Feline Aggression Towards Other Cats in the Same Household

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, or play. Often aggression problems in multi-cat households will relate to a combination of these causes, so that accurate and comprehensive history taking is an essential part of reaching a diagnosis.

It is now widely accepted that, in situations of aggression between cats in the same household, aggression can be manifested not only in active aggressive behaviour but also in a more passive manner through strategic use of marking behaviours such as indoor urine spraying. Passive aggression is therefore a differential diagnosis in cases of indoor marking.

Redirected aggression is also common, especially when aggressive display 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 fine when it is directed at inanimate objects. However, other cats in the household are just as likely to become mock-predatory targets as their human counterparts.

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.

Diagnosis

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 domestic territory.

Some basic information is vital.

• A plan drawing of the home and garden indicating the location of feeding places, latrines, resting places and any other resources the cats make use of. This drawing should also include information about places that each cat prefers to use (resting places etc) and any locations of spray marks or inappropriate elimination.
• 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. It is often found that small factions or cliques exist within the whole group, with some cats remaining peripheral to the social group. There may also be ‘super-social’ individuals who show affiliative behaviour towards and are accepted by members of all of the factions. These cats may be instrumental in preventing outbreaks of aggression between factions.
• Observation of passive aggressive behaviours between the cats, chasing, resource guarding and other similar behaviours that indicate social conflict between factions or group members.

Common Causes

• 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)

Prevention

It is advisable to prevent the aggression towards other cats in the household by providing adequate resources so that competition does not develop. Several feeding, drinking and latrine sites distributed around the home to enable cats to have a real choice of location for these activities. Latrines may also be created in the garden. The local cat population density and whether it can cope with the addition of another cat needs to considered before attempting to introduce one. Choosing cats that come from successful multi-cat households or that have sociable parents as well as introducing them correctly is more likely to result in a successful outcome. Providing plenty of opportunities for appropriate play is also important.

Treatment

The ultimate aim of treatment is to produce a fully functioning cat group in which there is maximal affiliative behaviour and minimal aggression. Treatment of aggression within cat groups should only proceed where there is a genuine likelihood that the environment can be permanently modified to meet the cats’ needs. This may mean giving the cats access to more space, a larger number and diversity of resources, and possibly indoor-outdoor access if the cats are currently kept inside. Part of the solution to some inter-cat aggression problems may be to identify and re-home despotic cats, or to sensitively reduce the overall cat population in a household by re-homing certain factions en-mass. In this case the resolution is to produce several functioning cat groups that live separately. Some owners are fortunate enough to be able to provide two or more separate ‘homes’ for their cats within their property, using outbuildings. Making this kind of decision requires an in-depth analysis and understanding of the social dynamics of the group and how it accesses resources. A good solution that improves the welfare of all the cats should never be regarded as a failure, even if the cats are unable to continue living with the owner.

The cats responsible for initiating the aggression must be identified. It may be possible to fit the aggressor(s) with a bell and collar so that other cats can evade them faster.

The first step to treating inter-cat aggression is therefore to reduce apparent competition. Providing each cat-faction within a household with its own collection of resources will immediately reduce stress. The cats no longer have to queue for access to resources in close proximity to cats from opposing factions. Reduced contact in competitive situations will allow the cats to live in greater isolation from each other, but this in fact also enables them to associate with each other without the complication of competition for food or space.

In order to maximise available space for the cats it is also important to make the best use of the outdoor environment. Provision of extra resting places, perches and latrines outside will reduce competition for indoor resources. Access to outbuildings increases indoor space available to the cats, as does providing sheltered perches. Some owners are reluctant to give cats access to outdoors, and 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.

Part of reducing competition is to reduce the value of the owner as a ‘virtual resource’. The 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. Free access to food in bowls or activity feeders that always contain some food and are merely topped up by the owner at random will enable the cats to maintain distance from one another. Likewise cat-doors (preferably more than one) are better than a ‘human operated’ back-door.

Increasing access to space is also critical. The cat’s primary means of controlling its interaction with other cats is to maintain distance from them. In the small rooms that are typical of most homes, it may be very difficult for a cat to feel safe because it is always forced into closer than desirable proximity to other cats. This tends to favour aggression, because escape and avoidance are not possible. Fortunately, cats are able to make greater use of 3-dimensional space than humans and dogs, so giving them high perches in the form of shelves or cat furniture will enable the cats to re-engage avoidance and distance-maintaining behaviours.

Cardboard boxes and other low-down boltholes provide an excellent escape route for cats that are regularly chased aggressively or during play. This enables the victim to take refuge without having to run too far, and removes some of the reinforcement for chasing by the other cat. If the motivation for chasing is predatory play, then the owner should provide other play opportunities as an outlet for this motivation, such as play with a fishing toy and a changing supply of small, easily moved, brightly coloured toys.

The pheromone environment of functioning cat groups is quite special. Repeated face and flank marking of objects in the central section of the cats’ territory, combined with allorubbing and allogrooming creates a strong sense of security and identity. This can be lost when factions of cats or individuals dissociate from one another. This is commonest when people are not present to transfer odours between cats, or when a super-social individual within the group has gone. It can also occur when a house is redecorated, stripping odour marks from the environment, or when individuals 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 and flank 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. The pheromone F4 is very useful for preventing fear related aggression to previously unfamiliar individuals, but unfortunately, it is not suitable for treatment of inter-cat aggression within the household. F4 signals indicate familiarity, but with cats that have already had a number of aggressive encounters there may be a dissonance between the memory of the visual appearance of the aggressor cat and the chemical ‘familiarity’ signal. This has been seen to trigger apparent panic and violent outbursts.

A conditioned punisher such as a rattle may be used to disrupt aggressive behaviour at its outset e.g. to terminate threatening eye contact. When such an approach is used it must not be readily connected to the owner and should not be used in such a way as to actually frighten either of the cats. The aim is merely to startle the cats in order to disrupt the behavioural sequence but when used too late in the sequence, when the cats show great body tension and are preparing to strike, it may actually trigger an aggressive attack. It has to be remembered that fear and anxiety are driving forces for aggressive behaviour and anything that increases tension will probably favour fighting. Use of punishment is therefore not generally recommended. A better method of distracting the cats is to try to trigger a predatory behaviour that is directed at a toy. Most toys will not provide sufficient distraction, but laser pointer may be used carefully to break the cats’ concentration and lure them away from each other into a game. The advantage of this particular toy is that several cats can be independently distracted by moving the dot to different locations.

Successful resolution of aggression is most likely if individuals recognise each other as part of the same group. This can be achieved by swapping odours between the cats and possibly by isolating factions or individuals so that a complete re-introduction is carried out, as if the cats were being brought into the house for the first time. This may be the most appropriate course if the cats are likely to inflict serious injury on each other, or where it is relatively easy for the owners to keep the cats apart in this way.

Prognosis

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.