When a cat is frightened or startled, its reaction may be redirected to the nearest available individual or object. In a multi-cat household, this target may be another cat.

Redirected aggression is swift and intense, and may begin a cycle of persistent aggressive interaction. The spontaneous eruption can occur between housemates that previously coexisted peacefully. It may subside within moments but, more commonly, several days or even weeks may pass before the housemates resume normal relations. Sometimes the relationship between cats is permanently changed.

In a multi-cat household, the target cat is not necessarily the first victim of the aggressive outburst, though usually it is. Occasionally, the roles may be reversed and the aggressor becomes the target cat.

After the initial conflict, a vicious cycle may form between the target cat and its aggressor. In anticipation of an attack, the target cat typically assumes a defensive, fearful and cautious attitude, which triggers the attacker’s pursuit. Long after the original episode has passed, the aggressive cat may be aroused simply by the target cat’s hesitation. The dominant cat may appear to chase the other as a kind of game.

To avoid further problems, separate the cats as quickly as possible after the first episode. Avoid injury to yourself by trying to separate one from the other. It is safer to let the tension subside and then deal with any injury inflicted on the target cat.

Neither cat should be permitted the run of the house. Confine each cat separately, each with its own litter, food and water for at least 7 days. Wait an extra 24 hours after the time when they both appear calm and content. Then release one cat at a time to readjust.

Extend the period of confinement by another day if there is any sign of aggression. Alternate with each cat so that periods of confinement are gradually briefer and periods of freedom are longer. Eventually, both cats can be briefly allowed out at the same time, perhaps at mealtime. If there is any aggression, remove the food and confine the aggressive cat, or both if necessary. Try again later.

It can be very helpful to place the dominant cat on Prozac for 2 months or tranquilize using a medication called amitriptyline during this recuperative period. Both cats are anxious, agitated and aroused, and these anti-anxiety medications, prescribed by your veterinarian, can help prevent permanent problems. Continue medicating both cats until neither is disturbed by the other’s presence.

I would like to acknowledge the work this article is taken from : Instructions for Veterinary Clients: Canine and Feline Behavior Problems, Second edition, Mosby, 1997, pp37-40 by:

Dr. Stefanie Schwartz, DVM,MSc,DACVB
Diplomate, American College of Veterinary Behaviorists
Director of Behavior Services, VCA South Shore Animal Hospital
Clin.Asst.Prof., Tufts University School of Veterinary Medicine
National Consultant, Antech Laboratories