There are many benefits in adopting a second cat to enrich the life of a single cat who is not too set in his or her ways to accept a newcomer. Two cats living together, as I emphasize in my book Understanding Your Cat (now available as an e-book on my website) are generally healthier and happier than cats who live with no contact ever with their own species.
M.B. from Port St Luice, FL sent me the following useful steps to follow when introducing a new cat which she learned from a friend who helps others with cat problems and has obviously learned from experience how to facilitate the socialization of cats with cats.
I would add that of course you should have a veterinarian thoroughly check any new cat for infectious and contagious diseases, and to treat the cat for internal and external parasites as needed. If there are any doubts about the cat’s health, it should be quarantined for seven to 10 days before bringing it into the home.A blood test for feline infectious diseases would also be advisable, especially for feline immunodeficiency disease. In well-run animal shelters, all of these steps are usually covered, including spay/neuter, so you can take the cat of your choice from the shelter directly home to begin the introduction process with your resident cat(s).
Many cat owners find that using the commercially available feline pheromone Feliway, broadcasting it where the cats are with a plug-in room diffuser, can help them calm down and may facilitate the socialization process.
I find that grooming and massaging each cat in turn, while one is watching the other being handled, and encouaging them to play together using a toy lure on the end of a string tied to a short cane —a cat play-wand can work wonders, along with large boxes or a wide tube made from old carpet for them to play hide-and seek games.Providing a sturdy scratch-post and a climbing cat-gymn or condo ideally located by a look-out window are environmental enrichments which will facilitate their social interactions.
There should be no problems with the cats sharing the same litter box provided that it is cleaned out at least twice daily.