Prevention. In attempting to prevent territorial aggression, it is always wise to have a separation period when introducing a new cat into the household. The family should confine the cats in separate areas of the home where they cannot see each other. The confinement areas can occasionally be switched (without the cats seeing each other) to allow the new pet the opportunity to explore all areas of the home and to help both pets get used to the other's odor.

Confinement should be followed by a slow, progressive introduction of the cats. To begin, the cats should be allowed to see each other during a low-arousal situation, such as while being fed. To control the speed of the introduction, use crates or harnesses and place the cats far enough apart that they show no aggressive displays. They can then slowly be moved closer together each time they are fed. Another approach is to feed the cats in rooms separated by a screen door or a partially opened door. Start the feedings at the far ends of the rooms, and gradually move the food bowls closer to the doorway.

When the cats show no signs of aggression as they are fed in proximity, the owners can allow them to meet. Owners should assign a person with treats to each cat and station them at opposite ends of a large room. A cat can be kept close to each person by intermittently tossing treats on the floor. Gradually, the treats can be tossed toward the middle of the room, thus controlling the cats' slow approach toward each other. Water guns can be used to interrupt aggressive behavior if necessary. Caution the family against holding either of the cats and approaching the other during the initial meeting.

Intermale aggression

Aggression between male cats is one of the most common forms of feline aggression.¹ As male cats behaviorally and sexually mature, they begin challenging each other. Intermale aggression is particularly common during the breeding season. The aggressive interactions involve posturing, threatening, and fighting. Hissing and growling often occur. Aggressive interactions between male cats may contain elements of intermale and territorial aggression.

Treatment. Intermale aggression is facilitated by postpubertal androgen secretion and is largely prevented or eliminated by castration.¹⁴ Neither the fighting experience nor the cat's age seem to affect the success of castration.¹⁴

Desensitization and counterconditioning may be helpful but are not successful for most cases when used alone. Drug therapy (see "Territorial aggression") may be necessary. When the medication is withdrawn, the cat may become aggressive again. In cases in which aggression persists after castration, separating the aggressive cats may be the only remedy.

Maternal aggression

Intense aggressive displays are common when people or animals approach a queen and her litter. This type of aggression is likely related to the hormonal state of females during lactation as well as to the presence of the young.²

Treatment. Because of the relatively short duration of maternal aggression, simply avoiding the queen may be the most prudent solution. Adequate socialization of female cats when they are young may also help prevent problems. Gently handling and hand-feeding a queen throughout her pregnancy and after parturition may also help.

Pain-induced aggression

Even the most sociable and docile cat may exhibit aggression with handling that elicits pain or discomfort (e.g. when its hair or tail is pulled, when it is stepped on, or when a painful area of the body is touched).¹ Underlying painful conditions such as abscesses, otitis, and arthritis should be ruled out in all cases of aggression.

Although physical punishment can sometimes produce submission and facilitate restraint in social species, it is seldom a satisfactory method for modifying behavior or gaining control, especially in cats.² In most cases, physical punishment either elicits aggression or intensifies the aggression that is already present, and it usually leads to fear and avoidance behaviors.