Non – Recognition Aggression in Cats

One of the most bizarre types of feline aggression occurs between cats when one cat is brought back from the veterinarian's office following some medical or surgical procedure. For some reason, the cat that remained at home may not to recognize his former buddy and may attack savagely. It can only be assumed that this is a case of mistaken identity and that the signals the returning cat put forth are somehow perceived as hostile or threatening.

Who's Doing What to Whom?

The characters of the two cats are normally:

The Cause of Sudden Change of Attitudes

The Clinical Picture

The mode that the attacker cat adopts is sometimes that of feline affective defense behavior.
Features are:

The attacked cat may flee if he can, or may hunker down and try to make himself invisible.

Attacks may be savage and fur will often fly. Persons attempting to intervene may find themselves the subjects of the incumbent's aggression. Cats that are this wild will often redirect their aggression onto the nearest person or object.

What to Do

The first thing to do is to separate the two cats while simultaneously making sure that you do not become the target of the cat's aggression. Ideally the aggressor should be encouraged or herded into a separate room – such as a bathroom – giving him time, plenty of time, to settle down. Typically, a cat so enraged will take several hours to settle down. Even leaving the cat incarcerated overnight, with sufficient provisions and a litter tray, may not be overkill. The reintroduction of the two should only be attempted when the aggressor has completely settled down and is back to his old self. Even so, it should be accomplished tentatively and with escape routes planned. Reintroducing the two cats across a screen or via an inch crack in a door is a good plan so that the cats' attitude toward each other can be assessed before a full frontal introduction.

The Outlook

The chances that the cats' relationship or at least tolerance of each other can be reinstated are good, but future meltdowns are likely once this sensitivity has been recognized. In other words, history is likely to repeat itself if steps are not taken to prevent recurrence. Useful measures to take are as follows:


It is almost impossible to prevent non-recognition aggression entirely. Whatever steps and measures you take there is always a chance that the behavior will be repeated. This is not to say that the measures to reduce the incidence are not worthwhile, just that there are no guarantees. The fundamental problem seems to involve the nature of the aggressor.

Content Provided By

This article was excerpted from the CD entitled "Behavior Problems in Cats – Etiology, Diagnostics and Treatments" by Dr. Nicholas Dodman, Professor of Clinical Sciences at Tufts University, School of Veterinary Medicine, © 1998, Trustees of Tufts College. To buy a full copy of the CD, contact .