Research has shown that kittens are usually more adaptable to being brought into homes with other cats simply because they are young and have not developed their own behavioral habits or personal preferences. Oftentimes older cats enjoy the possibility of helping to ‘raise’ or care for a younger member of their own kind. Also, it has been shown that in general cats may more easily adjust to new members of the opposite sex, but cats of the same sex can get along just as well.
After you have successfully introduced your new cat to their household, adapted them to the scent of your other cat, mixed their pheromones, and engaged them in positive interactions between doorways, the next step is to initiate visualization.
This process should be started only if the cats seem to get along with each up to this point. If there is no hissing or growling at each other under the door and you notice them visibly or visually trying to interact with each other out of curiosity in a positive manner, then you know it is time for the first introduction.
Tips to begin this process include utilizing a screen or baby gate that prevents them from physically interacting at first but still be able to completely see each other. Make sure the barrier you select is secure and high enough that the cats will not be able to climb or jump over it into each other’s spaces. Having another family member or friend assist in this process allows for the restraint of both animals at the same time in the event of a negative interaction.
Once you have established an area where the cats can see each other clearly, begin repeating the same steps you performed when they were in separate locations. Try feeding them near the barrier and evaluating their reactions to each other. It may take some time for them to become comfortable eating together, but begin at a far distance and slowly decrease that distance until they are nearly touching. There is no need to rush any of these processes as it will only result in frustration and two unhappy pets.
Once the cats are okay with being fed together, trying playing with them separately as before, in full view of the other. Make sure your new cat associates interactions between you and your older cat as positive and desirable.
At some point it will be necessary for the cats to be able to co-exist together in the same environment without barriers. As long as there have been no negative reactions from either animal, it is time to remove the barrier and allow them to physically meet one another, although supervision is still recommended. Begin in one room and observe how they act with one another. Purring and playing are positive interactions while hissing, growling, or fighting may indicate the need to go back a step and maintain visual, separated interaction for a longer time period.
Time and patience are your greatest assets in this process and will pay off in the long run by rewarding you with two happy, cohabitant animals who will hopefully become playmates for life.
A few tips for making this process easier includes choosing a seemingly more social, friendly cat from the beginning. Also, going back and having to repeat a step for a longer period of time might be frustrating — but is necessary and will create a happier household in the end, so do not get discouraged. Acclimation takes time and cats adjust to different situations at different rates, the same way humans do.
In some situations, for undetermined reasons, two cats may simply not get along and having a single cat household may be the best idea for your family. As a last resort, seek the advice of a veterinarian or expert animal behaviorist. They should be able to provide some additional solutions to difficult adjustment periods.