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5 Warning Signs When Introducing Cats

two cats in bedroom
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Cat lovers have no trouble listing the amazing attributes of their cat – like their furry friend’s intelligence, humor, and ability to entertain, to name a few. 

On the other hand, we all know some cats can also be aloof and/or territorial. The latter characteristics are often tricky when it comes to introductions, whether to a new cat or other new pet, or even other people. 

“It’s important to note that cat introductions can be very challenging and time-consuming,” says Dr. Audrey Wystrach, co-founder and co-CEO of Petfolk animal clinics. “It’s a process that requires time and patience.” 

Here are some things to keep in mind if your cat has some introductions coming up in the future.

Introducing Cats: The Basics

Whenever your cat will be around new cats, it’s essential that you observe your feline friend’s cues. 

“It’s very important to pay attention to the details when introducing your cat to another animal or person, because your ability to understand what your cat is experiencing and feeling is imperative for their comfort and happiness,” says Lauren Parsch, a certified cat behaviorist and practicing cat behavior consultant. “If they’re experiencing discomfort or viewing the interaction as negative, this is going to shape their future experiences and relationships with this person or animal, and potentially even with other people or animals.”

Getting that first introduction right is important, so be sure to research the steps to take both ahead of time and during to ensure everything goes as smoothly as possible. 

First, if your cat generally spends a lot of time under the bed or couch, in the closet or squeezed above the fridge, Parsch suggests working to build up their confidence and lessen their fear level before trying to introduce them to other cats.

If you do believe your cat is ready to meet another feline, check out our essential techniques to implement when introducing them. For example, designating a safe space for any new pet entering the picture is crucial, as is making sure your current cat has all the things that make them feel safe and happy readily available when the introduction occurs. 

5 Warning Signs When Introducing Cats

Two cats fighting

Once you have a plan for cats to meet, be on the lookout for the following warning signs when introducing cats that may signal trouble is afoot:

Negative Body Language

Our cats tell us a lot about what they’re thinking with just a few small moves. For example, “the most common dynamic that will develop between cats is the prey and predator dynamic,” says Parsch. “Cats are both prey and predator in the wild, so it’s very instinctual for them to assume one of the roles.” 

Your cat might display the following prey-type body language upon seeing — or even just smelling — another animal or strange person. These can all be signs of a fearful, anxious, or defensive cat:


A cat that’s hiding is often doing so for one of two reasons:

Stress. If your cat is hiding underneath the furniture or on top of the fridge, they’re likely stressed out from a new introduction. This is particularly dangerous, since “cats can even develop stress-related inflammation in their urinary tract that can mimic the signs of urinary tract infections,” explains Parsch.

Playtime. On the flip side, a cat that’s hiding behind something — likely combined with other movements like getting low to the ground, dilated pupils, forward ears, tail tapping or twitching, and a wiggling butt — is probably preparing to pounce in a playful way, like they would with a toy. 

Verbal Cues

The following cat verbal cues are warning signs when introducing cats. Most often associated with anger or fear:

Be sure to take note of any of these noises – or any combination of them – when making your introductions. If you notice any negative verbal cues, stop the introductions and try again another time.  

Urine Issues

Cats may develop litter box avoidance or urine marking habits when they feel threatened. “Cats identify and interact with their surroundings largely through scent,” says Parsch. “Urine marking is a desperate attempt for a cat to feel safe and claim a sense of ownership over their territory.” 

For example:

Litter box problems. When introducing a new animal or human, your current cat may spray or urinate outside of their litter box.

Urine marking. They may also urinate on items and areas that heavily hold the cat parents’ scent, like the sofa, the bed, or their shoes, as a means of marking their territory.

Resource Guarding

If your cat feels there aren’t enough resources to go around, they may resort to blocking the newcomer from having access to certain things. 

Signs of resource guarding may include:

  • Laying across doorways/entryways
  • Blocking entrances to the litter box
  • Blocking food or water
  • Using intimidating body language (like puffing up or arching) and hissing to get another animal away from a coveted resting spot

Prey or Play: How To Tell The Difference

Cats sniffing each other

It can often be difficult to tell the difference between a cat that’s playing and a cat that’s fearful or exhibiting dangerous behavior. 

For example, “a cat that’s growling or hissing is usually demonstrating a fear response and is assuming the role of the prey,” says Parsch. “If they decide to run and try to hide, this can trigger a predator response in the other cat, who will instinctually chase the prey cat. The other cat could then act in an aggressive way, or a playful one.” 

Talking to your veterinarian or having a cat behavior professional examine your cat’s body language can help you further determine their true intention.

Introducing Cats: What to Do When It Goes Wrong

Although a little hissing or growling is normal, Parsch suggests redirecting your cat’s attention to something positive if you notice warning signs when introducing cats. “If they continue hissing or growling [and] have the body language mentioned previously, and you’re unable to draw their attention from the other cat with food or a toy, separate them right away,” she advises. “It’s much easier to keep the exposure very short and sweet than to try to push it and create a negative association.”

In general, the goal should always be to build up positive experiences with that person or animal.

How to Tell When it’s OK to Try Again

After an introduction has gone awry, it can be difficult to determine when to try again. Much of it will depend on whether an actual fight occurred between the two animals, says Parsch. 

“Once a fight breaks out, it’s going to be more difficult to backtrack,” she explains. That’s why your goal during any introduction should always be to pay attention to signs — even subtle ones — and stop extreme behavior from occurring in the first place.

If a fight doesn’t break out, try separating your cat from the new cat for awhile. If they can still smell each other and there are no signs of agitation from either one, you can try again. 

To help animals smell each other when separated, “use a soft brush or clean sock and gently stroke the face, head and shoulders — where the cat secretes its friendliest pheromones — of one of the cats, and then present the brush to the other cat,” suggests Parsch. “If there are no signs of hostility or fear from either cat when presented with the other cat’s smell, you can try to restart the introduction process.”

In general, keep in mind that it’s better to go too slow than to go too fast when introducing your cat to another cat. This makes it easier to always stay one step ahead of those warning signs. Good luck!