What is territorial aggression?

Territorial aggression may be exhibited toward people or other animals (usually cats) that approach or reside on the pet's property. Aggression can occur towards outside cats and also to cats that live in the household, especially new cats coming into the territory. This can occur with the addition of another cat, or when resident cats reach social maturity at 1-2 years of age. Another situation is when one cat is removed from the household (perhaps for routine surgery or boarding), and aggression is exhibited when the cat is brought back into the home. This may be either one or both of territorial and fear aggression (perhaps the returning cat smells, looks or acts unfamiliar in some way).

Territorial aggression can manifest as stalking, chasing and aggressive encounters, which may lead to injury. At times the aggressor will prevent the victim from having access to certain areas of the home resulting in a cat that lives on top of furniture or bookshelves or under beds. This may in part be related to the social relationship (status) of each cat (see our handout on ‘Aggression – introduction to aggressive behavior').

How can territorial aggression be prevented?

Territorial aggression can be prevented or minimized with early socialization, patient and slow introductions of new cats and adequate space, litter boxes and food bowls for cats. However, when a new cat is introduced (or reintroduced) into a household with existing cats, problems can best be prevented by slowly introducing the new cat to the environment, by keeping the new cat in a separate room with water and kitty litter, and supervising all interactions. If both cats have had adequate socialization with other cats, and are not too timid or fearful, it is usually only a matter of time before the cats work things out on their own, and are able to share the territory with little or no aggressive displays. However, in some homes, the aggression between cats persists and a more formal desensitization and counter-conditioning program may be required.

What is the best way to safely introduce (or reintroduce) a cat into the household?

In order to ensure that there are no injuries and that all introductions are positive a desensitization and counter-conditioning program is the best way to ease a new cat into a household. Begin by confining the new cat to a room or portion of the home with its own litter box, food and water. Allow the existing cat to continue to have access to the rest of the home. This arrangement provides a separate territory within the home for each cat, and allows both cats an opportunity to adapt to the smell and sounds of each other, without the possibility of direct contact or physical confrontation. If the new cat is housed in a screened-in porch or a room with a glass door, it may also be possible to allow the cats to see each other through a safe partition. When the cats show no fear, anxiety, or threat toward each other, then progress to controlled exposure exercises. Training should occur when the cats can be occupied in a highly "rewarding" activity such as feeding, play, or treats. Provided both cats are far enough apart to minimize the possibility of aggression, and the reward is sufficiently appealing, the cats will focus on the rewards rather than each other. In addition, if the rewards are saved exclusively for these introduction times, the cats will quickly learn to expect "good things to happen" in the presence of each other. In addition to ensuring that the cats are at a safe enough distance to minimize fear, both cats (or at least the one that is likely to be the aggressor) can be confined to an open wire mesh cage or a body harness and leash. This will ensure that the cats can neither escape nor injure each other. It is safest to begin the first few introductions, not only at sufficient distance to reduce fear, but also with one or both cats in cages or on body harness and leash, so that they can neither retreat, or injure the other cat. (See also our handout on ‘Behavior modification – reducing fear and anxiety – desensitization, counter-conditioning and flooding'). If the cats have been in cages during the first training session, they can be placed in each other's cages at the next session (so that the cats are exposed to the other cat's odor). The cages can be moved progressively closer, provided the cats show no fear or anxiety and remain interested in the food. Once the cats will eat and accept exposure in either cage when close together, keep one cat in the cage and the other out during feeding. The situation is then reversed at the next session. As a final step the distance between cats can be increased again, with both cats out of their cages. A body harness and leash can be used to ensure additional safety. Over time the cats are fed closer together until a point where the cats can eat, or take treats, in each other's presence.

Another way to integrate cats is with play therapy. Some cats are more interested in play, toys or catnip than they are in food. One of the best toys is a wand type or fishing rod type handle with a stimulating play toy such as a catnip mouse or feathers on the end for chasing and pouncing. Begin by having both cats play at a distance from each other. Over time, introduce the toys between the cats and let them play with the toys together.

What if the aggression between the cats persists?

Introductions must be done slowly. The cats need to be far enough apart that they are relaxed and will take food or a treat while in the presence of the other cat. If the cats will not eat then they are too anxious and probably too close together. Try moving the dishes further apart. If the cats still will not eat, be certain that they remain apart and do not give any food until the next feeding session. If the cats eat at that time repeat the same distance at the next feeding. If things go well, the next time the dishes can be moved closer together, but only by a small amount.

This is a slow process; you cannot rush things. Allowing either cat to interact in an aggressive manner sets the program back. The cats must remain separated except for times such as feeding when the cats are distracted, occupied, and engaged in an enjoyable act. In other words, good things are associated with the presence of the other cat. Another technique, which may help, is to rub the cats with towels and switch from one cat to the other to mix their scents.

Despite slow and careful progression, some cats may continue to display aggression, and it may be necessary to accept that they may never be compatible housemates. The only way to avoid territorial competition in these cats may be to find a new home for one of the cats, or to provide separate living quarters for each cat within the home. If the cats get along at certain times of the day, they can then be allowed limited exposure and interaction at these times. A leash and harness, or perhaps an air horn or water rifle, could be used to safely separate the cats should any aggressive displays emerge. If the problem is too severe, it may be helpful to medicate one or both cats. The option of drug therapy should be discussed with your veterinarian.

This client information sheet is based on material written by Debra Horwitz, DVM, DACVB and
Gary Landsberg, DVM, DACVB. © Copyright 2002 Lifelearn Inc. Used with permission under license. March 11, 2004.