3 Cats and my brand new puppy

Question
Here is the thing i used to have 6 cats 2 males and 4 females. I just recently got a puppy and have given away 3 of the 6 cats all that remains in the house are females. However the cats left behind used to get along now my oldest cat shibby hates my other cat bailey. They fight hiss growl at each other. But for some reason both bailey and shibby get along with my other cat Tika. I know there are some new scents in the house because of the puppy but why would 2 cats that used to get along suddenly hate each other. I dont understand it and i'm a little worried. Also bailey is pregnant.. so I'm not sure if that has something to do with it also. They dont really flip out about the puppy though. They swat and hiss when he get's too close but they dont go after him.What is going on here please help?

Answer
Hi
the cats are reacting to a number of things here. Firstly their home environment has changed quite dramatically, they have now got a puppy in their mists, which in itself can be quite stressful and take some time to get used to but also three of their cat companions have disappeared. SO now they will have great feelings of insecurities in their home environment and to try and come to terms with the changes cats may take out their stress on the nearest things, ie other cats, this is known as aggression trauma and occurs in all sorts of different stressful situations. Also if kittens are due this will also cause feelings of insecurity regarding territory and food, all very common.
There isn't much you can do yourself, basically the cats will have to sort out their new pecking order amongst themselves, this may take some time but is the natural way of things. All you can is to make sure that you do not scold your cats for their behavior as this may aggravate the situation, give them all that extra bit of attention during this transition time and also make sure that they have their own space away from each other and the puppy so that they have somewhere they can retreat to and feel safe.

Best wishes
Kate