Health Topics

Keeping The Peace:

Preventing cat fights in a multi-cat household.

(This article was originally published in the Fall 2008 Issue of Cat Basics and is reproduced here with the permission of the publisher.)

Many cats enjoy the company of other cats, while some cats merely tolerate being together. In some homes, introducing a new cat can be a difficult task. Problems may also arise between cats in homes where there have been no previous problems.

Why so cranky?

Aggression is typically exhibited toward unfamiliar cats that are not part of a colony. Cats can often be integrated into an existing colony or household, but this is usually a very gradual process. In a recent study, about 50 percent of owners reported fighting when a new cat was introduced into a home with existing cats. Fighting was associated with unfriendly behavior at the first meeting (scratching and biting, for example). In most cases it was the new cat that initially displayed fear or aggression, while the resident cat was more likely to try and initiate play. Therefore starting off on the right foot (or paw) is important for achieving long-term success.

Another situation in which aggression might arise is when one cat has been away from home for veterinary care, grooming or perhaps after being lost. When the cat returns there may be a change in odour or appearance of the cat. Problems may also begin if one cat in the home becomes excessively aroused by a cat outdoors and the aggression is then redirected toward another cat in the home. Intact cats may become more aggressive to other cats in the house during breeding times, due to hormonal changes. Since illness, pain and aging can also be factors, a veterinary assessment should be scheduled whenever new behaviour problems arise.


Although cats are born with some feline social skills, experience with other cats is necessary to fine tune these skills. Therefore, adopting multiple cats of different ages and insuring kittens have sufficient social contact with other cats can help prevent poor social relationships with other cats. Some veterinary clinics even offer kitty kindergarten so that cats can play and interact with a variety of cats and people.

Introducing a new cat:

  • When introducing a new cat into a household with existing cats, gradual familiarity should be established using sight, scent or sound, before allowing direct contact. This can be accomplished by housing the new cat in a separate room and making certain that all introductions are gradual and positive.
  • The resident cat should be allowed access to the resources to which he or she is already accustomed and the new cat should be housed in a separate area with new litter, bedding, toys and perches.
  • Before introducing any new cat into a household, a veterinary visit should be the first step to insure the cat has no health problems that might be contagious to your existing cats, to rule out health problems that might interfere with successful introductions, and to get some guidance as to how to proceed.
  • Before introducing cats, consider how they will meet. For example, if cages or body harnesses might be used for exposure, the cats should first be adapted to these restraining devices.
  • It can be useful to train your cat to a few verbal commands such as come, play time or food time or to use clicker training so that the cats can be controlled verbally and reinforced for desirable behaviours.
  • If both cats have had adequate socialization with other cats, and are not too timid or fearful, it may be only a matter of days to weeks before the cats are able to share the territory with little or no fear or aggression.
  • Potential situations for aggression can be reduced by providing sufficient resources to reduce competition such as multiple litter boxes, sleeping areas, feeding stations, and three-dimensional space for perching and climbing. This way, the cats may be able to avoid conflict. It might also be necessary to identify when and where the cats might not get along and to separate the cats into their own areas before problems arise.

Managing aggression

When problems arise between cats, a slow approach with the use of the strongest possible rewards will be required. At first, a lengthy separation into different parts of the home may be needed to ensure that both cats are calm and secure before any reintroduction takes place. In addition, this enforced separation avoids the possibility of further injury and any threats, fearful displays or aggression, which would further aggravate the problem. Ensure that each housing area provides an environment with opportunities for perching, climbing, bedding, scratching, elimination and play. The program for reintroduction is for the cats to be gradually exposed to each other at a level that does not cause any fear or anxiety (desensitization) and to associate favoured rewards with each exposure to the other cat (counter-conditioning). Since each case and household provides its own individual challenges, a behaviour consultation may be necessary to design a reintroduction program. In addition, drugs or pheromones might need to be utilized to help reduce fear, anxiety and aggression.

The reintroduction program

  • Get each cat used to the other's odour by brushing each cat and then using the brush on the other cat while giving favoured food treats.
  • Share play, toys and litter boxes.
  • Allow each cat into the other cat's area for some feeding and play.
  • Begin exposing the cats to the sight of each other while using favored treats, food or toys to ensure a positive outcome. The exposure and counter-conditioning could begin on opposite sides of a glass or screen door, or with one or both cats in crates or harnesses.
  • Bring the cats closer together. As long as the cats eat food or treats, or play with toys without showing any fear or aggression, progress is being made and each future introduction can be slightly closer. However, if at any point either cat will not eat or play, the distance will need to be increased for future exposures.
  • Make sure there are enough climbing, litter, perching, feeding, play and hiding areas that the cats can avoid conflict.
  • It may be most practical to have the cats together only when the owner can supervise to give rewards and ensure safety.

In some homes, establishing any form of satisfactory relationship may not be possible and exposure will need to be limited or entirely prevented. When behavioural techniques, drugs or pheromones are not successful, then permanently separating the cats either in different parts of the home (or possibly in different homes) may be best for the well being of the owners and the cats.