Aggression in Cats


Aggression is the second most common feline behavior problem seen by animal behaviorists. Although cat aggression is sometimes taken less seriously than dog aggression—perhaps because cats are smaller and don’t pursue people to bite them—aggressive cats can be formidable. 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.

What Is Aggression?

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 Cat Body Language

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
  • Head tucked in
  • Tail curved around the body and tucked in
  • Eyes wide open with pupils partially or fully dilated
  • Ears flattened sideways or backward on the head
  • Piloerection (hackles up)
  • In an anxious cat, whiskers might be retracted. In a fearful cat, whiskers might pan out and forward to assess distance between himself and the danger
  • Turning sideways to the opponent, not straight on
  • Open-mouthed hissing or spitting
  • Might deliver quick strikes with front paws, claws out

Overt aggression, whether defensive or offensive, includes:

  • Swatting, striking with paws
  • Biting
  • Fighting
  • Growling, shrieking
  • Scratching
  • Preparing for an all-out attack by rolling onto side or back and exposing all weapons: teeth and claws
  • In this position, your cat might attempt to grab your hand and bring it to his mouth to bite it

Classification of Aggressive Behavior

If your cat has been aggressive in the past or you suspect he could become aggressive, take time to evaluate the situations that got him upset. Who did he aggress toward? When and where did it happen? What was going on during the half-hour or so leading up to the incident? What was about to happen to your cat? Determining the answers to these questions can clarify the circumstances that trigger your cat’s aggressive reaction and provide insight into why he’s behaving this way. You need to understand the cause of your cat’s aggression and his motivation for it before you can help him.

Keep in mind that a number of medical conditions can cause or contribute to your cat’s aggression, including toxoplasmosis, hyperthyroidism, epilepsy, abscesses, arthritis, dental disease, rabies, trauma, and sensory decline or cognitive dysfunction in older cats. The first step in resolving your cat’s aggression problem is to have a complete veterinary exam to assess his physical health.    

Aggressive behavior problems in cats can be classified in different ways. A good way to understand why your cat is aggressive is to think about the function or purpose of the aggression. If you consider all the reasons why cats behave aggressively, you can determine what motivates your cat to do so and identify what he might gain from his behavior.

Between Cats

The most obvious and easily understood type of aggression between cats occurs between unneutered males. As males reach adulthood, they often begin to challenge each other for access to mates and territory. Tom cats who roam will get into threatening stand-offs and actual fights. They sit or stand stiffly, their hackles up, and stare at each other. Their ears are swiveled backward, and they often growl, hiss and howl loudly. One cat might eventually slowly leave, or one or both of them might attack.  

Aggression between household cats is more subtle and complex than the conflicts between two outdoor toms. It can be so subtle, in fact, that cat parents don’t notice it. The aggressor cat postures, and the recipient makes himself look smaller and may break away to avoid the aggressor. The aggression can occur between females or between females and males. It can be related to physical size and activity (large cats often intimidate smaller or less active cats), to a lack of pleasant social experiences with other cats, to an accidentally learned association between the other cat and something unpleasant (like fireworks or thunder), or to a simple personality clash. Please see our article, Aggression Between Cats in Your Household, for more information about this problem.

Fearful or Defensive

Fear aggression can occur when a cat perceives a threat, and it escalates if he can’t escape. The more threatening the person, animal, object or sound seems to the cat, the more heightened his fear reaction will be. Typical body postures associated with fearful or defensive aggression are a combination of defensive signals (such as crouching, flattening the ears, tucking the tail, leaning away or rolling onto the side, and pupil dilation) and aggressive signals (such as hissing and spitting, piloerection, growling, swatting, biting and scratching). Aggressive signals are especially likely to be displayed if a cat can’t escape the thing he fears. Often the best way to deal with a defensively aggressive cat is to simply avoid him until he calms down.   


Animals of many species strive to expel or keep out other individuals from their territory, and cats are no exception. Both male and female cats are territorial, but males may defend larger territories than females. Cats’ territorial aggression is usually directly toward other cats, but it can be directed toward dogs and people, too. A cat can show territorial aggression toward some family members and not others and toward some cats but not others. Cats mark their turf by patrolling, chin rubbing and urine spraying. They may stalk, chase and ambush a targeted intruder while displaying offensive body postures, including hissing, swatting and growling. Some cats take a slow and steady approach in their stalking, while others immediately and aggressively give chase. A cat’s perceived territory could be the entire house or part of it, the yard, the block or the neighborhood.

Some of the most common situations that trigger territoriality are:

  • A kitten in the household reaches sexual maturity
  • A new cat is introduced into the family and household
  • Major changes are made in the cat’s family or environment (for example, moving or someone moving in)
  • Stray or roaming cats in the neighborhood enter a cat’s territory


Rough play is common and natural among kittens and young cats less than two years of age. Despite the playful intentions of a cat, however, when such play is directed toward people or becomes overly rambunctious, it can cause injury to people or damage household items. Play aggression is the most common type of aggressive behavior that cats direct toward their owners. It involves typical predatory and play behaviors, including stalking, chasing, attacking, running, ambushing, pouncing, leaping, batting, swatting, grasping, fighting and biting. It’s believed that through play with each other, young cats learn to inhibit their bites and sheathe their claws when swatting. The degree to which individual cats learn to inhibit their rough play varies, and those who were orphaned or weaned early might never have learned to temper their play behavior. Other factors that can contribute to play aggression are long hours spent alone without opportunities to play, and if pet parents encourage their cats to chase and attack people’s hands and feet in play.


Redirected aggression is probably the most dangerous type of cat aggression because the bites are uninhibited and the attacks can be frightening and damaging. Unfortunately, it’s also a very common type of feline aggression. Redirected aggression occurs when a cat is aggressively aroused and agitated by an animal or person he can’t get at (because there’s a window between them, for example). Unable to get to the trigger of his agitation, he turns and lashes out at someone—person, dog or cat—who is nearby or who approaches him. There can be considerable delay between the initial arousal and the redirected aggression, as long as hours. This is why cat parents sometimes describe this kind of aggression as unprovoked or “out of the blue.” They weren’t even aware of the initial trigger (for example, a cat outside who passed by 30 minutes before the attack). A redirected attack occurs only if an agitated cat is approached or there’s someone close by. The cat won’t go looking for someone to attack! It’s not a malicious or even intentional type of aggression. It’s almost like a reflex, done automatically without thought. This is why it’s never a good idea to break up a cat fight or approach an agitated cat showing defensive or offensive aggression postures.

Some common triggers for redirected aggression are:

  • Watching another cat through a door or window
  • Watching or stalking birds, squirrels or other prey animals
  • Smelling another cat’s odor on a family member, a visitor or clothing
  • Coming indoors after getting outside if the cat usually lives only indoors
  • Hearing high-pitched noises
  • Being frightened or harassed by a dog
  • Having a person intervene in a cat fight
  • Being in an animal shelter, surrounded by the sight, smell and sounds of other cats


Some cats enjoy being petted, held, carried and even hugged. Some merely tolerate these activities with their owners, or they like being petted but not carried. And a few don’t like being petted at all. Petting-induced aggression occurs when a cat suddenly feels irritated by being petted, nips or lightly bites the person petting him, and then jumps up and runs off. This type of aggression isn’t well understood, but behaviorists think that physical contact, like stroking, can quickly become unpleasant if it’s repeated over and over. Repetitive contact can cause arousal, excitement, pain and even static electricity in a cat’s fur. Imagine if someone rubbed your back but, instead of moving his hand all over your back, he rubbed in just one spot, over and over. That could quickly become unpleasant. Your cat might feel the same way: what started out feeling good is now irritating, and he wants you to stop. This type of aggression is more common in males than females. When your cat signals you to stop petting, the best response is simply to stop.

With careful observation of your cat’s communication signals, you’ll usually see warning signs, such as:

  • Quickly turning his head toward a person’s hand
  • Twitching or flipping his tail
  • Flattening his ears or rotating them forward and back
  • Restlessness
  • Dilating pupils

Pain-Induced and Irritable

Pain-induced and irritable aggression are triggered by pain, frustration or deprivation, and they can be directed toward people, animals and objects. Any animal—including humans—can aggress when in pain. So even a well-socialized, normally docile cat can lash out when he’s hurt, when someone tries to touch a painful part of him (for example, to medicate his infected ears), or when he’s in pain and he anticipates being handled because someone is approaching him. Cats with aggression problems should always be examined for underlying medical problems, especially painful diseases such as arthritis, dental pain and abscesses from fighting. Painful punishment is not only ineffective for changing cat behavior, it can also trigger pain-induced aggression and worsen other types of aggression, like fear and territorial aggression. Body postures will usually be defensive.


All mothers have instincts to protect their offspring from potential danger. Maternal aggression can occur when a mother cat (called the queen) with her kittens is approached by people or other animals whom she perceives as a threat. It’s more often directed and other cats, but it can be directed toward people, too. Queens can be quite aggressive when defending their young, especially in the first few days after birth. For this reason, it’s a good idea to avoid handling kittens during the first few days of their lives.


The classification of idiopathic aggression includes any type of aggression whose cause can’t be determined or explained through behavior history or medical exam. Cats with this type of aggression can attack their owners violently. They may bite repeatedly and remain in an aroused state for long periods of time. Redirected aggression must be closely considered and ruled out as a possible cause before a diagnosis of idiopathic aggression is made. These cats are dangerous, and pet parents of such cats should carefully assess their quality of life, as well as the safety of those around them.


Cats are predators, and predatory behaviors are completely natural and highly motivated behaviors for them. Many experts don’t classify predation as aggression because its purpose is to obtain food—unlike other types of aggression, which are responses to conflict. Cats are superb hunters. They use their acute vision and sensitivity to high-pitched sounds to locate their prey. They hunt insects, reptiles, rodents, young rabbits and birds. Most cats specialize in rodents, such as mice and voles, but a few become good at killing birds. When a cat detects potential prey, his predatory sequence of behaviors starts with silent stalking, watching and waiting for the perfect moment to strike (his rear end might wobble from side to side and his tail might twitch). Then he’ll finally sprint toward the prey and strike it with his front paws. If he’s successful, he’ll deliver a killing bite that all cat species use—he’ll bite the prey at the back of the neck to sever the spinal cord. If your cat likes to watch out the windows, you may have seen him become focused, twitch the end of his tail and move his mouth to make a strange chattering sound. When cats do this, it’s because they’ve detected prey that they’d like to hunt.

Always Work with Your Veterinarian

A medical workup is essential for all aggressive cats. Some cats behave aggressively because of a medical condition or complication. In addition to acute painful conditions, cats with orthopedic problems, thyroid abnormality, adrenal dysfunction, cognitive dysfunction, neurological disorders and sensory deficits can show increased irritability and aggression. Geriatric cats can suffer from confusion and insecurity, which could prompt aggressive behavior. Certain medications can alter mood and affect your cat’s susceptibility to aggression. Even diet has been implicated as a potential contributing factor. If a medical problem is detected, it’s crucial to work closely with your veterinarian to give your cat the best chance at improving.

Always Work with a Professional

Aggression can be a dangerous behavior problem. It is complex to diagnose and can be tricky to treat. Many behavior modification techniques have detrimental effects if misapplied. Even highly experienced professionals get bitten from time to time, so living with and treating an aggressive cat is inherently risky. A qualified professional can take a complete behavior history, develop a treatment plan customized for your cat and coach you through its implementation. She can monitor your cat’s progress and make alterations to the plan as required. If appropriate, she can also help you decide when your cat’s quality of life is too poor or when the risks of living with your cat are too high and euthanasia is warranted. Please see our article, Finding Professional Behavior Help, to locate a Certified Applied Animal Behaviorist (CAAB or ACAAB) or board-certified veterinary behaviorist (Dip ACVB) in your area for guidance.

Hetts, Suzanne. (1999). Pet Behavior Protocols. Lakewood, CO: AAHA Press.