Your older cat is easy going and slow. She still has a lot of life in her but you'd like to get another cat as well. You know your existing cat is tolerant of children and other pets, but what will happen when you bring the new cat home?
It may surprise you, but even cats who have been housemates for many years - even siblings - can become aggressive and territorial if one of them is gone for even a few days. So if you have two cats and take one to the vet overnight you may be starting at square one when bringing the cat home. It is important to have some techniques in your 'bag of tricks' to deal with this situation should it occur.
Cats are VERY territorial. They will easily adopt an entire house whether it's 700 square feet or 3000.
The first and most basic step to take is to give the new, or returning cat, a secluded area within the home along with it's own litter box and feeding dishes. This allows the original cat to have 'ownership' of most of the home while allowing both cats to become familiar with each other's scent.
If the secluded area can be viewed through a glass door (such as a sunroom) the cats will also have opportunity to view each other without physical contact.
It is important to avoid ANY aggressive acts on the part of either cat.
Start introducing them into the same physical space by using feeding or playing times together. This will keep their attention on the task and not each other. It will also cause them to associate good things with the other cat's presence. This is the ONLY time the cats should be in the same area.
At first you may wish to have them feed at a good distance from each other with some barrier such as cages or harnesses. This will prevent any attacks or retreating.
The activity MUST engage them. If they are not eating then they are still having too much anxiety. Try more distance or possibly use a spray like Feliway which is a synthetic pheromone spray. Although not proven, it replicates the natural cat pheromone that is friendly and may calm anxiety when sprayed around the home.
Once the cats are willing to eat or play separately and at a protected distance, than you might try rubbing the cats with the same towel and mixing their scents - or alternating the cages so they become accustomed to each others smell during feeding.
It requires a lot of patience to introduce cats. Very slowly decrease the distance from each other. When they are able to eat fairly close and confined then increase the distance again and allow them to eat with no confinement. Slowly decrease the distance and never allow unsupervised contact until you are confident in their behavior.
If serious problems still persist you may wish to contact your vet or may have to consider one cat being removed from the home or keeping them in separate areas indefinitely.
