13 Warning Signs When Introducing Cats: How-To Guide Tips and More!

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Warning Signs When Introducing Cats

Once you’ve adopted or rescued a cat, it wouldn’t be long enough before you desire a second cat. You would either want this so that your resident kitty will have a new feline friend, or you simply want to grow your feline family.

However, unlike dogs, cats are territorial animals. A lot of things could go wrong when introducing a new cat at home. Hence, you should know how to identify the warning signs when introducing cats to prevent a catastrophic cat fight.

Warning Signs When Introducing Cats to Each Other

When you bring a new cat home, it’s normal for you to expect your current cat to love the idea of sharing his own space and resources with another cat. In an ideal world, this should be the case. However, realistically speaking, cats, being territorial and solitary animals, hate it when other cats intrude into their area uninvited. Hence, the presence of a new cat at home can frighten them and make them defensive, and even aggressive toward the newcomer.

However, with proper introductions, you, as a cat owner, may decrease the chances of a hostile meeting, and increase the likelihood that your two cats will get along with each other the soonest time possible. Nonetheless, even if you follow the recommendations by the experts and cat whisperers online and in your neighborhood, one of the cats may still act aggressively toward the other.

That is why it is important to manage the first few meetings, which also allows you to spot certain warning signs that may easily escalate to long-term or even permanent hostile conditions in your multi-cat household.

1. Your Cats Are Staring At Each Other

Upon introduction, you may expect your two cats to look at each other for a while. If your resident cat gives the newcomer a prolonged stare, it may indicate that he is slowly developing aggression towards the other cat.

Soon, your cat may attack the new cat to drive it away from his territory. Once the tension has escalated to this point, you should place your two cats in separate rooms to avoid fighting. So, before your cats even start to get physical, it’s already a warning sign for you to intervene and separate them for a while once they give each other a hard look, or once they stare at each other without blinking. A prolonged stare is an early sign that your cats are sizing each other up.

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2. Your Cats Are Hissing

A hissing cat signals something to back off because it is frightened, threatened or both. Fortunately, hissing is quite acceptable during the introduction stage.

One or both of your resident cats may hiss when you introduce a new cat to the same household. You can relate this noise to a snake hiss or the sound of air releasing from an automobile tire. Your cats may hiss to convey their dread, contempt, and discomfort at being close to one another.

3. Your Cats Are Growling and Snarling

From hissing, the tension between your two cats can escalate and lead them to growl and snarl at each other. A growl is a low rumbling sound. It’s a distinct warning sound that expresses unhappiness, aggression, or fear. And a growl can easily intensify to a snarl, a sound that is similar to a growl, but only louder and with a higher pitch.

4. Your Cats Are Wailing or Screaming

Cats may begin to meow or whine in a low voice when they're upset. Wailing and screaming may result from this. The cats' tolerance level has been reached if it has come to this. To relieve everyone's worry, they must be separated right away.

5. Your Cats May Start Attacking or Biting

When upset cats are left on their own in the same room, the early warning signs, such as growling, snarling, or screaming can lead to a physical fight. And before you know it, furs are already flying in the room. You definitely don’t want this to happen. Hence, before the tension even reaches this point, it’s best to separate the two cats already.

Moreover, some cats may also start attacking each other during the first meeting, even without expressing their disgust through hissing and/or wailing. This warning sign indicates that your cats may need more time to adjust to each other’s presence, and eventually get along. And your deliberate intervention would also be needed.

6. Your Cats’ Pupils Are Dilated

Just like us, humans, cats also experience a fight-or-flight response, which propels them to act impulsively, experience a jolt of adrenaline, or an extraordinary push to do something within a millisecond.

And during instances where the fight-or-flight reflex is activated, such as in the presence of an intruder, a cat’s pupils will dilate so they can see clearly what’s happening. So, if you introduced your new cat to your resident cat in broad daylight, and you notice that his pupils are dilated, it could mean things aren’t going well.

When your cats first meet, you can notice that their pupils enlarge. It shows that they are enthusiastic about the circumstance. They show signs of dread or depression by the dilation of their pupils. When your cat’s eyes are dilated, it can be their way of way communicating their anxiety about the sudden introduction. It's a hint that your feline companions are still not ready to mingle with each other.

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7. Your Cats Are Twitching Their Tails

The sharp left-to-right twitching of a cat's tail typically indicates eagerness, displeasure, or growing irritability. Tail-twitching is one of the most typical indicators that trouble is developing, which is common in multi cat households.

8. Your Cats Are Flattening Their Ears

A cat that flattens its ears against its head is either scared or hostile. It can also occasionally indicate anger. Either way, flattened ears are warning signs that your resident cat perceives the other cat as a threat or an encroachment on his territory.

9. Your Cats Are Puffing Up Their Fur, Bristling Their Tails, and Arching Their Backs

Typically, this serves as both a warning to the other cat and a statement of authority. Cats strive to look as enormous and frightening as they can by inflating their hair, bristling their tail, and arching their back.

10. Your Cats Are Hiding From Each Other

It's typical for cats to hide from one another when they first meet. The less dominant cat typically hides out of fear when the more dominant cat approaches. To avoid confrontation with the more dominant cat, your less dominant cat may attempt to scurry under the bed or sofa. Alternatively, the more dominant or aggressive cat may begin stalking or chasing the other cat to drive it away from his territory.

11. Your Resident Cat May Stop Using His Litter Box

Stopping to use the litter box is a strong sign that a cat is under stress. Your resident cat will completely avoid his litter boxes if they are too close to a cat they see as a threat. While litter box avoidance might not result in a fight right away, it's certain that your two cats aren't getting along.

12. Your Cats May Stop Eating

A quick or sudden introduction of the new cat to your current cat may make the latter uncomfortable and threatened, and as a result, he may stop eating. This is especially true if you feed your new cat in the same room where your resident cat eats, rests, and sleeps.

13. Your Cats Refuse to Coexist With Each Other

Sometimes, despite your best attempts, your cats may not get along. There is a high chance that they may not stand each other and that they may grow nastier with time. They could exhibit resistance to socializing, eating, or playing.

This circumstance suggests that your kitties require a break. It might be beneficial if you kept them apart and then properly reintroduce them after a few days. You might ask your veterinarian or an animal behaviorist for assistance in putting things right this time around.

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How to Introduce Cats

Despite the challenges attached to having many cats at home, we cannot deny that a lot of pet owners still consider getting a second cat sooner or later. This may sprout from one’s desire to provide the best life to their cats considering that felines that live in a multi-cat household receive more mental stimulation, interaction, and exercise.

However, as mentioned earlier, a proper introduction is crucial if you want your resident cat and new cat to get along the soonest time possible. Below are some steps that you can take to avoid tension in your household, especially if you have a dominant cat with aggressive behavior.

1. Choose The Right Cat

Oftentimes, choosing a cat to join your household involves some luck, especially if you are adopting or rescuing a kitten. A younger cat still has a lot of room for changes not just in their physical appearance, but more so in their personality and overall disposition. Nonetheless, some general pointers can guide you in increasing your chances of picking the right cat to join your household.

First, you may want to match older cats with young cats. When you bring home a kitten or immature young cat, your resident cat is less likely to feel threatened. There is a higher chance that he will accept the new cat after a thoughtful introduction. Given their age and background, the older cat will probably be the top or dominating cat in the new dynamic. A young adult cat and a kitten added to your family can frequently result in a positive outcome.

It may be simple to introduce a young cat or kitten to your elderly resident cat, but it might not be a smart choice in the long run. The younger cat will likely have too much energy and fun for the older cat over time, and this could eventually distress the elder cat.

Matching cats of the same age can also work with the aid of a proper introduction. However, power disputes and territorial possessiveness should be avoided, so keep a close check on things. Cats that are similar in age have a higher propensity to become hostile, especially if they do not scare one another like male cats.

Aside from age, a matching personality is another factor that plays a huge role in any successful introduction. The addition of another cat to your home is unlikely to be a sensible decision if your cat is shy, combative, or socially awkward; both cats or one of the groups will likely experience unneeded stress and would have been better off being alone. Similar reclusive cats are prone to bring about tension and infrequent outbursts of anger in your home.

Matching your cat with another cat that exhibits comparable traits, such as being playful, easygoing, and confident, is likely to be successful in the long run. If your cat is frightened or lacks confidence, you might want to work on boosting his self-esteem before expanding your feline family.

Next to age and personality, you may also want to consider the gender of the cat that you are planning to adopt or rescue. Sometimes it makes sense to pair female cats with an already-existing male cat. A female cat is less likely to intimidate a male cat.

On the other hand, introducing male cats can be extra challenging. If you are leaning toward this direction, you must consider the two cats’ personalities. You should also ensure that you have enough space for your cats to claim as their territories.

The final element that can affect a good introduction if you are determined to pair up males and are confident that their personalities won't clash is bringing a younger male cat into the home. A younger cat will typically be more adaptable to his place in the social hierarchy.

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2. Set Up Your Home Properly

Preparing your home for the arrival of your new cat is another important step to facilitating a successful introduction, and fostering a comfortable living environment both for your resident cat and your new feline companion.

Ideally, your new cat should have his own room. And the separate room must contain all of his necessities from his litter tray, bed, scratching post, cat trees, food bowl, water bowl, necessary cat food, enough water, and a few toys to keep him stimulated. It’s also best if you can provide a room with a window where your cat can observe the birds outside and his surroundings.

This separate room will be your cat’s temporary haven during the initial phase of the introduction since you don’t want your two cats to meet each other on day one. Hence, as your new cat may spend most, if not, all of his time here for some time, you’d want him to be as comfortable, happy, and cared for as possible.

To keep your new cat secure and at ease during this transition period, experts also advise installing Feliway diffusers inside his room. After a few days, you can switch your cats' rooms. By doing this, your cats can smell and hear each other, and they will become more curious about one another. Don't encourage direct contact amongst your cats at this time.

Preparing your home can help foster a welcoming living environment for your new cat, and facilitate a successful introduction the soonest time possible. Other ways that you can do this are by placing additional litter trays around your house or apartment, increasing available territory (such as the addition of cat trees, walkways, perches, etc.), and ensuring that your house has enough escape routes for your two cats not to be cornered easily.

3. Stick to a Regular Feeding Schedule

Food is a precious resource, and having it available all the time may tempt one cat to want to claim it for himself. Hence, you should avoid free feeding, even just until your new cat has been successfully introduced. 

4. Use Food to Create a Positive Association Between Your Cats

Aside from being a vital resource, food can also be used to create a positive association. When cats eat, we can say that they are having a good time. Hence, you can use mealtimes to introduce your new cat. Once you've established a regular time for eating, you may use it to encourage contentment that your cats can identify with each other's companionship.

Moreover, you can also place your cats’ food bowls on either side of a closed door. You can move the bowls farther away if they won't eat. The food bowls should be gradually moved up against the door so they can sense each other but not see each other. Take your time before replacing a door with a barrier they can look through during feedings.

5. Get Them Used to Each Other’s Scent

Cats communicate with us, humans, and their fellow feline buddies in a variety of ways, including odors. And one of the key ingredients to a successful introduction is by leveraging the power of scents. Bring bedding or another object that has the fragrance of your current cat when you pick up your new cat. Even before your pets actually meet, this will aid in accelerating the introduction process.

As soon as you arrive home, you should start switching the bedding between your two cats to allow their scents to mix. This facilitates the acclimatization of your two cats or helps them to become familiar with each other even before their first meeting.

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Things to Consider Before Rehoming a New Kitty

When introducing cats to one another, there are a few additional factors to take into account. By heeding these considerations, you can ensure the health and safety of your two cats, and increase the likelihood that they can get along well with each other within the shortest time possible.

Never Introduce an Unvaccinated Cat

Don't mix your resident cat with a new, unvaccinated cat. You must get the new cat in your home vaccinated first, and clear of fleas, mites, and other parasites before introducing him to your existing pet.

Never Introduce Your New Cat to Your Resident Cat Immediately

Being hasty could turn out to be completely incorrect. If you do this, your current cat will feel intimidated and become hostile toward the new cat in an attempt to get rid of him or to drive him away. Therefore, keep the new cat in a different room for a few days before introducing him to your resident cat.

Don’t Let Your Cats Fight

When introducing the cats, always keep an eye on them. You must separate the cats right away if any of them act aggressively or try to fight the other cat. Never allow them to fight since it could become extremely aggressive and dangerous for their lives.

Introduce Your New Cat to The Most Dominant Cat First

While this may sound unusual, this is actually a better way to control the tension inside your house, particularly if you have multiple resident cats at home. As always, you should do the introduction of the new cat to the most dominant resident cat or alpha cat slowly.

Tension will dissipate after the dominant cat accepts the newcomer, and the other cats will do the same. Again, you should be careful not to rush when doing this. Always introduce while using the right technique and taking enough time.

Never Force an Introduction or Let Them Sort Things Out Between Themselves

Whatever you do, you should never simply put your new cat in a room alone with your resident cat and expect the two of them to work things out on their own. Never force an introduction. And it’s a cardinal mistake to assume that they will automatically be forced to socialize once they are left alone unsupervised in an enclosed room.

A proper systematic introduction is essential for your cats to get along well the soonest time possible, and to prevent anyone from getting harmed along the way. If you force an introduction, chances are your cats will refuse to coexist.

And when this happens, your day will always be filled with constant fighting and aggressiveness between your two cats. Eventually, you may have to let go of one of your cats or place them in separate rooms for an indefinite time.


The process of introducing two cats takes time, patience, and vigilance. Frequently, it can be annoying, especially if the two cats act aggressively toward one another. And speaking of aggression, it can escalate quickly to a catastrophic catfight. Hence, as a cat lover and a cat owner, you should heed the warning signs mentioned above to de-escalate tension and prevent a fight.

Aside from the physical altercation, one adverse effect of not paying attention to the warning signs is that it will most probably take time for your cats to get along. You may even need to re-introduce them. But still, this is not a guarantee that your cats may learn to accept, more so, to care for, and love each other.

If your cats already had a rough start, it may be harder for them to develop a tight bond. They may eventually coexist, but they may not be that close to each other.

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