Settling a new cat in your household takes time and patience. Remember, the cat is being introduced to territory already “claimed” by your resident pet, so you need to take both cats' feelings into account.
In addition, it is your responsibility to protect the health of your resident pets and the newcomer. For instance, many cats that are adopted from shelters have upper respiratory infections (URI's) either brewing or obvious. It is important for a cat with such an infection to be treated as soon as possible. Make sure to keep your new cat completely isolated from your other cats for at least a week, or until the infection has completely cleared up before attempting introductions.
Tests for Feline Leukemia Virus (FeLV), Feline Immunodeficiency Virus (FIV) and Feline Infectious Peritonitis (FIP) should be performed on your new cat. These diseases can be lethal to cats so it is important to make sure that your new cat is not a carrier. A fecal test should be performed before the cats begin sharing litter boxes - to check for internal parasites.
Check your resident cat's vaccination status to make sure he is sufficiently well protected against diseases the newcomer may be harboring.
Upon bringing your new cat home, put him into a private room for his first week. This is where your new cat will begin to settle into his new home. Your resident cat should not be allowed to enter this room or to stay at the door growling and hissing.
You will need additional “infrastructure” to support your cats. Obtain new food and water bowls, an extra litter box (or two), scratching posts/pads, various toys, and bedding for the new cat. Obtain the same type of food that the “new” cat was eating in the previous home. If you choose to switch the cat's ration, do so gradually over a two-week period to decrease the chances of causing diarrhea.
Cat to Dog Introductions
Follow the above guidelines when introducing a cat to a resident dog. At the time of the first introduction, apply a leash to the dog and occupy it with some obedience exercises (sit-stay) with food treats as a reward for calm responding.
Cat to Bird or Small Mammal Introductions
Cats are natural predators, so keep your small furry friends safe by housing them in an enclosure that cannot be opened by an agile paw. Keep them in a room that is off limits to your feline family member when not supervised.
Follow the same protocol with your feathered friends but be careful where you choose to keep them. Birds have some restrictions on where they can be kept for health reasons (not in direct sun or draft). Check with a veterinarian specializing in exotic pets if you have concerns on where to have your bird's enclosure.
Whether a bird or small mammal, you should make sure that their enclosures have adequate houses and boxes so they can escape from the cat's line of vision if they want to. It can be very stressful for any animal not to be able to escape the “evil eye.”
Following these guidelines and using your best judgement will help to ensure that your new feline family member and resident pets will come to live together in harmony.
If you have concerns for the health or behavior of your pets, immediately contact your local veterinarian.