Diagnosing and treating inter-cat aggression (Proceedings)


What produces stable social groups with little to no overt aggression and high levels of affiliative behavior?

What produces stable social groups with little to no overt aggression and high levels of affiliative behavior?

  • Group size (regardless of space)?

  • Related? Specific relationship?

  • Familiarity with each other?

  • Space per cat?

  • Management issues?

Access to toys, dispersion of food, type of food, trees to climb on, access to natural prey, etc.

  • Breed?

  • Individual differences?-genetic, specific learned experiences

Time together

For pairs of cats, the longer they have been together, the less overt aggression occurs. This is consistent with the formation of stable dominance relationships which rely on dominance signaling, rather than overt aggression.


Relatives and cats that a given cat is more familiar with are more likely to be nearest neighbors than non-relatives and cats a given cat is not familiar with. Being related is more important than familiarity.

Socialization of kittens and juveniles

Socially competent adult cats play an important role in the socialization of kittens and juveniles

Raising kittens?

Extensive social learning occurs from 2-16 weeks and beyond.

Raising cats from 5-6 weeks onward with no contact with their own species can result in serious incompetence in social skills.

Intraspecies Aggression: a selected list

  • Introduction of a new cat

  • Dominance-related Aggression

  • Fear Aggression

  • Play Aggression

  • Arousal-related Aggression

Introduction of a new cat

  • Cat societies are insular.

  • Strangers are not readily accepted.

  • When a new cat is brought into the house, do not simply put it in the same room with the other cats and hope things will work out.

  • Kittens and juveniles are generally easier to introduce than are adults.

  • Gradual exposure with rewards for appropriate behavior.

  • Keep the new cat in a separate room from cats established in the household.

  • Rotate the cats location in the house so that they can be exposed to each others scent.

  • If possible, separate by glass (allows sight and sound) or screen (allows sight, sound and scent) door.

  • Do not force interactions. Allow the cats to approach or leave the door freely.


  • Door tied and blocked so opens about 1 inch

  • Stacked baby gates

  • Get several small cloths, such as washcloths.

  • Rub the perioral area of a cat

Make it a pleasant experience

  • Rotate the cloths

  • Exchange bedding

If significant aggression occurs, use systematic desensitization and counter-conditioning

DS & CC: cat to cat


  • This method will only work if the cats are comfortable being shut in a cage.

  • Put treat (food and/or toy) in cage.

  • If both cats aggressive, put both cats in cages

Gradually move the cages closer over many days

  • If only one cat is aggressive, put the aggressor in the cage.

Allow the other cat to move around freely and choose when to approach.

Approach can be encouraged but not forced with play and treats, e.g. move food bowl a little closer to the cage each day.

Human handlers

  • One person responsible for each cat

  • Ideally, have the cats in harnesses

  • Take cats to distance necessary for relaxation and focus on treats and play

  • Over several to many days, gradually move the cats closer to each other

Dominance-related Aggression

Cats have previously established a relationship, i.e. not a "new cat" issue.

Aggressor chases, growls, and attacks other cat or cats. Shows dominance postures, e.g. ears up and rotated to the side, but does not stop at simple posturing and control of space. May totally control resources.

Attacked cats may respond with

  • similar behavior, resulting in significant fights

  • fear aggression, usually resulting in chasing and control of resources by the dominant cat, but there may be fighting

  • or fear and hiding, resulting in the subordinate cat not having access to essential resource

Problems of dominance aggression may present as an elimination behavior problem

A subordinate cat may be blocked from access to resources, including

  • Litterbox

  • Food

  • Preferred sleeping area

May be but is not always initiated by an identifiable disruptive event, e.g.

  • Illness of one cat

  • Fight that occurs as a consequence of displaced aggression when strange cat approaches home

  • New cat added to household disrupts existing relationships

May present as different problem, e.g. elimination behavior problem

  • High ranking cat or cats control resources (e.g. litterbox)

  • Low ranking cat or cats will be attacked if they approach the resource, as well as in other contexts.

  • Therefore, they avoid the litterbox and eliminate elsewhere.

Dominance Aggression-Treatment

  • In multi-cat households, identify which cats still get along and keep them together as much as possible

  • Keep cats that are in conflict separate when not being supervised

Punish the aggressor

Select cases—make sure requirements for successful use of punishment can be met. Every time

  • Watch cats when they have access to each other

  • Immediately

  • Punish during initial threats that reliably are followed by an attack

  • Do not wait for actual attack

  • Appropriate punisher E.g. Water sprayer

Desensitize and Counter-condition as described in Introduction of a New Cat.

  • If individual cats have a preferred core area, conduct desensitization in a neutral area

  • Rub towels on all cats in the house daily (scent exchange)

Aggressive/Dominant cats-

Serotonin Reuptake Inhibitors

  • Fluoxetine (Prozac®)

  • Paroxetine (Paxil®)

  • Sertraline (Zoloft®)

  • Clomipramine (Clomicalm™, Anafranil®)

Avoid medications with some, but little SRI effect, e.g. Amitriptyline


Cats that have previously been timid in the face of repeated attacks may turn on their attacker. This can be beneficial or harmful, depending on the situation.


Many owners report that their cat becomes more "affectionate", rubbing them, sitting in their lap and otherwise seeking contact with them for greater frequencies and durations

Fear Aggression

  • Cat hisses and growls at other cats when they come near or are seen.

  • Shows signs of fear, e.g. ears back, crouching, urinating.

  • Usually hides rather than chasing and attacking, but may chase.

  • When occurs between cats that have historically gotten along well, usually initiated by classical conditioning.

Classical Conditioning

  • US (Something SCARY) ->UR (Fear with aggression)

  • US + NS (Buddy)->UR (Fear with aggression)

  • NS (Buddy) becomes CS ->CR (Fear with aggression)

  • Fear Aggression-Treatment

  • "Safe place"

Keep cats separate when not being supervised.

  • Antianxiety medication



  • Desensitization

  • Counter-conditioning

Fear Aggression-Treatment

  • Supervise carefully when cats have access to each other

  • Make sure any subordinate cat has regular access to critical resources, e.g. food, litter.

Intraspecies Play Aggression

  • Bouts of wrestling play escalate

  • Wrestling Play is Normal

Normal behavior?

  • Is either cat being injured?

  • Does one cat end or attempt to end the play bout when the intensity of play escalates?

  • Does the other cat allow termination of play that is escalating in intensity, or does it continue the escalation from play to fighting?

  • If the answers are No-Yes-Yes, this is normal

Intraspecies Play Aggression-Treatment

What if play does escalate into fighting?

  • Keep separate when not being supervised

  • Allow play when supervised, but disrupt play when escalation begins

  • Do not wait for escalation to reach the point of actual fighting

  • May be more of a problem with cats that were raised in social isolation from their own species and have not learned appropriate social behavior

Arousal related aggression

  • Identify the cause of arousal and treat that

  • May need to separate cats at certain times of the day

  • Medication



"When winning or losing is determined by the location of the contest arena, and when that produces learning specific to location, then we may invoke the concept of "territoritality". In such cases we acknowledge that the directionality of the agonistic relationship is predictable based on geography."

Bernstein, 1981. Dominance: The baby and the bathwater

Territorial Aggression

  • Defense of a specific area by one or more cats against others?

  • True territorial defense in this species has not been verified by empirical scientific studies.

  • There is no such thing as a "floating territory". Cats that aggress and win against other cats that enter their personal space are higher ranking in the dominance hierarchy.

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