Aggressive behaviour (a threat, challenge, or attack) may include scratching, biting, and visual (e.g., changes in posture, erect fur), vocal (e.g., growling, hissing) and scent-based signals (e.g., urine spraying).
If your cat is being aggressive towards your other cat, the first step is to work out why. When you identify the reason(s), you can take steps to address the issue(s).
Cats express aggressive behaviour for different reasons, and it may be normal or abnormal depending on the context. They may be stressed, fearful, territorial, in pain, or even just playing.
Reasons for aggressive behaviour
Five common reasons for aggressive behaviour include: fear aggression, male to male aggression, play aggression, redirected aggression, and territorial aggression.
Fear aggression
Cats expressing fear aggression will typically hiss, spit, growl, flatten their ears and show a low/crouched body posture. Pupil dilation and erect fur are common, and they may spray urine. They will initially try to run away but may display aggression if avoidance is not possible.
Male to male aggression
In male-to-male aggression, which may be active (threatening) or passive (blocking access), the cat flattens his ears, howls, hisses, erects his fur, and uses both teeth and claws to fight.
Play aggression
It can be difficult to recognise play aggression because stalking, chasing, lying in wait, pouncing, biting, and scratching can be normal play behaviours in cats. Some cats play more roughly than others and do not retract their claws when they swat.
Redirected aggression
Redirected aggression occurs when the original target of the aggression is not accessible and the cat now directs the aggression towards an unrelated target (e.g., another cat) that enters the area soon after the original trigger. For example, your cat may see an unfamiliar threatening cat outside the window who, because they can not get at the cat outside, if your other cat enters the room the aggression may be directed towards them instead
Territorial aggression
A cat may patrol and mark their territory, and act aggressively towards other cats that approach or enter their territory. Territorial aggression is more likely between unfamiliar cats and in entire males during the breeding season.
Treatment and prevention
Specific treatment and prevention strategies may depend on the reasons for aggression. General steps to reduce the risk of aggressive behaviour between cats include: preventing kittens being removed from their mothers too early, appropriate socialisation, desexing, and carefully planned introduction of unfamiliar cats. It is essential to provide adequate multiple and separated resources (e.g., litter trays, food bowls, toys, scratching posts, water, elevated platforms, sleeping areas etc.), and opportunities to express natural behaviours and engage in stimulating activities (enrichment). See the RSPCA Guide to Keeping Your Cat Safe at and Happy at Home for more information on providing an optimal environment for your cats. Synthetic pheromone diffusers may also be beneficial.
If the aggressive behaviour persists, seek veterinary advice. Aggressive behaviour may indicate pain and/or physical health problems so your vet can investigate these, and if they are ruled out, may recommend a management plan that could include measures such as environmental changes, behaviour modification and/or medication. In some cases, separating the cats may be necessary.
A cat expressing aggressive behaviour should not be punished or forcibly restrained as this can increase stress, inadvertently encourage the behaviour, lead to other problems, and make the situation worse.
