Cat Aggression Toward Other Cats: Causes and Prevention

Are you trying to figure out how to handle cat aggression toward other cats? If cat fighting is occurring in your home between cats who previously lived together without altercations, the first step is to take them to your veterinarian for medical evaluation. Medical problems can cause a cat to be in pain, grouchy, or confused, which increases the likelihood for aggressive behavior. 

If a medical evaluation reveals no abnormalities, the following recommendations might help your cats to resolve their differences. These recommendations can also be helpful for cats who have been introduced to each other recently and are not getting along.

Separate the cat with aggression from the other cat

If one cat keeps attacking another cat, the first step is to separate the cats from each other completely — in separate areas of the home. Do not allow them to paw at or smell each other through a door. If they must be in adjoining rooms, place a barrier at the bottom of the door. Ideally, though, you should confine them in separate parts of the home where there is no opportunity for contact. 

Provide each cat with food, water, a litter box, a comfortable place to sleep, and regular interaction with you (playing and/or petting). It is very important to make certain that you are providing each cat with enough exercise and playful interaction. Often, fights occur when one cat wants to play and the other cat doesn’t. So if you can provide the playful cat with enough exercise, this can eliminate the cat fighting problem.

Cat Behavior Modification and Counter-Conditioning

Look for cat fighting causes and solutions

Why do cats fight with other cats? There can be many potential triggers that lead to cat aggression. For example, your cats might fight when they both want attention from you, or they might become territorial and fight over preferred resting places. They also might fight when they see another cat outdoors.

Before you reintroduce your cats (see below), create a plan for how to minimize cat fighting triggers. If the cats primarily fight over resources, such as access to food or resting places, provide them with multiple sets of resources in different areas of your home. For instance, because a cat will find it much more difficult to guard four food bowls rather than one, aggression is much less likely to occur if you provide more bowls. If the cats attack each other after seeing another animal outdoors, block visual access to the outdoors. Opaque privacy window film works well in this situation.

If the cats are fighting over attention from you, you can teach them that this behavior is not rewarding — that it drives away your attention instead. You can do this by paying close attention to the warning signs of anxiety and aggression, which include dilated pupils, growling, a direct stare at the other cat, tense body posture, and a swishing tail. When you see these signs in your cats' body language, get up from what you are doing and leave the room. The cats will be left with nothing to fight over.

It is crucial that you leave the room at the first signs of anxiety. If you wait too long, the cats will be so aroused and upset that your presence will no longer be important; they will fight despite the fact that you are no longer in the room. If you are unable to recognize the early signs of an altercation, do not attempt this technique.

Another technique you can use to prevent a fight is to teach the cats to come when called. When you see signs of anxiety, you can call them to you and reward them for their good behavior. Keep a box handy containing special toys or treats that your cats really like. After calling the cats to you, play with them individually or give them each a food reward.

Teaching a cat to come is fairly simple. At every mealtime, when you start going toward the area where the food is located, say “[kitty’s name], come.” Your cat will soon associate mealtime with the word “come.” After one week, start saying “come” at random times during the day. When your cat comes, give them a special treat or play with them with their favorite toy. Practice several times per day. You are teaching your cat that when you give the cue “come,” they're always rewarded. The cat learns that it is much more worthwhile for them to come to you than to fight with the other cat. Make sure that you always reward the cat when you call and they come to you.

Reintroduce the cats

After you have decided what technique to use to prevent aggressive incidents, it is time to reintroduce the cats to each other. Start by allowing the cats some access to each other. Situate each cat on either side of a door adjoining two rooms, and let them smell each other through the crack at the bottom of the door.

Next, feed each cat a small bowl of special food (such as canned food or a small amount of tuna) within about five feet of the door. After the cats are eating for a few seconds, open the door between the rooms. If the cats show warning signs of aggression, close the door immediately and remove the food. Wait a while before you try again, and when you do start with the food bowls farther away from the door.

The more frequently you are able to do this exercise, the more quickly your cats will progress, but aim for a minimum of twice daily. Over time, move the cats closer to the door until the cats are able to eat side by side without behaving aggressively. You are teaching them that good things happen in each other’s presence.

After two to three weeks of feeding exercises with no aggression, you can start allowing the cats direct access to each other with your supervision. Keep each room of the house equipped with special toys and treats, so the cats are distracted while in each other’s presence. Staring at each other leads to altercations in cat world, so try to keep their brains and bodies occupied with wand toys and treats when together. 

If the cats show warning signs of aggression, redirect their attention toward the enrichment, and take note of when and why the behavior occurred. Keep in mind that hissing is not aggressive behavior. Hissing is simply a cat’s way of communicating that they're not comfortable right now.

Consider synthetic feline pheromones as an aid

Cats have glands in their cheeks that produce pheromones, chemical substances that can help to relieve anxiety and that provide information about the cat producing those pheromones. When your cat rubs their cheeks against a wall, chair, or your leg, pheromones are left behind. 

Some cats respond very well to the use of a synthetic pheromone spray or diffuser — products that you can buy in pet supply stores. Because of its calming effect, this product is sometimes effective in helping to reduce aggressive events. (The spray is used in locations where cats rub, such as the edge of a couch. The diffuser is plugged into the wall and lasts a month.)

If these techniques do not solve your cats’ issues, please seek the help of a veterinarian and/or a behaviorist. Try to be patient. And remember, cats feed off of our emotions, so the calmer we are around them the better. In most cases, providing them with adequate playtime and social interaction and learning how to head off aggressive incidents will resolve the problem.