When The Fur Flies: Why Your Cats Are Suddenly Fighting

If you have more than one cat and they all get on well, you’ve pretty much hit the jackpot in pet parenting terms. Many longtime cat parents will have had cats who don’t get on, and having them stay out of each other’s way is the best scenario.

But what about when your cats previously did get on – whether they’re a bonded pair who were best friends, or they simply coexisted calmly in the same house – but have suddenly started fighting? 

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We’ve spoken to some of the pros to find out what we can do to support our cats – and when it might be time to reach out for external help.

Why do cats suddenly start fighting?

“One of the most common reasons for cats who have previously gotten along well to suddenly start fighting is stress from an environmental change,” says Sammie Ravenscroft, Cats Protection regional community behaviourist. “This could be the introduction of a new pet or baby, visitors coming to the home or changes in the cat’s general routine.”

Sometimes, cats fight because there’s competition for resources or heightened feelings of stress or boredom. Redirection is another possible cause. This is when a cat acts aggressively towards another cat or someone else they usually get on well with because they’re frustrated by another stimulus they can’t interact with – like a rival cat the other side of the window. 

Non-recognition aggression can be another cause, and this can occur even with cats who have been bonded for life. It can happen when one cat returns from somewhere else – often the vet – with unfamiliar scents. “Cats are very sensitive to smell and they love predictability and routine, so these changes can have a big impact on the relationship between cats in the home,” says Ravenscroft. 

If your cats have spent some time away from each other, you might actually need to reintroduce them. Their scent profile may have changed, meaning they might not recognise each other. You can do so in the same way as you’d introduce a new cat to the household to the cat you had first. 

Sometimes, it can be down to a medical issue like a sudden illness or pain. When a cat isn’t feeling well, they might be less tolerant of other cats – and even humans – and more irritable. It could be anything from dental pain or arthritis to hyperthyroidism or an infection. Cognitive decline in senior cats and neurological issues like epilepsy and brain tumours can also lead to aggressive behaviours, so contact your vet if you’re concerned. 

How can you tell if it’s serious fighting?

“There’s no way to know 100 percent,” says cat behaviour consultant Tom Kirby. However, he points out that, according to studies, sound is the most reliable way to tell. If your cat is being vocal – whether hissing, growling or making other sounds, they likely don’t consider the fighting to be playful. 

Other indications of serious fighting are that the claws are out rather than staying retracted and that their fur might be puffed up, particularly around the tail area. 

Lucy Hoile, certified cat behaviourist, explains, “Play is very turn-based too, so if one cat chases and pounces on the other, you should notice they switch roles later on, whereas fighting is usually one-sided.” Cats that are fighting, however, are “tense with wide, dilated pupils”, says Hoile.

If your cats end their fighting session before you need to intervene, take a look to see how they’re behaving. After playfighting, cats usually go back to normal pretty quickly. When they’re actually fighting, it can take quite a while for them to resume normal behaviour. 

How to break up a cat fight safely

“Most people try to be rule enforcers with their cats, but that can result in more aggression as the cats become fearful of you,” says Kirby. “It’s much more beneficial if you take note of early signs of stress and calmly distract the cats before that stress turns into conflict.”

If you think your cats might end up fighting – maybe they’re staring at each other – he recommends walking over and sitting between them without looking or speaking at them, as if your decision to sit down is totally unrelated to them being present. “Once the cats are focused on you, offer both of them affection and non-competitive play on opposite sides of you,” he continues.

If the fight has already started and doesn’t seem to be finishing quickly on its own, he advises using the ‘Magic Towel’ method. This involves tossing a large, heavy towel over the cats, distracting them from the fight. If possible, try to avoid showing them that you’re the source of the towel – it needs to appear as if by magic. 

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“If you can only cover one cat, cover the aggressor so the other cat can leave the area without being chased,” Kirby adds. “You may have to hold the edges of the towel down around the aggressor to do so, but most cats will become compliant in this situation for a short time.”

Once you remove the towel, offer the aggressor some treats and play with them for a while. This means they’re less likely to run off and look for the other cat straight away, and also that they’re more likely to cope by seeking you for playtime rather than being aggressive towards the other cat. 

However, Kirby describes this method as a last resort that shouldn’t be used very often. It’s best not to intervene unless it’s necessary – we don’t have fur to protect ourselves, so we often come out worse than the cats when we get involved and try to pick up one to remove them. “The risk of the cat panicking and turning around to bite you is very high,” says Hoile, “And even if they are just trying to get free from your grip, you will undoubtedly be caught by their claws even if they aren’t trying to hurt you.”

Ways to prevent fighting

First and foremost, ensure that you’re providing your cats with plenty of resources. It’s good to give your cats choices so they feel like they have agency. If they don’t have their own essential items placed in separate locations of the home – such as food, water, litter trays, beds and scratching facilities – it can put strain on the relationship,” says Ravenscroft. “Cats are a solitary species by nature and like to have their own essential items, even if they are bonded to another cat.”

Ideally, you’ll have one of everything for each cat, as well as one extra. This way, you’ll both reduce competition but also allow your cats to be able to avoid each other if they’d like to. 

“Giving them plenty of high places to go will open the territory and help them keep out of each other's way to avoid fights,” adds Hoile. This is particularly important in places like hallways to avoid them facing each other head-on. 

Female cats in heat can act aggressively, as can young male cats, so this is another good reason to ensure your cats are spayed and neutered.

When to contact your vet

If your cats are living in a tense, high-stress environment, this can lead to health issues. Taking this into consideration, as well as the potential medical reasons for fighting, a vet visit is advisable to ensure both cats are in good health. 

Taking potential health issues out of the equation, however, your best bet is likely to speak to a cat behaviourist or behaviour consultant. They can spend time learning about the cats involved, your home and the situation, and then offer advice. 

Ideally, it’s best to be proactive and create the circumstances for multiple cats to live together peacefully right from the off. But this won’t totally minimise the risk of your cats fighting. If one suddenly develops an illness or injury, doesn’t recognise the other’s scent after a vet visit, or redirects their aggression, a cat fight could occur. 

In these instances, if you can’t prevent the fight before it starts and it shows no signs of dying on its own, you may need to try the ‘Magic Towel’ method. Above all, it’s best to visit your vet to rule out anything serious, and speak to a behaviourist if the fighting persists. 

And, while this might not be something you’d like to think about, Hoile advises, “If the cats are attacking on sight and there are any injuries or long-term stress, it may be kinder to find one of them a different home.”

Hopefully, of course, it won’t get to that point, and your cats will go back to being friends, or at least coexisting peacefully with each other.