7 warning signs when introducing cats

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Introducing your resident cat to a new cat can be a challenging task. As a furparent, you need to know some warning signs when introducing cats.

Cats are very territorial and they sometimes prefer having their solitary space. You might run into some problems when you bring a new kitty to your home without prior preparation.

Your resident cat may not like it when a new cat gets into their territory.

Warning signs when introducing cats

The resident cat may become hostile to the newcomer. They may hiss, growl and rumble and even show aggression towards each other.

It is possible to see cats physically attacking each other in such a situation and this is dangerous and can be life-threatening.

With proper preparation, you can introduce cats flawlessly and reduce the chances of aggression and hostility.

Introducing cats may take a few days, weeks, and even months. If you do it properly, they will get along without much resistance and within a shorter time.

How To Prepare and How to Start the Introduction

Cats are very territorial pets. Your resident cat may not welcome your newly adopted kitty because they feel threatened.

Your resident cat will become defensive and try to push out the newcomer from their territory. Whilst this can be normal, it can sometimes turn out to be ugly if the cats are not handled properly.

1. Prepare for a multi-cat home

Before bringing your newcomer cat to the house, you need to prepare to host them. Create a separate room that will host the new cat alone.

The room should be lockable and easily accessible to all family members. It should further be spacious enough to house all the accessories that your cat will need.

Cats playing at home

You need to get more cat resources for your furry friends. Increase the number and variety of toys, cat treats, cat gears, and other essential accessories. You don’t want a situation where your furry partners fight for limited resources.  

2. Immediately after the adoption

After adopting your new cat or kitten, you need to take them to the vet first. Let your vet diagnose them for all the common cat health problems.

If they’re found to be suffering from any medical condition, they should receive proper care and medication immediately.

If it’s the cat’s time to get vaccinated, let him get the prescribed shots. You should not take an unvaccinated cat to your home.

They may easily get some communicable diseases and pose a danger to your feline family.

3. Bringing your new cat home

Get your cat and place him inside a cozy carrier box. You can place a few toys and cat treats in the box to keep your cat engaged through the journey.

The carrier box holding your cat should be safely secured on your car’s seat with a safety belt.

Once you arrive at home with your newcomer feline, take them to their separate room. Do not allow your resident cat to see the feline visitor yet.

Leave the cat inside the carrier box while open and let them come out at will. At this point, the newcomer is probably a little stressed and anxious to know his new home.

Introducing Kittens to Your Adult Cat

Introducing adult cats may be different from kittens. It is much easier for kittens to get along with adult cats.

Some kitty parents have found it easy to get their resident cats to accept the newcomer kitten. You can expect your kitten and resident cat to get along in less than a week.

Kittens are playful and exciting to have around. They are yet to get their natural territorial instincts which come along as cats get older.

Cats relaxing on a window

Your resident cat will also feel less threatened to see a small newcomer than a mature one. However, you should not assume that your adult cat will accept a new kitten immediately.

Follow the following tips to ensure your feline partners get along together.

1. Know your resident cats’ personalities

Does your cat love kittens? You consider whether your cat can freely welcome kittens to play with them endlessly. If you have an elderly cat, then they may get along quickly.

2. Start training your kitten

The best way to ensure that your newcomer kitten blends with the fur family is by training them. Train them not to scratch the furniture and show them the more convenient scratching post.

Let your newcomer grow up with the same life values as your resident cat and they can easily get along.

3. Get them to play together

Cats love playing, and kittens love it more. One of the best ways to let your newcomer kitten feel at home is to give him a playing companion.

Give the feline partners enough cat toys and let them play together. From tugging games to chewing toys to jumping on cat trees, let your cats enjoy and maximize their fun.

For more in-depth details, make sure you read our ultimate guide on how to introduce cats.

Genius Dog 300 x 600 - Animated

Have a look at the video below from Dr. Kim Chainey where she talks about the 10 things you need to know if you have a new kitten.

If you have a dog, don’t worry! Learn how to introduce your cat to your dog at home with our ultimate guide.

Warning Signs When Introducing Cats

You can minimize the cases of intolerance by your feline pets by carefully looking out for warning signs. Your resident cat will be reacting to the new cat, while the newcomer tries to adjust to the new environment.

The following are some of the warning signs when introducing new cats:

1. Staring at each other

Your feline partners will stare at each other immediately after they spot each other. The resident cat may stare at the newcomer for long because they’re feeling uncomfortable or threatened.

Two cats meeting for the first time

If you notice a prolonged stare, then the cats might be building up aggression which might turn out to be ugly. You can come in and separate the cats to calm them down and prevent any attack.

2. Growling

Cats growl to show their fear, anger, repulsion, and distress when in uncomfortable situations. Both the new cat and the resident or one of the cats may start growling at the first instance of meeting. In most cases, the cat who feels more uncomfortable will growl first.

If your resident cat starts growling on the first meeting, they are just trying to communicate their discomfort of having another feline in the house.

Growling is largely normal and should not cause a major concern. In any case, it shows you that your feline partners are mindful of their peace and would raise an alarm if they’re uncomfortable.

3. Hissing

Growling may not be enough for the cats and they may now move it up a notch. The cats may start hissing at each other when their fear levels rise.

Cats hissing at each other

Hissing is a defensive sound that is produced by cats when they feel victimized or antagonized.

If you notice your cats hissing against each other, you need to come in and separate them. Failure to intervene might make the cats escalate their tension.

4. Ears flat or pushed back

Another warning sign to check out when introducing cats is how they move their ears.

Cats will flatten and push their ears back when they feel nervous, threatened, or anxious. They do this because they feel threatened by the new feline.

Cats flatten their ears and moved them back to protect them from any external attack. At this point, your cats are fearful that the other cats may pounce on them and start fighting.

5. Dilated pupils

Your cat’s pupils might become dilated during the first encounter. This shows that the furry partners are fearful and defensive. They are keeping a close eye on what might happen next.

6. Puffing out their fur

Your feline partners may puff out their fur at the first instance of meeting. This is a defensive move as the cats are trying to bulge out their bodies to appear big. The cat that feels more insecure will puff out more fur than the dominant cat.

7. Chasing and hiding

In cases where the dominant cat is scaring off another cat, then the less dominant cat will run and hide for their safety.

Common places where cats can find safety include under the bed, sofa, and behind the curtains.

Sometimes the hiding cat may refuse to come back because they’re scared of the stronger cat. If this happens, then you need to separate the cats and look out for the hiding cat to show them some love.

How To Get Cats to Get Along

There is no definite time when cats will all get along. Some cats will be friends within a few days, other weeks, and some will take months.

You can however come into play and help your cats get along faster and more peacefully.

1. Increase your Cats’ Resources

If you have a single cat, then you need to prepare your home to host multiple cats. The preparation will entail providing the cats with adequate resources to live happily and in harmony.

Cats should not compete for any resource. This may build up tension and make them fight in some cases.

Automatic cat litter box

Ensure you add an extra cat litter box for your newcomer. Cats are hygienic animals and they may not be willing to share a litter box.

You can get an automatic cat litter box if you have a newcomer kitten to make it more convenient for them.

Cats may similarly not find it easy to share feeding resources. This may make the feline partners hostile to each other while competing for food.

Create another feeding station for your new cat. Feeding points should have cat food bowls, an automatic cat feeder, and cat water fountains.

You need to separate where your newcomer will sleep. They should sleep away from the resident cats’ sleeping area.

Consider getting a tall pet gate to separate the two rooms, where the cats can see each other but they can’t physically reach each other. This can help speed up the introduction phase.

For the start, it is important to have the cats sleep in different cat beds. They can, later on, share their beds when they are used to each other.

Get more interactive cat toys for your feline pets. You should ensure that your furbabies do not clash during their play time because of inadequate cat toys.

2. Allow your resident cat to cool down

Once your feline partners have met and raised their curiosity, you need to allow your resident feline to cool down.

A white and brown cat relaxing

Take them to a separate room and let them cool down from the possible aggression build-up. Do not force your cats to get along with a newcomer immediately. Allow them to become friendly at their own pace.

3. Eating together

If your fur friends do not compete for food, then you can have them take their meals near each other. Have different food bowls for all cats and let them eat in harmony.

Make sure all the cats have a generous food portion to reduce any chances of a conflict.

4. Use a Pheromone Diffuser

A Feliway Diffuser sprays pheromones which helps cats to calm down in stressful situations. These scents also help your cat to respond calmly to changes.

Your newcomer cat will easily adapt to their new home, and the resident cats will easily accept the visitor. You can plug these diffusers in your new cats’ rooms, the living room, and walkways.

5. Reward your cats when they tolerate each other

Have some tasty cat treats and reward your cats when they’re staying calm together. Show them that you are happy when they embrace each other.

6 Signs Cats are Starting to Get along

You can know if your feline pets are getting along by looking at how their behavior changes. Cats who once could not stand each other are now embracing each other.

There is no specific time for cats to get along. Some become friends after a few days while others take months.

1. Sharing a room

If you notice your furry partners spending some time together in a single room, then you can be sure that they have started to embrace each other.

The resident cat is now accepting the newcomer as part of the family. There’s no more hiding and chasing.

You can also observe how the cats are behaving in the room. Are they still very alert or do they feel safe together? This will show you the extent to which they have embraced each other.

2. Eating from the same bowl

Friendly cats have no problem eating from the same bowl. You can notice this even when you have given every cat their bowl but they still eat from one bowl while interchanging.

2 cats sharing the same bowl

3. They great each other

Your furry partners are now raising their tails and meowing when they meet. This is a sign that they are mindful of each other.

Cats sniffing each other

They can go further to rub their heads together and even lick each other for some time. This act is an exchange of love and affection.

4. They groom each other

Friendly cats will groom themselves regularly. A cat will help their partner to clean some areas of the body that are out of reach.

Cats grooming each other

5. Playing together

The tugs and runs are no longer boring. Friendly cats will participate inclusively in their games to get the most excitement. They no longer fight for toys. They can now share some of their toys without much competition.

Cats playing outdoors

They further engage in running, jumping, and chasing battles, especially on their scratching posts.

6. They sleep together

After playing together for some time, your feline partners are now tired and sleeping together on the couch. This is to tell you that they can now share the same space without conflict.

If your kitties are showing the above signs, then they have finally accepted each other. The newcomer has now become part of the family and they feel at home.

Cats hissing at each other

However, you should not assume that the cats no longer need their solo spaces anymore. Sometimes cats may want their alone time in a solitary place to rest and calm down.

You should therefore maintain every cat’s room and hiding area. Let them have all the resources available for them whenever needed.

What To Do If Cats Get Aggressive

Sometimes cats can become aggressive when introduced. At such a point, you need to intervene and prevent a possible physical attack. This is especially common for aggressive cats and those that are too territorial.

Two cats attacking each other

To prevent your cats from fighting, you need to introduce them in the presence of a second person. Both of you should stay alert and watch out if there is a possibility of an attack in the first instance.

If you notice any signs of fighting, you need to immediately back off and take the furry friends to their respective rooms. This is a warning sign that the cats might take much longer to get along.

You can then swap your cats’ scents, which plays a role in making the host cat accept others in their territory.

Get some accessories e.g., towels with your resident’s cat scent, and take them to the new cat’s room. Let the newcomer get the resident cat’s scent.

Do the same for your resident cat, let him get the scent of the newcomer. You can also switch the cat’s beddings.

Let them interact with each other’s scent and smell. As you do this, continue making use of the pheromone spray.

Once you have done this for a few days, you can now reintroduce the cats. This time a bit more careful to prevent any aggression build-up.

Have more than one person do this for you to contain any possible physical attack by the fur babies.

I have written an article on how to deal with an aggressive cat. You can check out that article to find more tips on how to cool down your cat when aggression builds up.

What Not to Do When Introducing Cats

Now that we have looked at some of the things you can do to introduce cats, what about the contrary? There are some things that you should try to avoid whenever you want your resident cat to welcome his newcomer furbaby.

1. Introducing your cats too quickly

Once you have arrived home with the newcomer, do not rush to introduce them yet. Let the new cat stay in their house for some time, even days.

Allow them to get familiar with the new house. If you introduce them quickly, then the new cat might feel intimidated. They’re trying to catch up with a new environment plus a new furry friend.

2. Leaving your cats unsupervised

Your cats should not be in close proximity while unsupervised. Every time you want to bring the cats in close contact, ensure you are there to watch over them. You can then be able to monitor their interactions closely.

Cats attacking each other

The cats will also feel safer in your presence. They would come down and have a reduced chance of building up tension.

3. Forcing your cats to get along

Be patient and allow your furry friends to get along with time. Do not force any of them to immediately accept friendship.

You might cause more damage than good when you do this. Make the process as natural as possible. If your furry partners will naturally get along, then they will maintain the bond for long.

4. Shouting at them

When you shout or punish your furry friend for not accepting a visitor, then he might become aggressive. Shouting at your cats will only increase their stress levels and make them more anxious.

To Conclude

If you observe any warning signs when introducing cats, it is best to separate them immediately. Do not force your resident cat to immediately accept the new furry friend.

Let them take their time to learn and embrace each other at their pace.

Thank you for reading through this article. If you have any questions, please leave a comment down below and I will get back to you.

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20 Responses

  1. I know this takes time and patience to introduce a new cat into the house, my concern is the new cat being stuck in a room and not having the freedom if it takes awhile.
    What is your experience or opinion on introducing a a spayed female kitten (4-5 mths) to a neutered male who is about 3 1/2? We thought we were getting a boy kitten to be his friend but long story it ended up being a girl haha. Taking her home after the holidays, and I have lots of toys for her plus food bowls & things for her that were not used by the current cat! I’ve been doing lots of research on introduction & honestly it’s kind of got me stressed out. Especially now that we are bringing back a female vs male!

    • Hi Chelsea, in terms of your kitten being stuck in a room, it is very important to keep her entertained with toys and playtime. This way she wouldn’t feel stuck in 1 room or get bored! Also during the introduction process it is advised to let the cats swap rooms so she won’t be in one room all the time.

      As for the introduction, don’t stress about it too much as long as you do all the steps the right way things should be fine! I would advise you to check out my other article about this https://fursnpaws.com/how-to-introduce-cats it is more detailed and should give you clarity on how to do things step by step. 🙂

  2. We recently got a new cat that I rescued from my sister in laws. She was always stuck in a room and often no one was home. There was another cat in the house and no issue there.
    There are 3 resident cats in my home. All fixed….a 3 year old male, Orion, and 10 month old brother Jasper and sister Luna. The new female cat, Lucy, is just over 2. We also have a small senior chihuahua named Shorty. When we brought Lucy home she was not fixed. She would hide all the time and there was really no aggression between the cats at all besides maybe a small hiss in passing. Lucy is now fixed and has become super sweet to people but is VERY aggressive with the other cats. She is fine with Shorty. Lucy will chase the other cats while high pitch growling. She sounds like a banshee. This is always unprovoked, whom ever she decides to go after will just be laying there. When she does this I catch her as soon as I can and put her by herself in the spare room. I’m having a hard time here because it’s not a constant thing, as they have all been in a room together and there was no issue. I did somewhat notice that it’s been worse if I’m walking around. She will go right in front of me like she is guarding me or something. The others have not gone after Lucy and they haven’t gone after me.

    • Hello, I believe its worth it to do the introduction process from scratch here and separate Lucy from the others for a while while introducing her again step by step. Are they all usually sharing the same food bowl and litter box? Maybe getting Lucy her own stuff when separating her would help too. Hope this helps!

  3. Hi! Loved your article. My 2 yr old yowls all night if he’s separated from our new “baby”-she’s 2 months old. Generally he’s ok with her, they nap together, he’s not bothered about sharing food, he sometimes licks her. But other times he can be very dominant, to the point his fur stands on end and she squeaks. They were separated for the first week, and now they are together. Otherwise my cat won’t shut up. Will this dominance/aggressiveness pass? I worry for her.

    • Hello Alexandra, really glad you like my article 🙂

      In your case, I would advise you to monitor your cat and see whats making him dominant or territorial. Perhaps you need to start separating their food, bed, litter box… it depends on whats triggering his behavior. Once you find out the trigger and you make a change the issue should be resolved.

  4. Hi there! So I have a pair of bonded kitties who have been inseparable since birth (littermates!) who have recently started fighting. It’s breaking my heart. I am not sure what caused it, but I have had them separated for about 2 weeks now. I have slowly started introducing them back to each other by feeding them on opposite side of a closed door/now a screen door. They aren’t hissing or growling when they see each other anymore, and seem to be touching noses through the screen mesh. Is it time to let them be together again? I don’t want to ruin all our progress.

    • Hi Ella, you can start letting them out together however for short periods and under your supervision, as soon as you see any sign of aggression separate them immediately. Same for good behavior, if you let them out together for 10mins and they were well behaved reward them with treats.

      I would say start with 10 mins for a few times, and if you notice good behavior from both of them on the long run start increasing the time bit by bit, and don’t rush it 🙂

  5. Hi, I am andrea and I am a hospice nurse and I had a patient who had a cat that she loved very much and I ended up becoming very close to the family and I promised my patient that I would take her cat Lila who is 15 years old in to my home once she passed Recently she has passed and I brought Lila home where I have a two year old cat who is a rescue and a six month old kitten who is also a rescue and it is very important for me for them to get along, but I’ve noticed that they are very territorial of me. I live in a smaller space and I have a camera where I can watch everything they’re doing and as long as I am not in the room and Lila is in the carrier, they don’t seem to mind each other too much, but once I come into the room, they seem to become more aggressive, hiss and growl at each other. I’ve looked at many YouTube videos. I’ve read a lot of articles to try to understand how to introduce them, now my two-year-old cat and my six month old cat it didn’t take long for them to get along. I’m not sure what to do. I’m afraid to let them out all together. Lila the 15-year-old cat. She has kind of a hip problem and can’t really walk all that well and I’m afraid that my 2 year old cat that might hurt her. Saint my six month old cat is a little more accepting of her, but Lila doesn’t want him near her. I want what’s best for all three of them and I will want nothing more than for them to get along, so I can keep your promise and I can love all of them.

    • Hi Andrea, I totally understand the struggle. My advice to you is to not rush the process, keep them separated for as long as they need, let them eat in front of each other while there’s still a separation, reward them with a treat if they finish eating without growling at each other or for any other good behavior.

      Let them switch places, for example let Lila out in the house when you get home for 30 minutes and your 2-year old cat in Lila’s carrier so that they get used to each other’s scent, do not let them interact at any point until you notice less aggression and more acceptance. This may take longer than the usual because you have 2 adult cats, which usually is harder than introducing a kitten to an adult cat.

    • I recently rescued a 9 month old female from a shelter. My 8 year male is an inside/outside cat. Now he won’t come in unless he’s hungry or wants to sleep late at night. I feel this is slowing down the process of both cats getting to know each other. Neither seem happy with each other. Hissing, growling behind closed inside door. They are in separate rooms and I’m trying the steps. I don’t want him to feel kicked out of his own home.

      • Hi Karen, I hope the introduction process works out. Try to keep him in as much as possible until they get along and then he can get back to his routine. Good luck!

  6. Can we start over if we totally messed up and didn’t realize there were steps to introducing a new kitten? Ruby is about 4 months, fixed kitten and we introduced Dexter, about a 3 month old, fixed male. Ruby has been with us for about a month and a half and we thought she would love a friend, so we got Dexter and she HATES him. So is it possible to start the introduction process over?

    • Hi Angie, yes definitely you can start the introduction process over. It should be faster and easier now since some familiarity has been already established! However never rush the process and follow the instructions step by step! 🙂

  7. I have a mama cat that has been in my spare room with her babies, and babies are now fully weaned (they’re about 8 weeks old now). I have slowly been introducing the kittens to my 2 adult cats, and things are going really well. Mama still freaks out when she sees my 2 though. She lunges for them with growling and hissing. She wants out of the spare room really bad, so she is becoming quite an escape artist. I have a baby gate up (slows her down a bit) and I have to put a screen across my hall so she doesn’t see my 2 when I go into the spare room. I have never had an issue introducing cats/kittens to my cats (I foster), so I’m kind of stumped as to what to do. This is mama’s first litter and she was about 9-10 months old herself when she had babies, so I’m not sure if that has anything to do with it. Any advise would be appreciated!

    • Hi Melvin, are you keeping the kittens with their mom still or did you totally separate them from her? If they are staying with her still she could be protective over them hence the difficulty to introduce her to your cats, so try to separate her kittens from her. Another factor that you could consider is first spaying her before trying to introduce her to your cats then do the introduction process again step by step. Hope this helps 🙂

  8. Many thanks for this valuable and comprehensive post. About Warning Signs When Introducing Cats. This is really a very important post for me. Because I have two cats. I have seen them become very aggressive when other cats come around. I was expecting another baby. Your post will be of great help to me. Keep posting like this.

    • Glad you found my guide helpful! Indeed cats are very territorial and don’t like new cats crossing their territory. Introducing new cats is a slow and long process. Congrats for your new baby!

  9. Wow! this was an interesting read. Even cats safeguard what they think is theirs. I guess they share some similarities with human beings. I have observed cats staring at each other, making loud sounds and even fighting when introduced to each other, but I didn’t know what to do to make the introduction easier for them. You article has definitely educated me.

    • I’m happy you found my article useful. You said it right, cats are very territorial and don’t like it when new cats are brought in to their environment. Time and patience are key here, you should always take your time when brining in new cats. Following the process I described will definitely put you on the right track.

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