Introducing a new cat

How can aggression between cats be prevented?

Problems of aggression between cats in the same household can usually be prevented or minimised with early socialisation, patient and slow introductions of new cats and provision of adequate space, litter trays and food bowls for each of the cats. When a new cat is introduced (or reintroduced) into a household with existing cats, problems can best be prevented by initially keeping the new cat in a separate room with water and litter facilities and supervising all interactions. If both cats have had adequate socialisation with other cats, and are not too timid or fearful in nature, 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 programme of introduction may be required. In order to maximise the success of integrating a new feline resident it can be helpful to install Feliway diffusers in the house prior to the cat’s arrival but in cases where problems arise this product can also be used as part of the treatment approach.

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 programme of controlled and gradual introduction 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 facilities and water. Allow the existing cat to continue to have access to the rest of the home. This arrangement mimics the integration of feral cats into a colony, since it 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 room with a glass door, it may be possible to allow the cats to see each other through a safe partition. When the cats show no fear, anxiety, nor threat towards each other, you can 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 minimise the possibility of aggression, and the reward is sufficiently appealing, the cats will focus on the rewards rather than each other. 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. The cats need to be far enough apart that they are relaxed and will take food while in the presence of the other cat. If the cats will not eat then they are probably too anxious and 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 procedure at same distance at the next feeding. If things go well, next time the dishes can be moved closer together, but only by a small amount.

In addition to ensuring that the cats are at a safe enough distance to minimise fear, you may find it helpful in the early stages to confine one of the cats (usually the aggressor) to an indoor pen or to restrain it on a body harness and lead. In some cases it may be necessary to restrain or confine both cats as this will ensure that they can neither escape, and thereby set of a cycle of run and chase, nor injure each other. If both of the cats have been in indoor pens during the first training session, you can go on to switch them around and place them in each other's pens at the next session (so that they are exposed to each other’s scent). Another technique, which may help, is to rub the cats with towels and switch from one cat to the other to further mix their scents. The pens can be moved progressively closer, provided that the cats show no fear or anxiety and remain interested in the food. Once the cats will eat and accept exposure in either pen when close together, the next stage is to keep one cat in a pen 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 pens. A body harness and lead can be used to ensure additional safety. Over time the cats can be fed closer together until the point where they 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?

Despite slow and careful progression, some cats may continue to display aggression, and it may be necessary to accept that they will never be compatible housemates. The only way to avoid social competition in these cats may be to find a new home for one of them, 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 lead and harness 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 on a short-term basis. If longer term treatment is being considered the welfare implications of this approach must be taken into account. The option of drug therapy should be discussed with your veterinary surgeon.

This client information sheet is based on material written by

Sarah Heath, BVSc, DECVBM-CA, MRCVS & Daniel S. Mills, BVSc, PhD, ILTM, CBiol, MIBiol, MRCVS