Feline Aggression Towards Other Cats in the Same Household

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Key Points

  • Individual acts of aggression between cats must be minimised.
  • Vantage points used by aggressive cats to observe access points and resources should be removed.
  • Provide each faction with its own complete set of resources and F3 diffuser, located in an area where the cats already spend most of their times.
  • Provide additional hiding and resting places around the house, including 3-dimensional space.
  • Provide low-level boltholes such as cardboard boxes so that cats have easy access to an escape route when chased.
  • Consider isolating factions or individuals if there is a significant risk of fighting or if previous attempts at re-introduction have failed.
  • Proceed with an odour introduction routine. Some deliberate odour swapping and the provision of additional resource locations may be needed to maintain permanent harmony.
  • It may be possible to inhibit aggressive behaviours at the moment that they start, using a conditioned punisher.
  • Increase play to reduce the incidence of predatory play directed at other cats.
  • Consider rehoming if successful environmental management cannot be maintained.

Aggression Between Cats in the Same Household

Aggression between cats in the household is motivated by the same underlying emotional responses as aggression towards people. These include fear, frustration, predatory behaviour, play and resource control. Often aggression problems in multi-cat households will relate to a combination of these causes, so accurate and comprehensive history taking is an essential part of reaching a diagnosis.

Redirected aggression is also common, especially when aggressive displays towards cats outside the house is thwarted, and the cat turns its attention to an easier target within the house, such as another cat.

Feline play often involves rehearsal of predatory behaviour, which is acceptable when directed at inanimate objects. However, other cats in the household can become mock-predatory targets for this type of play in the same ways as people.

Inter-cat aggression within the household is most likely to occur at certain key times, such as when a new cat is being introduced to the household. This may be due to fear of the new cat or due to more general effects on the availability of resources such as resting places, owner attention or food. Another important high-risk event is when a cat that has been temporarily hospitalised or housed in a cattery returns home. Poor socialisation of one or more of the cats in the home and the presence of social stress within the household are also factors that need to be considered.

Prevalence and risk factors

There is no reliable prevalence data for the specific problem of inter-cat aggression within the household, but problems such as indoor spray marking and elimination, and scratching are common and associated with inter-cat conflict. As with other problems, overpopulation and under-provision of resources are likely risk factors.


Common underlying factors include:

  • Illness or debilitation
  • Social pressure due to excessive population density
  • Inappropriate introduction procedure with a new cat
  • Temporary isolation of individual cats leading to failed recognition when they return, or loss of group odour
  • Fear-related aggression
  • Predatory or play-related behaviour
  • Redirected aggression (frustration)

As with house-soiling and spraying problems, it is important to fully understand the nature of the cat’s relationships with each other and the way that they make use of their territory in and around the home.

Several types of information are required for an investigation:

  • The personality, experience and health state of individual cats.
  • Interactions between cats within the household.
  • The physical environment available to the cats (inside and outside the home).
  • The population of cats in the neighbourhood (as a potential source of stress and conflict).

Individual cats:

  • Behaviour and origin of parents, if known.
  • Rearing conditions and experience during the sensitive period.
  • Past history of living in multi-cat households (especially if rehomed).
  • Process of introduction to the household (including age of the cats during introduction).
  • Interaction with the other resident cats, prior to current problem.
  • Medical history and physical examination.

Interactions between the cats in the household:

  • The relationship between the cats can be determined by looking at the pattern of allorubbing, allogrooming and other affiliative behaviours such as tail-up greetings between individual cats.
  • This can be recorded on a diagram indicating the type and direction of communication between individual cats.
  • Observation of aggressive behaviours between the cats including chasing, resource guarding and other similar behaviours that indicate social conflict between factions or group members.

Physical environment:

  • Assessment of the amount and distribution of resources.
  • Availability of key resources (such as access to food).
  • Opportunities to perform normal behaviour (including play and rest).
  • Opportunities to perform avoidance and escape behaviour (to maintain distance from conflicting cats).

Neighbourhood cats:

  • Signs that non-resident cats may have entered the home to steal food or conflict with resident cats.
  • Evidence of local overpopulation, conflict with non-resident cats or the presence of intact male strays.


Treatment of inter-cat aggression problems includes interventions that operate at a group level as well as an individual level.

Treatment should take into account:

  • Individual personality and behaviour.
  • The relationships between the cats.
  • The physical environment and resources.
  • Conflict and competition with neighbourhood cats.
  • The relationship with the owner.

The Individual:

Not all cats place the same value on specific resources, and the environment may need to be altered to take this into account. For example, providing more feeding locations if a timid cat is finding it hard to access resources. The coping strategy of individual cats also varies. In the past, clients have been advised to provide climbing and high resting places for cats, but nervous cats appear to prefer floor level hiding places. Households may include individuals with very different levels of sociability and boldness, and the provision of play and resources should take this into account. For example, environmental enrichment with activity feeding may be of interest to only one cat in a household, that is not the main antagonist in inter-cat aggression, but by satisfying this cat's behavioural needs the group social dynamic is improved. In some cases individual cats show such high levels of anxiety and inhibition that they are unable to access resources or become the target for predatory play or bullying. These cats may benefit form psychoactive medication to reduce anxiety. In other situations, an individual cat may behave despotically, controlling access to resources so that other cats are unable to use them. This can be the result of a medical condition, such as hyperthyroidism or diabetes mellitus, which increases the value of food resources. It can also be a feature of the personality of some cats. Hybrid cats may be particularly problematic in multi-cat households, as their social and territorial behaviour may not be compatible with domestic cats. In some cases, individuals may need to be rehomed in order to improve the welfare of the remaining cats.

Relationship Between Cats in the Household:

The basis for recognition in cats is group odour. This is created and maintained by allorubbing and allogrooming, which transfers and mixes scent between members of a group. When cats leave facial and flank marks they will deposit this group odour in the environment. Once a problem has become established, there may be little or no scent transfer between individuals or factions of cats within a household, so there may be no common group odour. These individuals and factions need to be given their own resources, so that there is less competition between them. In some cases a group odour did exist, but it is lost when people are not present to transfer odours between cats, or when a super-social individual within the cat group has gone. It can also occur when cats are reunited after a period of separation (such as when hospitalised or having gone missing). The use of F3 diffusers can simulate the effect of dense facial marking within an environment, whilst the cats re-establish their own marks and exchange odours that identify them. F3 diffusers may be removed when the cats are freely associating without aggression and showing allogrooming and allorubbing between members of factions. A group odour can be deliberately created by the owner, by collecting and transferring scent between cats, in the same way as when introducing a new cat to the household. In fact, in some cases, it is recommended that cats be separated completely for several weeks, before being reintroduced as if bringing in a new cat. Synthetic F4 pheromone may also be helpful in this situation as it has been described to manage intercat conflict.

Physical Environment:

Cats form social groups on areas where resources are in excess. These groups break up and suffer conflict when resources are insufficient. In a domestic setting cats gain such high quality shelter and food that they will remain resident when social conflict in any other situation would have forced them to leave. In addition, in urban areas outside population density may be high, and resources so apparently scarce, that resident cats have little choice but to remain where they are. Improving access to resources is key to reducing conflict and competition. This includes giving the cats multiple feeding sites, latrines and plenty of choice or resting, climbing and hiding places. Access to outdoor space through a secure cat flap reduces pressure on space within the home, and permits cats to engage in normal hunting and territory behaviours that are highly motivated. However, in some countries cats are not permitted to roam free. In these cases, a secure outdoor run may be a viable option, to increase available space. If factions or isolated individuals have been identified within the group, these should be specifically provided with dedicated resources that are are apart from other cats. By doing this, conflict is reduced and it is more likely that the cats can be formed into a single social group.

Neighbourhood Cats:

Pressure on resources within he home will be increased if resident cats do not feel secure to leave the home and utilise their territory. The outdoor environment should therefore be altered to enable resident cats to properly control the garden as territory. This includes providing places for resident cats to claw and urine mark, outdoor places for them to perch, shelter and eliminate, and a garden that is planted to encourage wildlife and to provide cover for the resident cats to move around. Neighbourhood cats should not be fed or encouraged to enter the garden. Intact stray cats should be trapped and neutered.

Relationship with the Owner:

Part of reducing competition may be to reduce the value of the owner as a ‘virtual resource’. Resident cats may regard the owner as a source of food, as well as security. They may be unable to gain access to food or go in and out of the house safely when the owner is not present to protect them. This also means that cats tend to congregate around the owner, which places them in close proximity at a time when they are most desperate to get food or outdoor access. Owners may try to establish a "pecking order" between cats, based on the idea that some cats are dominant in the group. It is best for all resources the cats need to be freely available, and not on demand form the owner. This reduces dependence and tension between cats at feeding times and when the owner is around.

Owners should not physically intervene when cats are showing aggression; shouting, touching or trying to pick up a cat during a fight is likely to lead to redirection and serious injury to the person. If owners want to intervene to stop fights, they should use distraction rather than physical intervention or punishment. For example, using a fishing toy to distract the cats at the first sign of tension between them. This method is affective if the owner acts quickly at the start of aggression, but will not work once cats are in a stand-off.


The prognosis for these cases depends upon several factors, including owner compliance with environmental modifications, the ability of the home environment to support the intended cat population, sociability of individuals within the group and the owner’s expectation of the end result. Continued maintenance of the conditions that enable the group to coexist is paramount.

Cats are able to coexist successfully in groups but it is essential to prevent problems by choosing cats that are likely to be sociable and then introducing them in the right way. Rehoming some cats may be essential to provide the whole group with better welfare.

In households where there is a problem of overpopulation or a clash in personality between individuals it should not be regarded as a failure if the ultimate recommendation is to rehome certain cats.


Inter-cat aggression can be prevented by:

  • Providing free access to an appropriate amount of resources that are distributed to allow all cats easy access.
  • Proper introduction of new cats to the home.
  • Avoiding overpopulation both in the home and in the local area.
  • Avoiding introduction of adult cats that are nervous or do not have a history of living in a multi-cat household.

It is common for a cat to lose group odour and pick up unfamiliar scents after a period at the veterinary clinic (for example, during dental work or neutering). These cats may not be recognised when they return to the home in a groggy condition after partial anaesthetic recovery, smelling different and behaving oddly. It is best to allow returning cats several hours in isolation to fully recover, clean themselves and pick up scent from commonly used bedding. Installing an F3 diffuser may also be beneficial before bringing the cat back home.

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