Why Cats Fight: The Main Causes and Solutions

Cats are adorable, but they can also be aggressive. They have five potential weapons (their teeth and all four clawed paws) compared to a dogs’ sole weapon of his or her mouth. Cats can bite and inflict severe lacerations, which are painful and can easily become infected. They can also cause cat scratch fever, a usually benign but potentially serious infectious disease that causes flu-like symptoms. Fights between cats rarely result in fatalities, but they can lead to infections and result in considerable veterinary expenses for cat parents. Aggressive cats can be risky to have at home and can pose a real danger to family and visitors.

Aggression is the second most common feline behavior problem seen by animal behaviorists ¹. Aggression is threatening or harmful behavior directed toward a person, another cat or other animals. Virtually all wild animals display aggression to guard their territories, defend their offspring and protect themselves if attacked. Aggression refers to a wide variety of complex behaviors that occur for different reasons under various circumstances. In pet cats, aggressive behavior can range from cats who hiss and avoid the target of their aggression to cats who attack.

Understanding what cats are communicating through their body language is essential for cat parents. It enables them to more accurately “read” their cats and understand their feelings and motivations for doing what they do. It also helps them respond more effectively to behavior issues like aggression. Body language is made up of cats’ body postures, facial expressions, and the position and carriage of certain body parts, like ears, tail and even whiskers. Cat body language is more subtle than dog body language and can be harder for people to interpret. Knowing the basic postures and what they mean can help cat parents deal with problems more effectively and enjoy their cat’s company more fully because they can understand a common language.

Threats and aggression can be either offensive or defensive. An offensively aggressive cat tries to make himself look bigger and more intimidating, whereas a defensively aggressive cat adopts a self-protective posture and tries to make himself look smaller. The following are typical postures seen in feline aggression. A rule of thumb is to not touch, attempt to reassure, or punish cats showing these postures!

Offensive postures include:

A stiff, straight-legged upright stance
Stiffened rear legs, with the rear end raised and the back sloped downward toward the head
Tail is stiff and lowered or held straight down to the ground
Direct stare
Upright ears, with the backs rotated slightly forward
Piloerection (hackles up), including fur on the tail
Constricted pupils
Directly facing opponent, possibly moving toward him
Might be growling, howling or yowling

Defensive postures include:

Crouching with the legs and tail pulled in under the body
Flattening the ears against the head
Turning the head to the side so the whiskers don’t get damaged in a fight
Rolling slightly to the side
Dilated pupils
Open mouth, hissing or spitting
Might deliver quick strikes with front paws, claws out

There are a number of different types of aggression that cats can display, and in some cases, a cat may display more than one type at a time. Here are some general principles for managing all types of feline aggression:

Early intervention is best.
Any type of physical punishment can increase a cat’s fear or anxiety and worsen aggression.
Medications may help, but only in combination with behavioral and/or environmental modification.
Recognizing aggression and startling an aggressive cat without physical contact is usually effective.
Avoid situations that you know make a cat aggressive.
Separate cats that act aggressively toward each other and reintroduce slowly with positive reinforcement, as described in the Territorial Aggression section.
Food treats are excellent positive enforcers of non-aggressive behavior.
Aggression that cannot be managed using the techniques outlined in this article may require consultation with a veterinary behaviorist. It is important to use the information presented here in close collaboration with your veterinarian.

The first step in managing an aggressive cat is to ensure that there is no medical reason for aggressive behavior. Some medical conditions, such as hyperthyroidism, arthritis, dental disease, or infections can cause pain or irritability that can trigger aggression. Some medications, such as steroids, can also increase aggression. A thorough physical examination and blood tests may be necessary to rule out any underlying health problems. If your cat is healthy, the next step is to identify the type and cause of aggression. Here are some of the most common types of aggression in cats and how to deal with them.

Territorial Aggression

Cats are very territorial animals, and they may defend their territory from an intruder, whether it is another cat, a dog, or a human. Territorial aggression can occur between cats that live together or between cats that are strangers to each other. It can also occur when a new cat is introduced to a household, or when a resident cat is reintroduced after a period of absence, such as a veterinary visit or a stay at a boarding facility.

Territorial aggression can manifest as chasing, swatting, biting, hissing, growling, or blocking access to resources, such as food, water, litter boxes, or sleeping areas. Territorial aggression can be reduced by:

Spaying or neutering your cats, which will decrease their hormonal drive and territorial behavior.
Providing enough resources for each cat, such as food bowls, water bowls, litter boxes, scratching posts, toys, and hiding places. The rule of thumb is one per cat, plus one extra. These resources should be distributed throughout the house, not clustered in one area, to avoid competition and guarding.
Creating separate areas for each cat, where they can have their own space and feel secure. This can be done by using baby gates, cat doors, crates, or carriers. You can also use vertical space, such as shelves, cat trees, or window perches, to create more territory and allow cats to escape from each other.
Introducing new cats gradually, following a careful protocol that involves keeping the cats separated at first and then allowing them to see and smell each other through a barrier, such as a screen door or a baby gate. Then, you can progress to supervised interactions, using food treats, toys, or play to create positive associations. This process can take days, weeks, or even months, depending on the cats’ personalities and reactions. You should never force the cats to interact or punish them for showing aggression. If the cats show signs of stress or aggression, you should go back to the previous step and proceed more slowly. For more details on how to introduce cats, you can read this article ².
Using synthetic pheromones, such as Feliway, which can help reduce stress and anxiety in cats and promote a sense of calm and harmony. Pheromones are natural chemicals that cats produce and use to communicate with each other. Feliway mimics the facial pheromone that cats use to mark their territory as safe and familiar. You can use Feliway diffusers, sprays, or wipes in your home to create a more peaceful environment for your cats.

Inter-male Aggression

This type of aggression occurs when two male cats fight over a female cat, especially during mating season. It can also occur between male cats that are not neutered, as they tend to be more dominant and territorial. Inter-male aggression can result in serious injuries, as well as unwanted pregnancies and the spread of diseases, such as feline immunodeficiency virus (FIV) or feline leukemia virus (FeLV).

Inter-male aggression can be prevented by:

Neutering your male cats, which will reduce their hormonal drive and territorial behavior. Neutering can also lower the risk of developing certain health problems, such as prostate disease or testicular cancer. Neutering can be done as early as eight weeks of age, but it is never too late to neuter an adult cat.
Keeping your cats indoors, which will prevent them from encountering other male cats that may trigger a fight. Indoor cats are also safer from other hazards, such as cars, predators, or poisons. You can enrich your indoor cat’s life by providing him with toys, scratching posts, window perches, and interactive play sessions.
Separating your cats if they show signs of aggression, and reintroducing them slowly with positive reinforcement, as described in the Territorial Aggression section.

Defensive Aggression

This type of aggression occurs when a cat feels threatened or scared by another cat, and tries to protect himself by attacking or fleeing. This can be caused by a lack of socialization, a traumatic experience, or a sudden change in the environment. Defensive aggression can also occur when a cat is in pain or discomfort, and wants to avoid being touched or handled.

Defensive aggression can be reduced by:

Providing your cat with hiding places, toys, and positive reinforcement, which can help him feel more secure and confident. You can use cardboard boxes, paper bags, tunnels, or cat beds to create safe havens for your cat. You can also use toys, treats, or praise to reward your cat for being calm and relaxed.
Avoiding situations that trigger your cat’s fear or anxiety, such as loud noises, unfamiliar people, or other cats. You can also use environmental modifications, such as curtains, blinds, or window film, to block your cat’s view of potential threats outside. You can also use synthetic pheromones, such as Feliway, to create a more calming atmosphere for your cat.