Introducing a new cat to the household and especially your current cat should be done slowly. While some cats are very easy going and will get along with any other cats, the majority of cats find meeting another feline for the first time distressing and overwhelming.
First of all, please make sure your cats are neutered. This will prevent any added stress and hormones from hindering a good introduction.
We would suggest settling your new cat into one room of the house and apart from other cats in the household. When your new cat seems settled in his/her new environment, start swapping his/her toys, and a bed/blanket with some from the other cats. This will allow them to smell each other’s scent and familiarise themselves with it.
When you feel the new cat is ready to explore the rest of the house, swap the cats around so that the new cat can start to feel more confident in the rest of the house. Meanwhile, the other cat/s can be smelling items in the new cat’s room and familiarise themselves with that scent.
Next, you can try feeding the cats at the same time, at opposite sides of a door, so that they can smell and hear each other, but cannot see or get to each other.
When the cats all seem comfortable eating together at opposite sides of the door, you can think about cracking the door slightly, or using a baby gate. (if using a baby gate, position the food dishes so that they aren’t directly next to the gate, the cats will need some space)
If the cats don’t seem happy about this, go back to door closed with a small crack in it. These steps all take time, but patience is the key. And don’t forget to praise your cats for their good behaviour, but never scold for unwanted behaviour, this negative energy does not help any situation.
Face to face introductions
If feeding does go well, and you think the cats may be ready for introducing properly, make sure you play with all the cats first so they drain any excess energy before meeting.
Also, make sure there is plenty of space for the cats and they have escape routes if they want to get away from each other (i.e. cat trees, open doors, cat shelves).
At this point, don’t push things and if the atmosphere gets tense, separate the cats and repeat the next day. A good scenario would be for the cats to acknowledge then ignore each other, or smell each other and walk away.
Using a Feliway spray or diffuser can also help to lower stress levels, so it is worth trying this alongside the introduction.
The process of introducing a new cat takes time and patience and some cats will take longer than others, but even though they are solitary hunters by nature, they are social creatures and when introduced in the correct way, can live quite contently with each other.