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Integrating Kittens with Cats

Introducing Young Kittens to Adult Cats

by Margaret Schill

Adult cat hissing at kitten. Kittens can be a threat to adult cats. This adult cat was fine with the kitten after many days.

Cats are territorial, some more than others, and in most cases, do not initially take well to “intruders” in their territory, not even to small kittens. By doing a slow integration procedure, with gradual amounts of exposure over a whole lot of days or even weeks, building up to full-time mingling, things will usually work out fine.

A kitten under 16 weeks old is a baby, physically weak, and can easily be hurt by an older cat. So, your primary concern is for protecting the kitten. Do not rush the introduction process. Once things go badly, they often stay bad. Your goal is to try to not have negative things happens between the new kitten and the older cat (except a bit of hissing).

There are some adult cats who take to little kittens right away, happily filling in as "mom". This is not typical, though, especially for adult cats who never had any dealings with little kittens. Most adult cats don't act like mother substitutes to kittens. That does not mean they won't come to accept a kitten living in the same home. Adult cats and kittens can and do certainly wind up getting along, as the kitten and adult cat in the picture above finally did. But it is not usually the easy, quick acceptance that some people think it will be with many adult cats, where you just plop a little kitten down with the adult cat and have everything be fine. It almost always won't be if you do that. Since starting out badly will set the tone for the relationship, and it is only kind to do all we can to reduce stress and fear in our cats, proceeding slowly with introductions is always the best thing to do.

See below for the integration steps and procedures

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Big cats scared of tiny kittens

A tiny kitten is a threat to many adult cats, (but not all adult cats), as in nature, it would still be with its mother for up to about 6 months old, under her care and protection. The older cats may be wary that the mother will come around looking for her kitten, and that would mean trouble for them if caught near the kitten. It will take some time for the big cats to realize no angry mama cat is going to be coming around. Until then, many adult cats will hiss at the kitten, and even swat at it, trying to keep it from them.

Even if an appearance by an angry mother cat is not a concern of theirs, adult cats still will often try to make an “intruder” leave. Or, the adult cat will try to leave, by avoiding all areas the kitten is or may be in. Some adult cats get very distressed and frightened by little kittens to a greater degree than they do new adult cats, as odd as that may seem. For adult cats who never saw kittens before as adult cats, kittens are strange creatures, not acting like proper cats in the viewpoint of the adult cat who never saw little kittens before. Little kittens make different noises, and move differently than adult cats. They often are overly bold, just trotting right up to an adult cat, not knowing the proper adult cat conventions of dealing with a sudden stranger cat. Many adult cats don't know what to make of tiny kittens and this can worry and stress them. Most creatures fear what they don't understand.

Adult cats who had previous experience with little kittens won't feel as above and will be more likely to accept another new kitten more readily. For them it's "been there, done that". Adult cats who never lived with any other cat will usually have a more difficult time accepting any new cat, be it another adult or a little kitten.

Some adult cats actually accept other adult cats better than they do tiny kittens, depending upon the personalities of the two adult cats concerned. A timid, non-energetic adult cat is going to have a happier, less stressful time getting used to and accepting another adult cat with that similar temperament, than with a wild and crazy little kitten who takes to jumping on sleeping adult cats in attempts to play, not yet having learned "kitty manners".

Kittens not good playmates for Adult Cats

If one is thinking of getting a young kitten as a companion for an adult cat, think again. It is kinder to pair cats in the same life stage since their needs, desires, sizes, energy levels and interests would be more aligned, and they would therefore more likely become buddies. Sometimes one doesn't get a little kitten intentionally, such as finding an abandoned kitten. However, one does need to then realize the adult cats most often are not going to be happy about it, and realize that a tiny kitten is not a suitable as an intended companion or playmate for an adult cat at the time the kitten is still so tiny. The extreme size and strength difference alone clearly points that out in terms of ideas of playmates. An adult cat is HUGE compared to a tiny kitten so no way can they play wrestle together to the satisfaction of each of them. And little kittens love to play wrestle.

If one has an adult cat and wants a little kitten, it is best to get two little kittens then. That way the two kittens can play with each other in the way little kittens do, and the adult cat won't get harassed constantly by a little kitten desperate for some play. Little kittens want to play all the time, and adult cats do not. Otherwise, with just one little kitten and an adult cat, you wind up with a frustrated little kitten and a frustrated adult cat.

Read more about why it is best to get two kittens and more about why a single kitten is not good match to plan on serving as a playmate for an adult cat:

Paws Chicago ( "Longer-term, it is almost certain that the two will never have a close, bonded relationship, even after the kitten matures, since their experiences with one another from the beginning of the relationship are likely to be negative. An older cat is better matched with someone of his or her own age, who has a similar temperament."

Independent Cat Society ( "Kittens who remain with a littermate or a similarly-aged companion are healthier, happier and better socialized."

"A kitten may have too much energy for an older cat. Kittens want to play and run constantly and require a lot of interaction. This may overwhelm and irritate an older cat .... This makes two very unhappy cats ..."

Nanaimo grooms orphan kitten
This kitten and adult male cat are fine for "parent/child" relationship, but not as playmates. Photo courtesy of Alicia.

That said, at times one will take in a tiny kitten, while having an adult cat or cats. Things can wind up fine with considering the above, with not expecting the tiny kitten to be a playmate for the much larger adult while the kitten is still so tiny, and by following the integration steps below. If one understands the different behaviors, physical abilities and needs of each life stage of cats, handles things accordingly, not getting upset if the older cat doesn't want to play wrestle with or sleep cuddled with the kitten, things will work out a lot better.

Here is a link to a successful integration story starting with a 12 week old kitten and five adult cats- It did take some time, though, and each of the adult cats took differing amounts of time to accept the kitten. In that situation, the three adult males accepted the kitten weeks sooner than the two adult females.

Steps for introducing little kittens to adult cats

1) Isolation: Isolate the new cat completely for a few days. 2) Scent Familiarization: Scent familiarization with items, such as towels rubbed on each cat, then left in the area of the other cat. 3) Room Swapping: Switching the cats' places for a while every day, with no physical contact between them to allow even more scent familiarization. 4) Visual Familiarization: Seeing each other with no physical contact, such as from a slightly cracked opened door or with one of the cats in a carrier or cage for a few minutes only. 5) Developing Positive Associations: Start developing positive associations with no physical contact, such as by feeding the cats on opposite sides of a door when cracked opened and even when it is shut. 6) Short Supervised Visits: Brief, highly supervised visits paired with food or treats. 7) Separation at Signs of Hostilities: Separate the cats at signs of hostilities, or great fear. Learn cat body language to tell when a problem is starting. 8) Longer, Carefully Supervised Visits: Mingling under very careful supervision for up to a few hours, before total separation again. Adjust the length of time depending upon whether there are any signs of hostilities or stress, but no matter how well things seem, do not yet permit 24/7 free mingling. 9) Limited Free Mingling: Supervised free mingling except when the people are not home or asleep, so quick intervention can be done if needed. 10) Free Mingling Full Time: The cats are let together freely all the time when all the above steps have gone well, and when the kitten is 16 weeks old or older. No full-time mingling for infant kittens for their safety. Backtrack to the limited mingling if the cats weren't quite ready to be together all the time.

You may come across advice saying to ignore the new kitten in front of the resident cat, so the resident cat doesn't get upset. Do NOT do that. If you ignore a new cat, it makes the resident cat feel you don't really care or want that cat there either. It also makes the new cat feel unwanted and uncared for. That is not any way to treat a new kitten, whose whole life was turned upside down. It is good to show affection to the new cat, so the resident cat sees you want that cat in the home. But, you don't go overboard with shows of affection to the new cat in front of the resident cat.


New kittens in isolation, with all the comforts they need. Good thing they were isolated at first, since these kittens had fleas and roundworms.

Before any mingling of the new kitten is allowed with other cats, a vet check is needed, so the new kitten needs to remain totally isolated from other cats until a vet appointment can be made. This is very important! The new kitten should be set up in his/her own room with no access at all to other cats or any sharing of litter boxes, food and water bowls. Even if the kitten had been vet checked prior to entering the home, the kitten could have developed an upper respiratory infection that had not shown symptoms yet that would be spread if the kitten sneezed near another cat, or may have some other illness or parasite that was not observed or diagnosed by the vet. So the kitten should be isolated from other cats for at least 5 days, even if the kitten had a vet check before entering your home. The days spent isolated from other cats allows you to note any signs of illness or parasites.

Another important reason for the initial isolation from other cats (not from the humans!) is that the kitten’s whole world has been turned upside down, and s/he needs some time to get his bearings and begin to relax about his/her new life situation. S/he not only has to get used to a new place, but new people as well. Not good to overwhelm and stress him/her with all three things when s/he first arrives at his new home. The kitten will be upset about losing his/her mother and siblings too, if very young, so will often not be in a good mental state at first to take on meeting a new cat. (Kittens should stay with their mothers for 12 weeks, but sometimes one winds up with a kitten parted from the mother too soon.)

If a bedroom will be used as the kitten’s “safe room”, put some things under the bed to block the middle, but leaving some room for the kitten to feel she is hiding, so that you will be able to reach the kitten if necessary or desired when s/he hides under the bed. Do provide “hidey” places for the kitten when s/he feels nervous or scared, but not any that you are unable to reach the kitten. A cardboard box set up like a "cave" will work. A kitten proofed bathroom can be used for a safe room for the first few days, and is especially good for kittens rescued from the streets who may have fleas, until the flea situation is dealt with. Fleas will lay eggs in carpets, so rooms with them aren't the best choice at first.

For these five days, or more as necessary, of the kitten isolated from other cat, take the time for you and your new kitten to get to know and bond with one another. When the kitten feels safe with you, meeting new cats will be easier for him, as he will know he has a new “mother” to comfort him when he is scared or stressed. This will also help with his grief of losing his mother, which he will feel keenly. It would be good if the kitten can stay in the same room as you sleep in, so you can comfort him should he cry during the night.

Scent Familiarization

Next, after the all-clear from the vet and any parasite situation has been dealt with, still keep the cats totally separated, but do swap scents between both cats by rubbing a towel on each one, then placing the towel in the area of the other so they can smell the scents of the other without the stress of the other being present. Also, you can use another towel to rub one cat, rub it on the other, and then back onto the first cat to mingle their scents on their bodies. Refresh the scents periodically. Do not rub artificial substances on the cats, such as perfume, vanilla or baby powder. For one thing, the cats will lick off anything put on them, and some things are toxic and/or taste terrible. For another, that won't make the cats smell the same and then like each other. Once they wash themselves, they will smell like they naturally do. You want them to get used to each other's own natural smell.

Smell is very important to cats, so you want each cat to have lots of experience smelling the scents of the other, even before meeting, as a way to get familiar with each other and considering the smell of the other as “belonging”, “normal”, “ok”. Use your hands as well to swap and mingle the scents. After having cuddled the kitten against you, leave the shirt you wore on the floor in an area the big cat can spend time smelling it. Your scent mixed with the kitten’s scent is good for your older cat to smell, as it associates something good (you) with the new thing (kitten smell).

Hold off on the other steps until the scent swapping has been done a day or two at least. Observe how the adult cat reacts to the towel or blanket that has the kitten's scent on it. If the adult cat hisses, growls at or urinates on it, stay on this step until the adult cat can merely sniff the kitten-scented towel or blanket without any upset reactions.

Room Swapping

This is a more intense form of scent familiarization. While the kitten is safely contained in a carrier, so there is no chance of any physical contact, and taken out of the Safe Room, let the resident cat explore the kitten’s Safe Room, to get to smell the kitten smells up close, without the “threat” of the kitten actually being there. When the resident cat is in the kitten’s room, shut it in, and let the kitten safely explore the rest of the house or one other room, under your close supervision. Kittens can squeeze into places you might not expect, such as up inside furniture and appliances, so watch very carefully. You will have “baby proofed” your home first, getting down on your hands and knees to see what and where a kitten might see that could be a danger.

Room swapping also allows each cat to set down their scent, since cats have scent glands in their paw pads. With every step, a cat leaves a scent "foot print". This then makes the scent of the other start to be a natural part of the territory when the cats get switched back to their respective areas.

Be sure to not do this step until the kitten has been to a vet and is deemed free of diseases and intestinal parasites. Some diseases and parasites can be spread from cats sharing litter boxes, food and water bowls and the cats may use the litter box of the other or eat and drink while their places have been swapped.

Room swapping can be done along with Visual Familiarization, described on the next page of this article.

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Why have more than one cat?

While it is true that cats are territorial animals and can do fine as an only cat, it really is better for many cats to not be the only cat.

In nature, cats are not the total loners it is sometimes thought they are. They do have friendly social interactions with certain other cats.

Indoor only cats do get bored and lonely in homes where the humans are gone for many hours a day. A companion cat can help relieve those feelings in a cat- provided they get along!

The younger the cat is, the more important it is for there to be another cat, preferably one near the same age. Cats under a year old especially benefit from having a companion cat. Not only do young cats like to play with other cats, but they learn social skills and comfort one another.

Of course, one needs to introduce cats slowly, as per the guidelines in the article on this page, for the best outcome. If both cats are under a year old, the free mingling point is usually reached sooner than when the cats are older.

Try to avoid pairing kittens with older cats. Older cats do NOT want to play all the time like kittens do, and you will more likely wind up with a frustrated kitten and an irritated, stressed older cat.

Litter box Needs

A new cat needs a new litter box. See a wide selection of litter boxes by clicking here.

Click here to read about litter box guidelines especially for homes with more than one cat. The general "rule" is one more box than the number of cats.

Keep in mind that a small, young kitten will need a litter box with lower sides than older kittens and adult cats. The small sized plastic litter pans have low enough sides. Even though kittens will outgrow the small sized pans, they don't cost much more than US$3.00.

Also realize that when very young kittens need to use the litter box, they need it NOW! So be sure a very young kitten is never too far from a low sided litter box. That can be arranged by not letting very young kittens have free run of the entire home. Very young kittens should not have free run of the home anyway, for their safety. Tiny kittens can squeeze under and behind places, such as appliances, you did not think they could, and sometimes they get stuck, or hurt on things.

Cat age comparisons

An 8 week old kitten is comparable to a 10 month old human (not counting that an 8 week old kitten can already walk, run and jump).

A 1 year-old cat is comparable to a 16 year-old human. A two year-old cat is comparable to a 25 year old human. A 5 year-old cat is comparable to a 38 year-old human. (age comparison from

When one considers this, one can hopefully realize that a kitten just is not a match as an intended companion and playmate right away to an adult cat in terms of life stage, not just considering disparate size and strength.

Kittens Need Kitten Food

Kitten food provides the extra calories and nutrients fast growing kittens need. Kittens should be fed kitten food until they are 6-9 months old, unless the kitten is a large breed such as Maine Coon or Ragdoll. Large breed kittens should continue on kitten food until they are a year old.

Before you select a brand of cat food, please read the following articles for some important information:

"What you Need to Know About Your Pet's Food"

"Selecting a Commercial Pet Food"

For a general selection of various brands of kitten food Click Here .

For a selection of only natural kitten food,
Click Here.