Pet lost her owner

Question
Hi

We recently took in an 8 year old cat. Who only ever had 1 owner and only lived in one home for 8 years. We have 2 other cats that are just over a year old.  The new cat (Katie) is always hissing and growling at us, after we start talking to her. We just want to know the best way to introduce the new cat to our cats that we've had since they were born.  The new cat was my mother-in-laws cat so I seen it on a regular basis but we moved it to our place and just need to know how long the process should take for her to  get used to the new place and the new owners and also the new cats?  

Answer
Well, it sounds as though you may have gotten off on the wrong foot when you brought her in, but maybe it is fixable. I always recommend that a new cat be given its own space initially. In a multi cat environment, this is vital in helping it feel more secure and should be done before it interacts with the other cats. Do you have a spare room where you could confine her for awhile and give her extra attention while keeping the other cats away from her?
If so, I would do that for 3-4 days, and then put her into a carrier and start letting the other cats into "her" room for brief periods of time. If she is in the carrier they won't be able to attack her and she can hiss all she wants. After a couple of days of this I would switch to putting the other cats into carriers for a bit and letting her explore the house without having to have close interaction. If you follow this plan for about 10 days, and then let them interact again, you may see a reduced level of aggression and they may work out some sort of detente. I don't believe it will happen right now, though.

Another thing you may want to consider is taking the older cat to the vet. She is at an age where emotional trauma like this could spark physical symptoms and you don't want that to happen. It might make sense to consider some form of psychopharm medication -- this is becoming increasingly common with cats and is very effective in helping them get through difficult transitions like this.

Hope this gives you some useful ideas.

iris