The domestic cat has become an increasingly popular pet in many countries. Unfortunately, behavioural problems are common in cats and they may have a negative effect on the quality of the human-animal bond and on the cat's welfare. Aggressive behaviour towards humans or other cats is a relatively common complaint in feline behavioural medicine, being second only to inappropriate elimination.^1,2 Aggressive behaviour has a negative impact on the welfare of cats as it may lead to injuries, infections and pain. Also, aggressive behaviour elicits a stress response which is further detrimental to the welfare of the animal.

The high proportion of multicat households in many countries may contribute to the high incidence of inter-cat conflicts.³ By contrast, aggression towards the owners is more frequent in single-cat households.⁴

Additionally, the origin of each individual cat plays an important role since cats that have been obtained from a pet shop seem to be more likely to develop aggressive behaviour.⁵ This has been explained though a variety of mechanisms, lack of proper socialization being the most likely.⁶

The most common forms of aggressive behaviour towards other cats are fear aggression, territorial aggression and intra-sexual aggression. Fear and territorial aggression can be distinguished based on the cat's body posture (defensive in fear aggression and offensive in territorial aggression) and the time course of the problem, which tends to be more gradual in the case of territorial aggression and more sudden in fear aggression. Intra-sexual aggression is shown between adult, entire males.

Easy access of all cats to all important resources (i.e., feed, water, litter tray, scratching posts and resting and hiding places) is of paramount importance to decrease the risk of inter-cat conflict. In some forms of aggression (such as intra-sexual aggression), castration may be useful. Additionally, a reintroduction protocol should be applied if there are fights.^7,8 The protocol is divided into 3 phases: olfactory habituation, visual habituation and direct contact habituation. In the first phase, each cat is confined in a different part of the household and all important resources are provided in both areas. Each cat is then moved to the other area so that both animals are exposed to the other cat's odour. Additionally, the secretion of the facial gland of each cat can be applied to the cheeks of the other cat by using a piece of cloth. The visual habituation phase can start when both cats are relaxed during territory exchanges. In this phase, visual contact between cats through a mesh door, for instance, is provided when cats are engaged in a pleasant activity. Cats are otherwise kept separated and the duration of the visual contact sessions is gradually increased. Finally, in the last phase of the reintroduction protocol (direct contact habituation), the wire mesh is removed. The duration of each part is variable as it depends on the severity of the conflict, the cats' response and the owner's involvement.

Many cases of aggression towards humans are either petting-related aggression, inappropriate play or redirected aggression. Petting-related aggression occurs when a cat suddenly feels irritated by being petted, bites the person petting it and then jumps up and runs off. This behaviour may be very difficult to understand by owners as oftentimes cats will look for attention and almost immediately will react aggressively. Owners should learn the cat body language and for how long petting is tolerated. Counter-conditioning exercises may help to increase the cat's tolerance to being petted.

Inappropriate play is a behavioural problem that can be directed to people or to other cats. This behaviour seems to be more frequent in cats that have been weaned at an early age and spend long periods of time with limited opportunities to play. Typically, play behaviour in cats includes predatory movements such as stalking, chasing and biting. Punishment is not effective to eliminate this behaviour and may increase the risk of a defensive reaction towards the owners. The best way to correct the problem is to increase play opportunities through environmental enrichment and by eliciting appropriate episodes of play, for example by using small, moving objects.

Redirected aggression occurs when cats are unable to direct aggression towards the eliciting stimulus, which very often is the presence of another cat or a noise.⁹ Cats with redirected aggression may display very sudden, violent attacks. The attacks are usually difficult to stop, and cats with this form of aggression typically remain highly aroused long after the triggering stimulus has disappeared.⁹ This fact can make diagnosis difficult because the relationship between the aggressive episodes and the primary triggering stimulus may not be obvious. It is therefore very important to teach the owner how to identify subtle aggressive signals and deal with an aroused cat. In addition, if at all possible, the exposure to the triggering stimulus should be totally avoided.

It is important to emphasize that a medical check-up is needed in order to rule out organic diseases that could cause or contribute to the development of aggressive behaviour. In addition, in all cases of aggressive behaviour in cats, a risk assessment should be done to decide if treatment is safe. Risk assessment should take into account both the type and intensity of the aggressive behaviour and the characteristics of the affected individuals.

References

1.  Association of Pet Behaviour Counsellors. Annual review of cases 2005. http://www.apbc.org.uk/. 2005.

2.  Bamberger M, Houpt KA. Signalment factors, comorbidity, and trends in behaviour diagnoses in cats: 736 cases (1991–2001). J Am Vet Med Assoc. 2006;229:1602–1606.

3.  Amat M, Ruiz de la Torre JL, Fatjó J, Mariotti VM, Van Wijk S, Manteca X. Potential risk factors associated with feline behaviour problems. Appl Anim Behav Sci. 2009;121:134–139.

4.  Heidenberger E. Housing conditions and behavioural problems of indoor cats as assessed by their owners. Appl Anim Behav Sci. 1997;52:345–364.

5.  Crowell-Davis SL, Barry K, Wolfe R. Social behavior and aggressive problems of cats. Vet Clin North Am Small Anim Pract. 1997;27:549–568.

6.  Casey RA, Bradshaw JWS. The effects of additional socialization for kittens in a rescue centre on their behaviour and suitability as a pet. Appl Anim Behav Sci. 2008;114:196–205.

7.  Beaver BV. Fractious cat and feline aggression. J Feline Med Surg. 2004;6:13–18.

8.  Moesta A, Crowell-Davis S. Intercat aggression - general considerations, prevention and treatment. Tierarztl Prax Ausg K Kleintiere Heimtiere. 2011;2:97–104.

9.  Amat M, Manteca X, Ruiz de la Torre JL, Mariotti VM, Fatjó J. Evaluation of inciting causes, alternative targets, and risk factors associated with redirected aggression in cats. J Am Vet Med Assoc. 2008;233(4):586–589.