Cat-cat aggression within the household

Cat-cat aggression within the household

Pet Psychology

The domestic cat is becoming more and more popular but increasing densities of local cat populations are likely to lead to a rise in conflict between cats. The presence of other cats, either within the same household or within the same neighbourhood, which are not seen to be part of the same social group, can be a source of high levels of stress. The behavioural responses to this enforced company can be easily missed as it can be very subtle but overt aggression can also often result.

Understanding feline aggression

Aggression describes a range of behaviours, including threatening behaviour such as staring, hissing, spitting, scratching and biting. In most cases aggression is a normal, adaptive behaviour and will have developed through learning that such behaviour is necessary or effective at getting what the cats wants - in most cases for a threatening individual to back off. It is therefore normal for cats to show aggression if they feel threatened and are unable to escape from the perceived threat.

Why do cats fight?

Cats are innately threatened by others that are not seen to be part of their social group. Although the domestic cat evolved from the African wildcat, a largely solitary and territorial species, it has evolved the ability to live in social groups, but only in specific circumstances. Naturally occurring groups of cats, such as feral or farm colonies, are very friendly, where individuals frequently rub and groom each other. Rubbing creates a group scent profile, allowing cats to recognise members of their social group. Yet despite their friendliness, cats still hunt and eat alone. Additionally, the size of the group fluctuates with the availability of resources. This means there is very little conflict over resources and therefore little reason for aggression to arise. However, if a cat from outside the social group tries to hunt on their territory, colony members will use aggression to rid the group of the threat to food and other resources. In the domestic situation, although usually well fed by owners, cats remain highly motivated to protect their territory from cats that are not part of the social group and this can include cats that live in the same household. If two cats have not grown up together from a young age there is a high risk that they will not accept each other as part of the same social group and will therefore feel threatened by the other’s presence.Unlike dogs and people, cats find it very difficult to resolve conflict as they have limited social communication skills. African wildcats are rarely in close proximity to each other; therefore, they did not need to develop a complex visual signalling system. This inability to show a range of visual signals has been maintained throughout domestication. This means that domestic cats cannot easily read each others’ emotional states or deal with situations of conflict. Consequently, where cats cannot easily avoid other cats, for example when two household cats have to share a cat flap, they may become stressed relatively often and start to fight.Low tolerance of other cats may also result from a lack of socialisation during the early developmental period. The socialisation period occurs between about 2 and 7 weeks of age, during which kittens learn about all the sights, sounds and experiences that form a part of normal life. Whatever social encounters a kitten experiences during this period will therefore influence social behaviour later in life. There is also a strong genetic influence on a cat’s behaviour, including its social behaviour, which will influence the cat’s emotional response to other cats.Aggression can also occur for a number of other reasons, such as frustration or re-directed aggression or because of internal changes. Therefore, a medical examination is essential prior to behavioural consultations to ensure that any behavioural changes are a result of environmental factors rather than physiological ones.


Due to the innate nature of cat-cat aggression, treatment relies more on environmental management than behavioural modification. Successfully identifying the different social groups in the household, by noting which cats rub and groom each other, will allow the provision of all the cats’ necessary resources in separate areas of the house. These areas must be carefully considered as the cats must have free access to resources at all times, i.e. without having to walk past another cat not seen to be in the same social group.


Think very carefully about getting a cat if there are already several cats in your neighbourhood, or before adding an additional cat to your household. Who will actually benefit from an additional cat? Your existing cat almost certainly will not. However, if you want a second companion for yourself you must be very careful when introducing unfamiliar cats in order to encourage a positive relationship between the two. House your new cat in his own room, with all the necessary resources. Keep him in there for several days, allowing him to settle into his new environment. This also gives you the chance to introduce the scent of each cat to the other before they come face to face - this is essential as scent is the most important aspect of group recognition in cats. Start by swapping the cats’ food bowls, bedding and toys. Then alternately stroke each cat without washing your hands to simulate the action of the two cats rubbing against each other and transferring their individual scents to produce a group scent profile. Once the cats are fully relaxed with the introduction of each other’s scent they can be introduced visually. This should initially be at a distance, perhaps with each cat at opposite ends of a large room, ensuring each cat can easily escape if feeling threatened. Gradually increase the duration of visual contact between the cats until they no longer need to be separated and ensure that the cats are always in a positive emotional state by playing with them or giving them a fuss. Do not feed them together in the same room as eating in close proximity to other cats, even friends, can be stressful and may lead to digestion problems. By slowly introducing the cats they will hopefully accept each other as part of the same social group and therefore not feel threatened by the other’s presence. However, you should still be cautious and provide each cat with his own core area, complete with all the necessary resources to avoid any situations of conflict.

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