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  • Writer's pictureZia Mowbray

Tips to Stop Cat-on-Cat Aggression

Anyone who has lived, or spent much time, with cats will know they aren’t nearly as social as dogs. They do have very complex and selective social structures, however, especially in multiple cat households. As Emma Stenhouse wrote for Catster:

“Cats in a multi-cat household will often adapt to live together in a relatively small area and can sometimes form strong affiliative relationships among some of them. This is usually easier to achieve if the cats are all neutered or spayed. Some cats prefer the company of a particular cat and will display social behaviour with them that you may not see when interacting with another cat.”

This is because, just like humans, cats have multifaceted personalities, likes and dislikes, and tolerances for others. Some cats will be more willing to bond with other cats, whereas others will be more comfortable alone. Desexing, especially males, will always make cats calmer and friendlier to their own species, giving you a better chance at having two cats that like, or tolerate, each other. 

If you are finding signs of aggression between your cats, such as ears flattened backward on the head, tail held erect with hairs raised, back arched and hissing and/or swiping, it is very important to act fast to make sure they both are comfortable.

If your cats suddenly start fighting when they previously lived together without altercations, the first step is to take them both 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 behaviour. If a medical evaluation reveals no abnormalities, try out the tips below to help your cats to resolve their differences. 

(Note: These recommendations will also be helpful for cats that have been introduced to each other recently and are not getting along!)

Cat hissing due to unresolved aggression

  • Separation

The first step is to separate the cats from each other completely in separate areas of the house.

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.

Provide each cat with food, water, a litter tray, a comfortable place to sleep and regular interaction with you including playing and petting, this will ensure they feel safe and loved.

It is very important to ensure you are providing each cat with enough exercise and playful interaction. Fights often occur when one cat wants to play and the other cat doesn’t, so adjusting your routine to benefit both cats, in this case by providing the playful cat with more exercise, can eliminate the problem.

  • Recognising the “triggers”

Think about the “triggers” that might be causing the fights. For example, your cats may fight when both want attention from you, or when they both want the same resting place, or when they see another cat outdoors. When you can work out the triggers you will be able to develop a management plan to minimise them and bring your cats back together!

Some management plans may include:

Giving them options

If the cats primarily fight over resources, such as access to food or resting places, provide them with several options and spread them out so they can have their own “territory”. A cat will find it much more difficult to guard four food bowls than one.  

Reducing visual triggers

If the cats attack each other after seeing another animal outdoors, block visual access to the outdoors.  

Replacing bad habits with good ones

If the cats are fighting over access to and attention from you, you can teach them that this behaviour is not rewarding and that it drives away your attention instead. Pay 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, 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 and they will fight despite the fact that you are no longer in the room.

You can also teach the cats to come when called to help this strategy. When you see signs of anxiety you can call them to you and reward them for their good behaviour, shifting their focus. 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. 

If you don’t know how to teach a cat to come, it 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 favourite toy. Practise several times per day. You are teaching your cat that when you give the cue “come,” they are always rewarded. They’ll learn that it is much more worthwhile to come to you than to fight with the other cat. Make sure that you always reward your cat when you call them and they successfully come to you.

A cat playing with its owner, happy and calm

  • Reintroducing the cats

After you have decided what technique to use to prevent aggressive incidents you can 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 a metre and a half 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 further 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 cat’s direct access to each other with your supervision. Keep each room of the house equipped with special toys and treats. If the cats show warning signs of aggression distract them and redirect their attention toward you. Take note of when and why the behaviour occurred, and remember that mild aggressive displays such as hissing and then walking away can be normal when two cats have not seen each other for several weeks. Aggression is a form of communication and is not necessarily bad as long as the cats are simply listening to each other’s communication and are not fighting with each other.

  • Using pheromones as an aid

Cats have glands in their cheeks that produce pheromones, which are chemical substances that can help to relieve anxiety and that provide information about the cat producing those pheromones. When your cat rubs his or her 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, like the edge of a couch. The diffuser is plugged into the wall and lasts a month. Calming treats and/or catnip might also help alleviate any tension your cats are experiencing.

If the cats’ aggression doesn’t decrease after these strategies, and/or one or both the cats are at risk of harm, separate them immediately and consider your next options for keeping them apart. There’s a chance one or both of them needs to be the only cat in a home, and, unfortunately, won’t feel safe until this is the case. If you find yourself in this situation, you might have to consider rehoming one of the cats, as much as you don’t want that.


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