How do I introduce another cat into my household?

Introducing a new cat into your home when you've already got one can sometimes be a difficult task.

Cats are social creatures, but they also enjoy having the option of being alone from time to time. You can see this if you get a chance to watch kittens raised in a litter together - they can become confrontational if they don't get their own space. By the time they're nine months to one year old, their play becomes more aggressive and a dominant hierarchy emerges in the group. Only then can they live together peacefully.
An adult cat who has been raised as the only cat in a household will probably display aggression when a new cat is brought into what she sees as her territory. However, most cats can learn to tolerate the presence of another cat - and some even become lifelong companions, sleeping and eating together, and using the same litter tray without any problems. The transition, however, may not always be easy. The secret is to make the transition as stress-free as possible for the cat who was there first.

Adult cats and kittens

If you've got an older cat, she may be more comfortable having a kitten - rather than another adult cat - introduced into her home. A kitten is not as likely to challenge the older cat over territory, and is more likely to submit to her dominance.

A quarantine period

The first thing to do is to keep your new cat in a separate part of your house for about a week. This is basically a quarantine period, which allows you to watch the new cat for signs of illness that might appear after the stress of moving to a new home has waned. By keeping the cats apart and providing separate food, water bowls and litter trays, you'll also minimise the spread of disease. Make sure your first cat's vaccinations are up-to-date and have your new cat examined by your vet as soon as possible, to make sure she's healthy and free of infections and parasites (such as fleas or intestinal worms). All of which you'd rather not have passed to your other cat. You should also talk to your vet about having your cat's blood tested for certain diseases such as feline leukaemia virus and feline immuno-deficiency virus. Neither of these diseases may be apparent at her examination, but both can be transmitted between cats in close contact. During this one week period, your cats can adjust to each other's smell and sounds, but at a safe distance. You'll also be able to judge how tolerant or intolerant your cats will be to each other when they meet face-to-face. Another important benefit is that the quarantine period allows the new cat to establish her own territory in a portion of the house. So be sure to choose your new cat's territory carefully - if your first cat loves to sleep on your bed at night, don't make your bedroom the new cat's territory.

Face-to-face

When you're ready to let the cats meet each other, start slowly. Let them meet through a gate in a doorway, for example. When they do meet face-to-face, expect lots of growling and hissing. As much as you can, try and let the two cats work things out on their own - but stand close by with a squirt bottle to spray in their faces with water, or a towel to throw between them if a serious fight does occur. Remember to give your first cat lots of praise and affection for good behaviour, and be understanding if this new roommate distresses her. Also, resist the temptation to pamper the new cat in front of her, in an attempt to protect it - she'll only resent the new cat for it.

What if they can't get along?

Occasionally, the two cats will continue to be aggressive long after the original introductions, and some cats will simply not adapt to life in a multi-cat household. If this is the case, you can always talk to your vet about dealing with these behavioural problems. Nevertheless, repeated aggressive attacks can endanger the health and mental wellbeing of the victim and the cats may need to be permanently separated. In most cases, with time and patience, two cats can learn to accept one another and live together in harmony. You may even come home one day and find two furry, warm bodies curled up together, purring quietly in peaceful contentment