Non-recognition Aggression In Cats

Non-recognition Aggression In Cats

It is common for cats to indulge in rough play from time to time. However,  it is a different situation entirely if they actually become aggressive toward one another. If you notice your cats suddenly growling and fighting each other, you need to assess the situation. Such behavior may be attributed to something called non-recognition aggression. 

What is non-recognition aggression in cats?

This type of aggression occurs when one cat does not recognize the other despite them being friends or from the same household. Cats rely heavily on their sense of smell, and each group of cats has a so-called ‘group scent’. If one cat leaves the home for any reason, he is likely to be attacked upon his return because he smells different, as if he is from another group.  The attacked cat becomes frightened and attacks back, to defend himself. This happens even among lifelong feline friends. 

How does non-recognition aggression happen in cats?

Non-recognition aggression in cats most often happens when one of the cats visits the vet. When that cat returns from the vet, the other cats in the household will not completely recognize him, because he smells like a stranger. To defend themselves from this stranger, they will attack him. This aggression can also occur when one cat visits another home. Upon his return, he is attacked by the other cats in his household because he smells different. 

How can I prevent non-recognition aggression between my cats?

If you take one of your cats to the vet, keep him separated from the other cats in your household for at least a few hours when he gets home. During this time, he will be able to shake off some of the smell of the place he visited and will start smelling like home again. If the returning cat is feeling sick, separate him until he is well. Felines also smell different when they are sick.

When you reunite the cats, monitor them closely and prepare a large towel to separate them should they start fighting. If the cats are staring at each other, lashing their tails or looking tense, separate them rather than waiting until full-blown aggression occurs. Do not show anger or fear, and do not punish the cats. 

What happens if they attack each other?

If the cats attack each other, they need to be separated and should be reintroduced gradually. Undoing a bad introduction can be a lengthy process, so you will have to be patient and determined at the same time. Eventually, the cats will become used to each other and will stop fighting, provided they were reintroduced properly. 

Do not allow the cats to fight it out. Interrupt the fight by clapping your hands loudly or squirting the aggressive cat with a water gun. You can also direct compressed air at the aggressive cat.  

Types of feline aggression 

1. Play aggression 

Young kittens or cats that lack opportunities to play or are not raised with littermates are more prone to play aggression. Part of a cat’s socialization should be to learn the right way to play. Cats learn that they are hurting their littermates when the latter stop playing or retaliate. 

Cats that engage in play aggression will have their ears pinned to the tip of their heads, their pupils will be dilated, and they will thrash their tails back and forth. They usually stalk their target, be it a fellow cat or a person, and pounce from a hiding place when the target passes by. 

2. Fear aggression 

Cats usually manifest this type of aggression when they encounter an unfamiliar person, animal or noise. They could also associate the encounter with unpleasant events, such as vet visits. Felines in this situation tend to flatten their ears, bare their teeth, hiss or crouch, and their fur may stand on end. 

3. Petting-induced aggression 

Some cats become aggressive when petted, and this happens because they are overstimulated. Handling, grooming and bathing can also cause petting-induced aggression. 

4. Redirected aggression

If a cat is aggravated by a stimulus to which it cannot  directly respond, it will redirect the aggression to another person or cat. Stimuli that trigger redirected aggression could include altercations with other cats, loud noises, or seeing an outdoor or stray cat through the window. Aggression may be redirected to a person after an aggressive interaction with other indoor cats. 

5. Pain-induced aggression 

Cats that are experiencing pain tend to become aggressive toward people or other pets. Arthritic cats can be aggressive if their joints are manipulated or touched, and they may hiss, bite or scratch. Some cats may still be aggressive even after healing, in an attempt to avoid the pain they experienced before. 

6. Status-induced aggression 

Cats may assert social dominance by being aggressive toward people or other pets. They tend to block doors with their bodies or swat at fellow cats. 

7. Territorial aggression 

Cats can show aggression to establish and defend their territories. They may be aggressive toward newly introduced cats or people, and other animals within their territories. They may swat at, chase or attack encroaching animals or people. 

8. Maternal aggression 

Mother cats that have just given birth tend to become aggressive toward people and other animals that come too close to their kittens. Cat owners should provide an isolated area for mother cats, and avoid contact with the cat and her litter while she settles with them. This type of aggression will subside once the kittens are older.

9. Inter-cat aggression 

Male cats tend to have altercations with other males once they mature at around one to two years old. Female cats can also manifest this type of aggression. To address this behavior, neuter or spay your cats, because their sexual hormones play a role in inter-cat aggression. Reintroduction may also be done to address the issue. 


Cats may exhibit aggression toward fellow cats for a number of reasons. One of these is non-recognition aggression, which occurs when one cat has been separated from another and his scent is not recognized upon reintroduction. To address this issue, separate the returning cat for a few hours to allow him to get rid of any unfamiliar scents he may have picked up while away.  The two cats can then be gradually reintroduced. 

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