How to incorporate a new cat, or kitten, into a household with cats

I have been a cat owner (or cat pet if you like) for some years now and I have found that there are only a few ideas that actually help incorporate a new cat into a home of other cats.  The problems of incorporating a new cat into a house with cats is that the cats already present see the house as their territory and cats have a natural instinct to protect their territory at all costs.  This is not something you can break them of because it is an instinct not a behavior.  Sadly, punishing the pet can cause the pet to develop unusual behaviors in retaliation.  Such behaviors can be as simple as urinating on your kitchen rug or as complicated as refusing to eat and hiding in a closet for the remainder of their lives.  By slowly and carefully introducing the new animal into the household it makes for a much quieter and easier introduction for all animals concerned. 

I will caution you, however, that every animal, just like humans, is different and something that works for one doesn’t always work for another, however the steps below, when done in sequence have always worked for me, because they allow the scents of the animals to mingle over and over again until the animals are comfortable with the scent of each other.

• Keep the new animal separated from the others for the first few days to keep them safe.  Allow the others to sniff at the door of the room where they are staying but do not allow them to go in. 
• Pet a regular resident cat and then enter the room and pet the newbie, then go out and pet the regular again.  This puts their smells on each other and gets them used to the scent.  The more you do this, the easier it will be to incorporate the newbie into the household.  (This step is important because animals judge and identify by scent.)  Also, be aware that if there is a person in the home who seems to be the main owner of the animals (ie the one the animals listen to best) then that person should be the one doing this step most often.  

• Give the newbie a blanket or toy that the other animals have used, after a day, take it out and give it back to the other animals (giving the newbie a different one).  This allows the scent of all animals to mingle.
• Use a litter box for the newbie that the others have been using and switch it out with another after about a day.  This allows the newbie to smell the regulars and also gives the regulars a chance to smell the newbie.  Since urine and feces are their way of marking territories, this allows them to mark without it covering your new couch or the bed sheets as well.
• Use a dish that the others have been using for food and/or water to feed your newbie.  Clean it first so that there is no bacteria present, but don’t wash it in extra hot water.  That way the smell of the other animals will linger on the dishes.  After a day, you can switch it out and give the newbie another one.

• After a few days, allow the newbie out to roam a bit while the regulars go in and check out the room.  Be sure to stay with the newbie so that no fights occur.  After an hour or so, put the newbie back so they can rest and relax knowing they are safe.
• Once you begin letting the newbie out, leave them out longer and longer each day.  However, NEVER leave the newbie out while you are out of the house!
• Finally, when you think they have gotten used to each other, let the newbie out for the night and see what happens.  If there are fights, you will need to put the newbie back and try again the following night.

Be prepared for some paw slapping and hissing.  This is a natural thing, but if you follow the steps above, there shouldn’t be much fighting because they will already be used to the smell of each other

• Also, an unfixed female will cause issues as well.  She will go into heat and yowl as she roams through the house and she will also mark with urine because that is how they attract a mate.  Plus the other animals, being fixed, will attack the female when she goes into heat.
• Try not to introduce more than one cat at a time into a household with other cats.  This will cause the newbies to fight each other and the others to attack both.

• Put the animals in the same room and let them duke it out--I found that the more dominant animal will badly injure the less dominant--in many cases it will be your old pet because they haven’t had to fight for what they needed to survive and have lost the edge.

• Tie the new animal on a short leash so the others can smell them--this usually ends up with the other animals taking advantage of the ‘tied’ animal who is limited in his/her movements and usually gets hurt badly because the others are going to fight for their territory and try to force the new animal out of their area.
• Keep the newbie on a porch until the others are used to the newbie being there--I found that this only worked to make the regular residents curious about who is on the porch.  Once the newbie is allowed into the house, the others will viciously attach the newbie who has been tantalizingly close but just out of reach.
• Keep the newbie in a cage in the center of the room where the cats usually sleep--I have found that this not only interrupts the sleeping pattern of the regular residents, but causes them to try to attack the newbie through the cage wires.  If you have a small cage, the newbie has nowhere to go to get away from the sharp claws.  And even a big cage is dangerous with more than one cat because they surround the cage and all of them stick paws inside with claws extended.

• Unfixed females will attack a new female kitten because it will grow up to be a rival.
• Unfixed males will attack most kittens to defend their territory, but will be more likely to attack a male kitten than a female, again because of rivalry.
• Older animals (14 or 15), fixed or unfixed, have a tendency to be either totally neutral with kittens and don’t really care one way or the other, or will be extremely violent towards the kittens not wanting them anywhere around.  You will have to feel them out.  Usually, as long as the kitten stays away from them they will leave the kitten alone.
• Fixed animals are usually more tolerant of kittens than unfixed animals.

• Kittens can’t get into a litter box like older cats can and may have accidents on the floor.  Try to make arrangements for them with a smaller litter box or a litter box with something in front that they can step on to get in.  Make sure they know where the litter box is and how to get into it.  Usually if you put them in the box and let them crawl out they will be fine.  Be prepared, however, because the big cats will use the little one’s litter box because it’s smaller, unused, and they want to put their scent in it.  Quick note here--a cat has a natural instinct to scratch before urination or defecating, so if you have a brand new kitten that doesn’t seem to know what to do with a litter box just keep putting them in it when they begin to scratch.  They will get the idea.
• Kittens can’t eat the big cat’s food so be prepared to feed the kitten in a separate area or the big cats will eat the kitten food and the kitten will go hungry (law of the jungle).
• It is usually very hard to resist that tiny little cry and those tiny little eyes looking up at you, but remember that your other cats will get jealous and will take that jealousy out on the kitten if you are not careful to show them attention as well.

All animals, especially cats in my opinion, are similar to young children in their behavior.  They want what they want immediately. They want to be with their ‘mother’ when they are tired or scared.  They don’t like others to take their ‘mother’s’ attention away from them.  They like their comfort.  They liked to be held and cuddled (well in the case of the cat, petted).