The Humane Society of the United States
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Aggression between Cats

  • The first step in helping resolve aggression between your cats is to understand its source. Mike McFarland/The HSUS

Cats are very territorial creatures and can fiercely defend their turf. And even cats who have gotten along in the past may sometimes start to rub one another the wrong way. But you can help get their relationship back on track.

Adding a second cat

Many people adopt a second cat thinking that the resident cat will be appreciate the companionship. This is a risky move. The fact that your cat is sweet and loving with you doesn't mean they're going to be sweet to another cat. Because your cat is territorial, it's not uncommon for the addition of a new cat to the household to create some strife.

Although you can increase the chances that they will get along or at least tolerate one another by making proper introductions, there's no way to predict whether cats will get along with each other. Unfortunately, there's no training method that can guarantee that they ever will. But it's usually possible to negotiate a truce, even if your cats don't become best friends.

Avoid conflict when bringing a new cat into the family by carefully introducing your cats »

Types of aggressive behaviors

Territorial aggression

This occurs when a cat feels that an intruder has invaded their territory.

  • A cat may be aggressive toward one cat (usually the most passive), yet friendly and tolerant with another.
  • Problems often occur when a new cat is brought home, a young kitten reaches maturity, or a cat sees or encounters neighborhood cats outside.
  • Typical behavior includes stalking, chasing, ambushing, hissing, loud meowing, swatting and preventing access to places (such as the litter box, bedroom, etc.)
  • Female cats can be just as territorial as males.

Learn how to help your cats get along »

Inter-male aggression

Adult male cats may threaten, and sometimes fight with, other males. This is more common among unneutered cats. They may fight over a female, for a higher place in the pecking order, or to defend territory.

Cats stalk, stare, yowl, howl and puff up their fur (picture the arched back of the Halloween cat) to threaten each other. If one does back down and walk away, the aggressor, having made his point, will usually walk away as well.

If no one backs down, cats may actually fight. They may roll around biting, kicking, swatting or screaming, only to stop suddenly, resume posturing, fight again, or walk away. If you see signs that a fight may occur, distract the cats by clapping loudly, tossing a pillow nearby, or squirting them with water. These actions can also be used to break up a fight. Keep your distance, and never put body parts in the middle of a fight; you could be injured.

Defensive aggression

Defensive aggression occurs when a cat tries to protect himself from an animal or human attacker he believes he can't escape. This can occur in response to the following:

  • Punishment or the threat of punishment from a person
  • An attack or attempted attack from another cat
  • Any incident that makes the animal feel threatened or afraid

Defensive postures

  • Crouching with the legs and tail pulled in under the body
  • Flattening the ears against the head
  • Rolling slightly to the side

Approaching a cat in this posture is likely to cause an attack.

Redirected aggression

Cats can sometimes direct aggression toward another animal, or even a person, who didn't initially provoke the behavior. For example, your cat is sitting in the window and sees an outdoor cat walk across the front yard. They gets very agitated because that cat is in his territory. You pet them; they turn and bite you. Your cat doesn't even know who you are at that point—they are so worked up about the cat outside that they are attacking the first thing that crosses their path. It's important to respond to this redirected aggression in a way that will keep both you and your upset cat safe.

Follow these steps if your cat suddenly attacks you or another cat for no reason »

Consult with a veterinarian

If your cat has suddenly become more aggressive than normal, your first step should always be to contact your veterinarian for a thorough health examination. Cats often hide symptoms of illness until they're seriously ill; your aggressive cat may be feeling sick and taking out their misery on others. 

If your cat gets a clean bill of health, consult your vet or an animal behavior specialist for help. A behaviorist will advise you on what can be done. You may need to start the introduction process between two cats all over again, keep the cats in separate areas of your home, or even find one of the cats a new home if the aggression is extreme and can't be resolved.

Consult with your veterinarian about a short course of anti-anxiety medication for your cats while you're working on changing their behaviors. Never medicate your cat on your own.

Prevent future fights

This could mean keeping the cats separated from each other while you work on the problem, or at least preventing contact between them during situations likely to trigger a fight.

Spay or neuter your pets. Spaying and neutering can greatly reduce aggression in cats. The behavior of one intact pet can negatively affect all of your pets.

What to avoid

  • Don't count on the cats to "work things out." The more they fight, the worse the problem is likely to become. To stop a fight in progress, make a loud noise (like blowing a whistle), squirt the cats with water, or throw something soft in their direction.
  • Don't touch them, or you might get seriously scratched or bitten. Seek medical attention if you're injured.
  • Don't punish the cats involved. Punishment could cause further aggression and fearful responses, which will only make the problem worse. You could even become a target for redirected aggression.
  • Don't add more cats. Some cats are willing to share their house and territory with multiple cats, but the more cats who share the same territory, the more likely it is that some of your cats will not get along with each other.

Cat friendship is a feline mystery

Many factors determine how well cats will get along with one another, but even animal behavior experts don't fully understand them.

We do know that cats who are well-socialized (those who had pleasant experiences with other cats during kittenhood) will likely be more sociable than those who haven't been around many other cats.

On the other hand, "street cats," who are in the habit of fighting with other cats to defend their territory and food, might not do well in a multi-cat household.

Adapted from material originally developed by applied animal behaviorists at the Dumb Friends League, Denver, Colorado. All rights reserved.

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