my new cat wont get along with other cats

Question
Hello,
I have had an old male cat for 6 years, a year ago we got a female kitten and they got along very well, the older cat was extremely friendly and the new kitten brought him happiness. a week ago we got a 1 year old female cat, she will chase our female cat all over the house, now she is being chased at her own house, the newer cat will make my other cat stay under the bed most of the day, she is afraid and is now using the bath sink as litter box since she will not go down stair to use it. On the other side, the new cat will not bother my older male cat because he will fight back.
what can I do to stop this?
thank you!

Answer
Hi
having two female,ale cats in the same house is not a good idea unless they were brought up together. the behavior is normal territorial aggression. The reason she doesn't go for the male is because he is not her competition the female is. remember cats are not pack animals and don't like to live in small areas with too many other cats.

How did you introduce the new cat to the the house? Also are all the animas neutered?

It is important that when bringing a new cat into the house that a strict introduction period is carried out see my page here /introducing-cats.html

However there are no guarantees that the situation will ever change, it may just calm down to where they just give each other the occasional swipe. There are no wonder cures I'm afraid, some cats get on some cats don't the problem is if it is making your other cats unhappy and nervous then you have to make a decision about whether or not it is fair to keep the new cat.

Best wishes
Kate