Cat: Introducing a New Cat to the Household

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 and appropriate distribution of resources such as litter trays, resting places and water and food bowls. 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 all of its essential resources 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 do 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 essential resources and 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.

This training should occur when the cats can be occupied in a highly "rewarding" activity such as play or eating treats. The cats need to be far enough apart that they are relaxed and will take food while in the presence of the other cat and 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. It is really important that the distance between the cats is noticeable since the idea is not to get the cats to eat together or to move their food bowls nearer to one another. The food is simply used as a focus for the cats to concentrate on, rather than taking notice of each other. If the cats will not eat then they are probably too anxious and too close together so try moving the cats further apart. 

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 (if there is already aggression present then usually the aggressor) to an indoor pen or to restrain it on a body harness (which needs to be introduced appropriately in the absence of the other cat) and lead. In some cases it may be necessary to restrain or confine both cats as this will ensure that neither can escape, and thereby set of a cycle of run and chase, nor injure each other. However, it is best to keep restriction to a minimum. The aim of this introduction is not to bring the cats into close proximity or to persuade them to like each other, instead the aim is for both cats to be able to co-exist under the same roof in an atmosphere of neutral tolerance.

"The aim of this introduction is not to bring the cats into close proximity or to persuade them to like each other, instead the aim is for both cats to be able to co-exist under the same roof in an atmosphere of neutral tolerance."

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. Do not attempt to move the pens progressively closer as this defeats the purpose of the introduction. Instead work to the point where both cats can be loose in the same room, with the pens present at a reasonable distance from one another so that they can act as a retreat location for each cat should that be needed. Do not work toward bringing the cats together to eat next to each other, as you see in this photo, as cats are solitary feeders and being made to eat in close proximity to each other can be stressful. The body language of these three cats shows tension and apprehension and the ears are particularly expressive. Cats should be fed alone and food should only be used as a distractor when the other cat is at some considerable distance from it.

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. Once again the aim is not to bring the cats closer together and get them to play together but to help them to relax in the presence of each other so that they can develop a tolerance that is workable within the same household.

What if aggression develops or persists between the cats?

Despite slow and careful progression, some cats may continue to display aggression, and if this happens it is important to look at the resource distribution within the household and make sure that you are providing separate living quarters, or core territories, 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 and 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 and this option should be discussed with your veterinary surgeon. If longer term treatment is being considered the welfare implications of this approach must be taken into account. If everything has been done to try to establish separate territories for the cats under the same roof but without success then it may be necessary to accept that the cats will never be compatible housemates and that the only way to avoid social competition in these cats is to find a new home for one of them.