why do cats suddenly start fighting
By Anita Kelsey – UK cat behaviourist
why do cats suddenly start fighting? Well, there are many reasons why a cat may choose to fight another cat. In reality, most cats prefer to avoid physical conflict because fighting carries a high risk of injury. In many situations, one cat will attempt to defuse the confrontation by slowly backing away, avoiding direct eye contact, or using subtle body language to signal that it does not want trouble. If the other cat accepts these signals, the conflict is often avoided.
However, there are times when a cat feels it has no choice but to stand its ground. Cat-to-cat aggression can occur for several reasons. A cat may be defending its outdoor territory, most commonly its own garden, or protecting its home after an unfamiliar cat has wandered indoors. Conflict is also common in multi-cat households, where tensions can gradually build between cats that are not closely bonded.
Introducing a new cat into the home is another frequent trigger. While people often assume the resident cat will be the one to react aggressively, either cat may become fearful, defensive or aggressive depending on how secure they feel and how introductions are managed.
One of the most misunderstood forms of feline aggression is redirected aggression. This occurs when a cat becomes highly aroused after seeing another cat outside, often through a window or patio door. Unable to chase the intruder away, the cat’s frustration and emotional arousal can be redirected onto the nearest target, which is often another resident cat, but can sometimes be a person.
Cat aggression can cause serious injury, particularly when a bite breaks the skin. A cat’s teeth are long, narrow and extremely sharp, meaning they can create deep puncture wounds while leaving only a small opening on the surface. Bacteria from the cat’s mouth can therefore be pushed deep beneath the skin, where the wound may close over and trap the bacteria inside. This can lead to a painful and potentially serious infection.
Any cat bite that breaks the skin should be washed thoroughly with soap and running water as soon as possible. Medical advice should be sought promptly if the wound is deep, is on the hand, face or near a joint, or if there is increasing pain, redness, heat, swelling, discharge or fever. Cat bites can become infected quickly and may require antibiotics or further treatment.
It is natural for cats to defend their territory, but situations can quickly escalate when a neighbouring cat repeatedly ignores social boundaries and continues to intrude. This can lead to ongoing tension, fighting and, in some cases, disputes between neighbours. I have been asked to help mediate many of these situations, and they are far more common than people realise.
Whatever the cause of the aggression, it is important to address the circumstances promptly. Early intervention can help prevent the behaviour from becoming established and reduce the risk of long-term stress, injury or a breakdown in relationships between cats.
Working with a qualified cat behaviourist can save a great deal of stress, particularly when neighbour relations are involved or when the harmony of a multi-cat household is at risk.
If your cats are fighting, or you are experiencing problems with a neighbouring cat, please get in touch. I would be very happy to help.
ABOUT THE AUTHOR
Anita Kelsey holds a first class honours degree in Feline Behaviour and Psychology (work based BA Hons) and runs a vet referral service dedicated strictly to the diagnosis and treatment of behaviour problems in cats. She is also a qualified cat groomer and specialises in grooming challenging or phobic cats. Anita, a strong advocate of a vegan lifestyle, is based in East Sussex but consults all over the UK as well as international requests. She lives with her husband, a music producer, and 1 Norwegian Forest cat, Kiki.
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Her first book ‘Claws. Confessions Of A Professional Cat Groomer‘ was published by John Blake in 2017 with her second book, Let’s Talk About Cats self published via Amazon worldwide in 2020. The Little Book Of Extraordinary Cats is Anita’s third book out now 2026.
