting, hissing, and growling during this entire process.  Leave the carrier out for some time until it is causing a minimal reaction.  It is best not to try to comfort the cat until he has calmed himself down. 
  • Next, you should spend quite a bit of quality time with him, reassuring him that he is still very important to you.  It may be uncertain whether cats feel jealousy, but it can certainly seem that way given how the existing pet will behave if the newcomer gets too much attention.  Be sure to always put the resident cat first, feed her first, talk to her and pet her first, and just spoil her in general.  If good things happen to the residing cat in association with the presence of the new cat it will help in assuring the second cat’s acceptance. 
  • To increase subtle exposure and counter condition the cats, try feeding the present cat(s) and the newcomer near either side of the isolation room’s door.  Don’t put the food so close to the door that the cats are too upset by each other to eat, but rather slowly move the dishes closer to the door as the cats appear to become more comfortable with one another’s scents and sounds.  This eating regime will help start things out right by associating something enjoyable (eating) with each other’s presence.  You can also encourage this by sharing each other’s scent with something positive – interaction with you.  After spending time stroking and cuddling the new cat, go out and play a favorite game or stroke and cuddle with your existing cat – and vice versa.  If you get any negative reaction from either cat, go and change clothes and wash your hands thoroughly.

Limited interaction

Once the two-week isolation period is over you can begin to let the cats have more exposure to each other, but never advance to the next step until the residing cat seems ready.  The door of the isolation area can either be blocked off using multiple plastic mesh baby gates or by wedging the door with two doorstops in a slightly open position.  The goal is to allow the cats to see one another but not be able to physically touch.  This will help prevent injuries.  Also, allow them to see and smell each other only when you are present.  You can also put a long strip of fleece under the door and encourage the cats to play with it.  Once this situation seems to be no big deal you can try letting the new cat out.  But only take this brave first step when the residing cat is busy elsewhere in the house.  Let the cats find each other and be prepared for a little friction.

Get ready to referee

When the two cats finally sniff each other out, you should have on hand a couple of towels or pillows, a squirt gun full of water, or something with which to make a loud noise.  Don’t be surprised if round one ensues.  If it does, DO NOT try to physically separate the two cats.  Loud noises, soft flying objects, or a stream of water are more than sufficient to stop a scuffle.  Luckily, most encounters will sound much worse than they are, and the damage that the cats inflict upon one another should not be serious if you are present to break it up in time.  For that reason, you should only let the new cat out into the rest of the house when you are home.

Peace at last

Once the cats seem entirely comfortable with each other, you can leave them alone together all the time.  Hopefully, you will be one of the lucky cat owners who end up having cats that get along so well that they groom each other and sleep together.

As long as all parties seem happy and healthy, you have done your job of making the transition as easy as possible.


If you would like to work with a Wisconsin Humane Society behaviorist one-on-one regarding this behavior topic, please call 414-431-6173 or email behavior@wihumane.org to schedule a consultation.

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