Why are my cats fighting? Part 1: Three reasons your cats might not get along

There are two major reasons people seek help with their cats' behavior. The first is inappropriate elimination. The second is aggression or fighting.

There are several reasons that cats may fight -

1) territoriality

2) play

3) stress or anxiety

1) Territoriality

While cats do not live in packs, they do form social bonds in wild colonies. However, in the wild, cats have much larger territories than they do in our homes. Various studies have been performed in England and the US, tracking feral cats and indoor/outdoor pets. These studies have found that cats have a range of up to 2 square miles in the suburban U.S. and as large as 8.5 square miles in rural farmland in England.

Cats with indoor habitat tend to roam less than feral cats, but still cover a lot of ground.

These studies have shown that cats live more closely together in urban areas where they have more resources available - more sources of food, water, litter areas and "prime" resting spots. We also know that cats establish small territories within a room, and "time share" resources. Cats in a household can be predictably located in certain areas of the home at certain times of day, just like outdoor cats will patrol certain parts of their territory on a predictable schedule. Because of this, cats are very tied to predictability of their environment, and changes to the environment (a.k.a. territory) can cause outbreaks of aggression. Similarly, changes to resource availability - loss of perches, change in feeding location or feeding schedule, changes in the number of people or cats in the home, elimination or relocating of litterboxes - can cause dominance struggles as well, as cats re-negotiate their territories and schedules.

Territorial aggression issues tend to develop when a new cat is introduced into the home without giving the existing cats a chance to acclimate to the idea. It can also be related to the loss of a cat, either because the cat has moved out of the house, has been hospitalized at the veterinary office, or because the cat is no longer living - this can open up a valued resource in the home, causing cats to fight. It may also develop over time as a confident cat starts to guard resources and threaten other cats over these resources, escalating over time (the dominant cat becoming more aggressive and the victimized cat becoming more anxious or fearful). This situation may progress beyond growling and hissing to inappropriate elimination issues (this can be due to due to litterbox guarding by the aggressive cat, territorial marking on the part of either cat, or due to extreme fearfulness on the part of the victim).

2) Play aggression

Cats under two years of age are still honing their hunting skills. It is not unusual for these cats to dash

Play fighting is usually silent, while real fighting is very vocal

madly around the house with the "kitty crazies" as often as several times a day! They pounce and attack anything that moves interestingly - from the dog's tail to your ankle (especially when you're under sleeping under a blanket at 2am!) and this is considered normal and natural behavior at this age. This type of aggression includes all sorts of predatory behaviors that will aid cats in hunting when they are older - pouncing, biting, climbing, stalking, chasing, attacking, running, ambushing, leaping, batting and swatting. This also means that your 14 year old cat may get his fur ruffled when your new kitten wants to pounce his tail 26 times a minute. Most of the time, the wary can avoid attacks from a kitten - watch for a lashing tail, the "butt-wiggle" as they prepare to pounce, a sudden dilation of pupils. Kittens learn "bite inhibition" through play with siblings, and those kittens that were not raised with a litter or who were removed from their mother and siblings at an early age, may be more aggressive than kittens who stayed with other kittens of their age until they were 8 weeks of age. Kittens that spend long hours in a house by themselves, or kittens that are encouraged to view human body parts (hands, arms and legs) as acceptable toys may display more intensely aggressive play behaviors than cats in a multi-cat household.

3)  Stress or anxiety

Many times, cats will become aggressive when they are uncomfortable with a situation. Perhaps your

cat is frustrated that he can't hunt the chipmunk that teases him through the window, or go out and

Stress and frustration can cause cats to act aggressively

explain to the neighbor's cat that the back yard is HIS territory, not hers. Perhaps you have a pregnant female who becomes anxious when you handle her kittens. Perhaps your elderly cat becomes stressed when you pet him over his arthritic hips. All of these scenarios are potential causes of stress or anxiety in a cat - in addition to the stress of living in a multi-cat household, establishing time shares and territory in an indoor range, sharing litterboxes and feeding stations.

Now that you know some of the reasons that cats may fight, stay tuned to discover what you can do about it!


The paper, “Home Range, Habitat Use, and Activity Patterns of Free-Roaming Domestic Cats,” is available online or from the U. of I. News Bureau. 

Why are my cats fighting? Part 2: Fighting Styles
Why are my cats fighting? Part 3: Finding solutions - the 5 "R"s