Causes of Sudden Aggression in Cats

Jessica Vogelsang, DVM
By Jessica Vogelsang, DVM on Mar. 6, 2017

You’re on the couch, petting your purring cat just like you have on many previous quiet evenings. She turns on her side as you rub her belly, and she kneads her paws in contentment. Then, before you know what happened, she hisses and bites your hand. What gives? What happened to turn your mild-mannered cat into Cujo?

Unfortunately, aggression is not uncommon in felines; in fact, it’s the second most common reason for a visit to a behaviorist. Sudden aggression in cats is a scary and frustrating problem for many owners, who fear the unpredictable nature of the kitty fury as well as the physical damage he or she can cause in the throes of an attack. In addition to the painful nature of cat bites and scratches, they can also transmit diseases such as cat scratch fever or serious bacterial infection. Cat aggression is truly no laughing matter.

What Does Aggression in Cats Look Like?

Although owners often report a cat attacking out of nowhere, cats often exhibit subtle changes in body positioning before launching into an actual act of aggression. These postures may be a clue in pinpointing the trigger for the aggressive behavior, as well as a much-needed warning before future attacks.

Defensive postures are intended to make a cat look smaller and position herself in a protective manner. These postures may include: crouching, flattened ears, turning away from the person, hissing, swatting at you, raised hackles, or a tucked head. A defensive cat is often experiencing fear or anxiety about a situation that may or may not be apparent to you. You can be the recipient of fear-based aggression even if you’re not the one causing the anxiety.

Offensive postures make a cat look big and intimidating. These postures include: stiffened legs

  • Hackles raised

  • Moving toward you

  • Staring at you

  • Upright ears

  • Growling

  • Stiff tail

In either case, you want to avoid interacting with a cat exhibiting these postures as they are on the brink of moving on to the real damaging moves. A cat in attack mode can move with startling speed and aggression, and inflict extensive damage in a very swift period when the mouth and all four paws are engaged.

What Causes Sudden Aggression in Felines?

Cat aggression falls into a number of categories. Taking a full and complete history about where the cat was located and what was happening right before the aggressive behavior began is a key component in determining the cause.

Fear Aggression

Fear aggression is triggered by a cat who perceives a threat that he or she cannot escape. This can be a learned behavior based on past experience, and you may not be entirely sure exactly what the cat is fearful of.

Aggression Due to Medical Issue

Aggression with a medical origin is also common.

Pain is the most sudden medical cause for sudden aggression, particularly in older cats or those who have always had a calm temperament. Arthritis, dental disease, trauma, and infections are just some of the conditions that can cause pain and subsequent aggression when a cat is touched or thinks he or she might be touched, in a painful area. In addition to pain, cognitive decline, a loss of normal sensory input, or neurological problems can all lead to aggression.

Territorial Aggression

Territorial aggression happens when a cat feels an intruder is infringing on his or her territory. While often directed at other cats, people and other animals may be the subject of the aggression as well. Triggers may include introducing a new pet or even a new person into the house, a recent move, or new cats in the neighborhood.

Status Aggression

Status aggression occurs when a cat attempts to run the house. Cats who growl when you try to move them, block doors, or bite you when you pay attention to another pet may be asserting themselves in this manner.

Petting-Induced Aggression

Petting-induced aggression, the type described in the opening paragraph, occurs when a cat who enjoys being pet suddenly changes his or her mind. It’s thought that the repetitive motion over time turns from pleasant to irritating.

Redirected Aggression

Redirected aggression is one of the most unpredictable and dangerous types of feline aggression. In these cases, a cat is in a hyper-aroused state by some sort of external stimulus—an animal outside, squirrels running by that he can’t chase, a frightening noise or smell. In your blameless state, you walk by and wind up on the receiving end of this pent-up outburst, seemingly out of nowhere.

What Should I Do If My Cat Experiences Sudden Aggression?

The first stop any time a cat shows these aggressive signs without obvious provocation is your veterinarian. She can examine your cat and make sure he does not have a medical condition causing the unwanted behavior. If your cat has a clean bill of health, your veterinarian can refer you to a behaviorist who can help determine the triggers of aggression and the steps you can take at home to resolve the problem.

In many cases, simply being aware of the early signals of a cat about to freak out gives you the chance to remove yourself from the situation before it escalates to violence. While you can’t always control the causes of the anxiety, owners can often give the cat the space he or she needs to wind down without injuring anyone. With patience and some good detective work, many cats are quickly back in everyone’s good graces.

Want to learn more about the diagnosis and treatment of aggression in cats? Read an overview of the condition.

Jessica Vogelsang, DVM


Jessica Vogelsang, DVM


Jessica Vogelsang, DVM, is a person who loves too many topics to be able to stick to one descriptor: writing, dogs, communication, cats,...

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