Aggression in Cats - What Causes It? - Cat Info Detective

Aggression in Cats – What Causes It?

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Welcome worried cat lovers! Skye Blake here, reporting with info about aggression in cats and how you can help them live peacefully.

If you have cats who are fighting each other or biting and scratching you, there are ways you can change this dangerous behavior.

paw prints coming in from a distance

Let’s discover more…

Who Is Skye Blake?

Skye Blake-updated, white background

Skye Blake, Cat Info Detective, is a curious cat researcher (not a veterinarian or behaviorist) who sniffs out expert, reliable sources about cats, studies their information, then passes it on to you! 

Sometimes there’s not enough evidence for easy answers, so Skye gives you all sides, explains the situation as thoroughly and clearly as possible, and links you to experts on each page. 

All sources are at the bottom of each page so you can do more snooping… 

What Makes a Cat Aggressive?

cat yawning, angry or in pain

Aggression is any behavior that threatens or causes harm to others.

Feline aggression can be aimed at anybody… you, your kids, dogs, other cats, their mirror reflection, even inanimate objects.

Cats usually signal annoyance, distress, and aggravation in ways that people can understand… if they’re paying attention.

tabby, white cat hunched, loaf

Twitching tail, flattened ears, eyes staring, pupils dilated, whiskers shifted forward, lowered head, warning growls… all are aggressive signs that will become worse if the threat doesn’t go away.

Think of it as a balloon filling with air until it finally bursts!

Paying attention to these signals gives you the power to de-escalate the situation and let the air out of the balloon.

Curious about what your cat’s eyes are signaling? Check out “Cat Eyes – What Do They Say?

Types of Feline Aggression

tabby, white cat wary, ears flat

We felines always have a reason for what we do… wasting energy on random action isn’t how we roll!

Aggressiveness is intended to make the threat go away, not dominate or be mean.

If aggression is aimed at another cat, a cycle of bullying, intimidation, and fighting begins.

Let’s start by understanding the aggression triggers that cat behaviorists have identified…


scared, fearful cat, startled, alert

Fear is a major cause of aggressive behavior in cats.

Anything a cat sees as a threat to her territory is a threat to her safety, which she must defend.

Her “fight or flight” instincts kick in and she’ll either run or fight to neutralize the threat.

black fluffy scared kitten, fear aggression

The first instinct of a fearful cat is to run, hide and look as small as possible, often settling into a tense hunched “loaf” under your bed.

This posture is defensive and will become aggressive if a cat sees no way of escape or believes something is a threat… whether or not it actually is.

fearful cat hiding

Cats can learn that certain situations are scary, so they might become defensive and strike first even if there’s no real threat.

A scary situation could be when people come suddenly flying in the front door with loud adults, kids, and dogs.

Your cat’s startled and believes there’s a threat even though nobody’s trying to hurt her.


Stuffed animals with medical syringe, vials - vet

Cats are masters at hiding pain and illness because any physical weakness exposes them as prey to any predators in the area.

But if someone touches a sore spot, our instinctive response is to lash out at anyone in reach.

People sometimes do the same thing… when they’re sick or hurt they lash out verbally or physically at everyone around them.

vet looking at cat's eye

Cats can associate specific situations with positive or negative experiences.

An example of this is going to the vet… the smells, people, and sounds can trigger the memory of pain.

The cat can become afraid and lash out even though there’s nothing painful happening.

Black cat in litter box

This can also happen with a litter box.

In the feline mind, the box caused them pain when peeing or pooping (especially with constipation) and won’t get in it again.


sick cat holding thermometer and pills

If your normally cuddly buddy suddenly becomes aggressive, hissing, biting or swiping at you, the culprit could be illness.

Think about it… how happy are you when you don’t feel well?

Just like humans, the tolerance level of a sick cat is much lower than normal.

sick cat vomiting the food

Anything from a toothache to arthritis to cancer can cause your cat misery.

If a normally friendly cat starts hiding or sits hunched up in a tense “loaf” position, it’s time for a vet visit.

The quiet sick cat can be easy to overlook but if someone bothers him, the response can quickly be growls, scratches or bites.

Grey tabby cat sitting hunched with eyes closed

While rare, there are chemical imbalances that sometimes happen in the brain, causing a cat to constantly be on high alert, defensive, and unhappy.

This can only be determined by testing and analysis by a vet.

Once diagnosed, you can work together to determine if there’s a need for psychoactive drugs or other drug therapies.

Syringe, vaccine vials, pills - vet medicine

Sometimes these therapies are able to balance brain chemicals and allow your cat to finally be comfortable and happy in her own skin.

Always get your cat to a vet immediately when any unexplained behavior changes happen.


kittens looking out the window

This happens when a cat gets upset about something, can’t get to the target, and attacks the closest thing to him instead.

The classic example of this is when two cats are sitting quietly by a window watching cat TV.

Suddenly a neighbor’s cat walks through the yard and one cat feels territorially threatened… “INTRUDER ALERT, ATTACK!”

orange, white cat on windowsill looking worried

He can’t get outside to attack the neighbor’s cat, so he turns to the cat next to him and WAP… redirected aggression!

His victim will either run away startled or swat back, which then could escalate into a brawl.

Tabby cat looking in window

A territorial threat from outside can also cause an indoor cat to pee mark around doors and windows in an attempt to send the message… “This is my territory, go away!”.

Discover more at “How to Stop Cat Fights” and “Deciphering Cat Pee Patterns“.

Petting Overstimulation

cat being petted at animal shelter, rescue

Every cat owner knows this one!

You were quietly petting or scratching his back when suddenly, WHAM!

You’re left with a scratched and bitten hand… that hurts!

Person petting tuxedo cat's head, cat biting finger

You may think he’s mean and hates you… but here’s the reality.

A cat’s skin is very sensitive, although some cats are more sensitive than others.

If you pet an area too roughly or start out fine but pet too long, it’s uncomfortable, even painful for your cat.

woman and child with black cat

The only way he can say “stop!” is to swat or bite your hand and run away.

This can happen also when one cat grooms another, although they get the message to stop a lot faster than most humans do.

There may be a warning swat or growl and the other cat stops right away.

person petting a tabby cat's head

It’s important that you find the tolerance limit for each of your cats, then make sure you and others stop petting before that point.

This keeps it a positive experience for you both and, over time, he may learn to tolerate more.

Don’t force it though, or you’ll be back at square one!


Bengal cats sniffing noses

Ownership of territory is a primal need of all cats, including housecats.

It’s when we feel insecure and threatened in our territory that we have trouble.

“Insecurity” is defined by Merriam-Webster as “a state or feeling of anxiety, fear, or self-doubt or “lack of safety or protection”.1 Insecurity Definition & Meaning – Merriam-Webster

3 cats sleeping together

Contrary to popular belief, though, we felines aren’t solitary creatures.

We’re solitary hunters but have social groups, just not the same way as dogs (perish the thought!)

We don’t have one constant dominant alpha cat.

2 orange, ginger tabby kittens sleeping on a chair

Instead, we share territory as long as each cat has enough scent in it to feel safe.

Since cats are very individual, there are those who will never accept other cats, but most can and will if properly introduced to each other.

Discover more at “How Do You Do – Introducing Cats“.


Males (Tomcats)
Cartoon tough injured cat - color

Tomcat fights are brutal and known to cause serious injury or death as they claim females and establish their territory.

Don’t ever try to break them up or get in the middle… you could end up in the hospital!

Some people turn a hose on them, using the water to send them in different directions.

graphic of beaten up tomcat

That, however, only stops it temporarily, since they’ll meet again later.

Male cat aggression has been shown to be 80-90% reduced in neutered tomcats.

The younger the cat when neutered, the less likely any sexual aggression toward other male cats will occur.

wildcats lounging together

Older tomcats may be in a habit of attacking other male cats and might need redirection and other positive training to learn to get along once they’re neutered.

Some might need to be only with females or the only cat in the home.

Toms & Kittens
Maine Coon cat - ginger, standing on log

One other male aggressive behavior is when toms kill kittens, even ones they sired.

There are different theories about why this happens, but the most common one is that newborn kittens look like prey.

Nobody knows for sure, though… no scientific studies have been done to prove any of these theories.

Which leads us to aggressive behavior of queens…

white mother cat with kittens, babies

Mother cats are called queens… and they certainly live up to the name!

Females are not sexually aggressive but once they become mothers, watch out!

A heightened hormonal instinct to protect their young is so strong it can make a mother cat suppress her natural instinct for flight when she feels a threat to her kittens.

tabby mother cat with calico kittens, milk

Instead, she will stand and fight ferociously to drive away the intruder and keep her kittens safe.

Queens within a social group often suckle each other’s young and share protective duties.

This gives the kittens a greater chance of survival and seems to work well, given how many cats there are!

mother cat with kittens

That protective instinct also comes out against people, which is very important to remember when attempting to handle newborn kittens.

Even if the queen is normally your cuddle buddy, she could easily see you as a threat to her babies and attack accordingly.

Pay attention to the warning signs… hissing, growling and even a warning swat mean “back off”.

black mother cat with young kittens

The first month is when kittens are most vulnerable and when mom is most protective.

Experts recommend not trying to handle kittens for the first 2-3 days after they’re born.

Children should be closely monitored if you allow them in the area during this time.

black, white mother cat with kittens

They should be instructed to stay quiet, only watching without touching and not crowding or disturbing the queen.

Some queens are used to having their people around and involved, so they’re more tolerant of humans handling their kittens.

But if the queen sees you as a threat, she may choose to move the kittens to a place she considers safe rather than attack you.

young tabby kitten being bottle-fed

Some people believe that orphan kittens raised by people are more aggressive than kittens raised by their mother, learning to play with siblings.

One study done about problem behaviors in human-raised kittens showed that aggressive behavior or fear doesn’t develop any differently in them than in queen-raised kittens.

It determined that human-raised cats who have a companion to play with and owners who play using wand toys, have little aggression toward people.2“Do Cats Mean to Be Mean?” by Terry Marie Curtis, DVM, MS, DACVB, Decoding Your Cat, by Editors, American College of Veterinary Behaviorists, Houghton Mifflin Harcourt Publishing Co., New York,, pp. 149

Idiopathic (Unprovoked)

confused woman

If you’ve learned the signs of potential attacks and worked to prevent them with redirection, training, and proper play, you should have no more feline aggression.

So, what do you do if your cat’s sitting quietly and suddenly launches a full on, serious attack on your or another cat?

When you have no idea why this is happening, take him to the vet, even though you may have had a checkup done recently.

vet listening to cat's heart with stethoscope

It’s important to rule out physical causes for this behavior or whether it’s an idiopathic (unprovoked) attack without a specific known trigger.

Idiopathic aggression is rare and isn’t something you can diagnose yourself.

More often than not, the situation is one where there’s a trigger that you missed, rather than a true unprovoked situation.

Silver tabby kitten looking scared - on sofa by pillow

Your cat could simply be still upset about something that happened hours or even days before.

This can lead you to misread their behavior as something that has no trigger when it actually does.

This is why it’s so important to learn your cat’s individual purr-sonality and sensitivity to potential triggers.

Medical Therapies
pharmacy-pills - vet medicine

When you understand what triggers your cat, you will be more able to discuss the situation knowledgeably with your vet.

If this behavior is a frequent occurrence, your vet may suggest trying a drug therapy even though there’s no specific diagnosis.

You may want to also discuss the situation with a Board-Certified Veterinary Behaviorist or other highly qualified behaviorist.

generic person - scientist, lab equipment, vet, meds

Your vet should be very familiar with any drugs he recommends and be able to explain…

  • how they work
  • all possible side effects
  • dosage
  • how long to use them
doctor, scientist, vet, pills, capsules, vitamins

It’s important for you to know the effects of the drug so you can watch for both positive and negative changes.

Drug therapies are not substitutes for environmental enrichment, proper play, correct feeding, and training.

Alternative Medicine
graphic of cat getting acupuncture

If you’re hesitant to use drug therapies or they haven’t worked, you may decide to try alternative ideas.

A few of these are…

  • pheromones
  • flower essences
two-yellow-sunflowers-with-clear-glass-bottle - oils, fleas
  • homeopathic medicines
  • animal acupuncture
  • animal chiropractic
vet checking cat's leg

Be aware, though, that while these sometimes seem to have a positive result in cats, they’re based only on anecdotal evidence, not scientifically verified controlled studies.

If you decide to try any alternative therapies, do your homework, know the risks.

Be sure you’re working with qualified specialists and using high quality products.

medicinal essential oils - fleas

There are many questionable claims and frauds in the world of alternative medicine, so be careful if you proceed.

Reputable alternative veterinarians can be a good place to start.

In the USA, these vets are traditionally trained in western medicine but have expanded their training to alternative and eastern medicine.

These techniques are not substitutes for environmental enrichment, proper play, correct feeding, and training.

Is Euthanasia Necessary?

cat looking stern; threats to territory are major causes of pee patterns in the house, how to stop cat fights

If you’re at your wits end and can’t seem to stop cat fights, you may be wondering if it’s best to euthanize an aggressive cat.

This could be best for the sake of other pets, your human family, and your own sanity.

But the odds are slim that you have a cat who truly can’t live in peace in your home.

cat yawning, angry or in pain; how to stop cat fights

Before making a final decision, discuss the situation with your vet and a qualified cat behaviorist, if possible.

Their advice is valuable when dealing with complex situations that seem to have no answers.

Pam Johnson-Bennett is a Certified Animal Behavior Consultant and a pioneer in feline behavior.

dark tabby, white sitting hunched in a loaf

She says this about euthanasia…

“In the many years I’ve been doing this, I have come across a couple of cats who had to be euthanized due to severe aggression (the cause in those cases was an untreatable medical condition). It’s not a decision to be rushed into.”

Think Like a Cat, How to Raise a Well-Adjusted Cat – Not a Sour Puss” by Pam Johnson-Bennett, Certified Animal Behavior Consultant, Penguin Books, Penguin Group (USA) Inc, New York, NY, 2000, 2011, pp. 145-6

This video is helpful for understanding the types of aggression and options for dealing with them…

“8 Types of Cat Aggression Explained!” by Jackson Galaxy, May 1, 2021

Moving Forward

2 cats sleeping together in sunlight, window

Now that you understand the causes of feline aggression, you can learn how to have a peaceful home for everyone.

Discover more at “How to Stop Cat Fights“, “How Do You Do – Introducing Cats“, and “Playing With Cats the Right Way!“.


Sources used on this website are either primary or secondary.

Primary sources are always preferable and have the most reliable information because they’re original and directly referenced.

Scientific abstracts and data are good examples of primary sources.

Secondary sources are weaker because they usually consist of opinions or articles that give no sources of their own.

However, sometimes they refer to primary sources.

When I use secondary sources, most are those with some authority, such as veterinarian or cat behaviorist books and articles.

List of Sources

“Bad Moods”, Chapter 13, Cat Wise by Pam Johnson-Bennett, Penguin Books, Penguin Random House LLC, New York, pp. pp. 242-257

“Do Cats Mean to Be Mean?” by Terry Marie Curtis, DVM, MS, DACVB, Decoding Your Cat, by Editors, American College of Veterinary Behaviorists, Houghton Mifflin Harcourt Publishing Co., New York,, pp. 143-164

“Feline Aggression: Accepting and Managing Your Cat’s Inner Wildcat”, Chapter 7, The Cat Whisperer by Mieshelle Nagelschneider, Bantam Books, The Random House Publishing Group, New York NY, 2013,, pp. 125-170

How to Train Your Queen Cat to Avoid Aggression” by Amy Shojai, The Spruce Pets, Updated on 03/03/19

“Hissy Spitty Kitties…”, Tiny But Mighty by Hannah Shaw, Plume, Penguin Random House LLC,, pp. 148-158

“Sensory and Neural Behavior Problems”, Feline Behavior: A Guide for Veterinarians by Bonnie V. Beaver, DVM, MS, Dept. of Small Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, Texas, W.B. Saunders Co., Philadelphia, PA, 1980, 1992, pp. 43-47

Think Like a Cat, How to Raise a Well-Adjusted Cat – Not a Sour Puss” by Pam Johnson-Bennett, Certified Animal Behavior Consultant, Penguin Books, Penguin Group (USA) Inc, New York, NY, 2000, 2011, pp. 134-147

Total Cat Mojo“, by Jackson Galaxy with Mikel Delgado, PhD, Tarcher Perigree, Penguin Random House, LLC,, New York, NY, 2017

Updated April 1, 2024

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