Aggression between Housemate cats

There are a number of factors which may cause aggression to develop in previously happy relationships between housemate cats.


This seems to upset the balance between cats in a household fairly frequently. This may be to do with a need to establish new individual territories within the new home or may simply be just insecurity and stress.

Change of boundaries

Cats who are indoor/outdoor cats have a stronger tendency to have territorial aggression than cats that stay indoors. Again, this may have to do with territorial pressures, such as urine marking, which they encounter outdoors. When cats who were previously ’indoor’ only are allowed to become indoor/outdoor cats there is sometimes a marked increase in territorial aggression.

A new face

When a cat feels challenged by an outsider, there is often an increase in aggression towards housemates.


Sometimes male cats just seem to grow into aggressive behaviour. In dogs this seems to be an age related effect that has to do with social status but it is not clear whether this is the case with cats. It does however seem to be true that some male cats become more and more aggressive and territorial as they get older.

Veterinary Treatment

No one knows why cats that were living together peacefully find reasons to dislike each other after one of them leaves the house for treatment at the vet’s but this is not an uncommon problem. In most cases, the cats will eventually re-establish their normal relationship but in some cases they need help.

In the case of all housemate cat aggression, sometimes just keeping the cats in separate rooms for a few days and switching them back and forth between rooms will allow them to get used to the idea that they have to live with each other again. The product Feliway (TM), which is a synthetic phermone that is calming to cats can sometimes help cats make the transition back to normal relationships. Feliway isn’t made to be sprayed on pets directly — spraying it around the room at strategic spots like the corners of furniture helps to produce an environment that encourages calmness among the cats. Feliway is also available as a room diffuser which treats a large area without the need to re-spray. Your veterinarian can order Feliway for you if you want to try it.

Aggression in Kittens

Often aggression in kittens is attributable to play aggression (not that this makes it any less upsetting and or painful when your kitten attacks you!)

Play behaviour starts early in kittens and is normally directed towards their littermates and/or parents. Both their littermates and parents are not averse to responding to overly aggressive behaviour by equally aggressive behaviour – if bitten too hard they may bite back. In addition, they often suspend play activities with the overly aggressive playmate, which is another form of punishment that works. After all, the whole object for the over-enthusiastic kitten is to play.

Play behaviour often involves hunting and pouncing , so “surprise attacks” are common. The kitten is exhibiting a natural tendency to learn to hunt, since hunting success has a lot to do with survival. Play attacks are often sudden and most commonly involve both scratching and biting which ceases just as quickly as it began. Kittens that get excited quickly may react to something as simple as an attempt to pet them with an aggressive attack on the hand that is approaching them.

Most kittens find a few places in the house that are good for ambushing and use them over and over – but some vary their routine quite a bit. Learning to anticipate an attack is very helpful. The kitten learns best if the play behaviour can be stopped while it is in the “thought” process rather than the “action” process. Something that will reliably distract the kitten from the attack works best to stop them.

How to distract a kitten

A whistle, clap of the hands or stomping of the foot may be sufficient to stop the attack if it is recognized in the formulative stage. It may be necessary to use an air horn or to shake a can with a few pennies in it to produce enough stimulus to stop an attack that is in progress. If you use an air horn, sound it as quickly as you can during the attack – the idea is to avert the attack if possible and to punish the behaviour while it is in progress, if you can’t avert it.

For some kittens a water gun will work as well as an air horn but some just look at this as more intense play. Once you have averted an attack, move to another room and avoid playing with the kitten until it calms down. Remember that it wants to play and will learn to play more appropriately if you encourage good behaviour and discourage inappropriate ones.

Don’t give the kitten mixed messages – avoid playing rough, especially with your hands. Don’t encourage the kitten to attack the drawstring of your sweatshirt or your shoelaces. When you do play with the kitten try to play with a toy that gives the kitten exercise. A toy tied to a wand or on a line you can throw out and retrieve can be helpful. Don’t reel the kitten right to you with the toy — stop the action at a safe distance to prevent the kitten from getting the idea of continuing the play by attacking you. If it is possible to use a lot of the kitten’s energy in activities like this, the frequency and intensity of play attacks almost always lessens.

One Comment

  1. With ours it was definitely a case of them being territorial as they got older (male cat) as the article says, it was very strange and sudden.

    We tried everything and the vet recommended we give them something to mark their territory on that would be just for them.

    Scratching post seems to have done the trick since he’s a lot less aggressive with our hands now, thank god.

    There’s some good reading material on how they use them to mark their territory on this article which I wasn’t aware of beforehand:

    We never had the problem with scratching furniture though, just us!! Weird.

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