Warning Signs When Introducing Cats

Introducing two cats can be a tricky process that can prove stressful for both the cat and owner.

To avoid stress and prevent the two cats from coming to blows, it’s really important to familiarise yourself with some of the behavioral cues that prelude physical confrontation.

Introducing Cats – Warning Signs

Here are some of the most common warning signs you should look out for when introducing two cats.

Cat Hissing


Cats hiss when they are scared, angry or feel threatened. It is a defensive behavior to warn other animals to back off.

When cats meet, they’ll often hiss or growl at each other as they try to establish their territory. The hissing occurs when one cat intrudes on the other’s space.


Cats sometimes make a sound that resembles coughing or rumbling when they see another cat. This is often used as a form of communication to warn other cats about danger.

However, during introductions, the coughing and/or rumbling could be a territorial warning from one cat to the other.


Cats will usually growl when they feel threatened. They may also show their teeth, bite and hiss in an effort to scare off an intruder.

So when another cat is introduced, the growl is very likely to be an indicator of fear or aggression. This kind of behavior is very common when introducing cats.

Flattening of Ears

When cats meet each other, they’ll often flatten their ears. This means the cat is either nervous or angry and attempting to exert its dominance of the other.

The behavior is often accompanied by prolonged staring, standing upright and raising the tail while dropping the tip.

Puffing Up of Fur and Tail

When cats arch their back and puff up their tails they likely feel threatened.

The primal instinct here is to look bigger and more intimidating when they meet another cat. Projecting its size makes the cat a less desirable target for the rival feline.

In essence, puffing up of the fur is a defensive posture that often recedes once the cats become more comfortable with one another. But during initial introductions, it’s most certainly a warning sign to look out for.

Cat Staring

Pupils Dilate

This is a reflexive response that’s part of a cat’s ability to see better than humans in low light conditions. Their eyes are equipped with many complex features such as the tapetum lucidum.

This increases the amount of light available for vision and also enhances night vision by reflecting blue-green wavelengths of light back through the retina.

But keep in mind that cats’ pupils also dilate when they’re excited, surprised or fearful.

Staring Competitions

With new introductions, staring indicates that each cat is trying to establish dominance over the other. This prolonged sizing up can lead to confrontation.

Twitching Tail

Twitching tails indicate emotions like fear, excitement or happiness. In relation to meeting other cats for the first time, the most common theory is that the twitchy tail is used to communicate dominance.

Cats will raise their tails up high and then quickly lower them again in order to show the other cat that it has the power.

Hiding and Fleeing

It’s very common for cats to hide or flee from other cats. This may be because they are scared or just want to be left alone.

A lot of times, it because the other cat is bigger or more dominant.

In our present context, the most likely reason that an indoor cat is hiding or fleeing is that the other feline has established the dominant role.

While this isn’t exactly the ideal scenario if you’re looking for your cats to get along, many house cats that live under the same roof, peacefully co-exist under such conditions.

However, if you’ve just introduced them, keep a close eye on the submissive cat, making sure that he’s feeding properly and using the litter-box.

Cat Doesn’t Use Litter-Box

Litter-box  neglect could be due to a number of reasons, ranging from lower urinary tract disease (FLUTD), bacterial cystitis, kidney failure, liver disease or diabetes.

Anxiety and stress are also known to prevent cats from using their litter-boxes. This may be caused by the other cat.

Cats are also known to refuse a litter-box if another one has used it. The solution here would be to install another box to cater for both.

Cat Stops Feeding

Cats are known to be territorial and may stop eating when they see other cats nearby. It is not clear why this happens but it could be that the cat feels threatened.

It may also be due to increased competition for food, or a change in the type of food that is being offered to them.

Cat Confrontation

Cats Bite and Attack Each Other

This is aggression in its purest sense and one of the most overt forms of territorial behavior in cats. A cat that bites another may be trying to exert its dominance.

It may also feel threatened and perhaps cornered, lashing out in an attempt to flee the area. This kind of behavior may require your intervention.


Sadly it’s sometimes the case that cats just won’t get along, no matter how hard you try. This may be out of defensive territorial instincts, or a lack of socialization skills.

It might also be due to a health issue or simply because they were born into different litters. Nevertheless, the above advice will hopefully be of some help.

Remember to introduce the new cat into a new environment slowly. This will allow both felines to get used to each other. Don’t rush the process and try to be patient. Good luck!

Useful Resources

American Humane – Introducing Cats to Cats
Humane Society of the United States – How to Introduce New Cats to Your Home
iCatCare – Introducing an Adult Cat to Your Cat

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