Two Neutered Cats Fighting

Question
Hi,

I have two neutered Siamese cats. They're just over 1.5 year old, and are brothers who have been living with with me for the last 13 months now, without any major fights. (Both are neutered since 6 months, are not declawed and are not allowed outdoors).

A few weeks ago, we moved to a new house. The move was stressful on them, but not overly so. They settled in quickly and now accept this new house completely. A few days ago they saw a stray cat outdoors through a window. They were both angry/scared and fluffed up and growled at it. I threw water out the window and it vanished.

After this happened, things seemed normal. But since 2 days now, they two cats are fighting like crazy. It started one night suddenly. I came home late at night, and till then everyone says they were fine, but suddenly one of them started hissing at the other and backed off. The second cat chased the first one around the room, and I managed to separate them in different rooms. They spent the night separate (we tried to put them in the same room before sleeping but they just continued fighting). I've seen play fighting, and this was not that. This was all out crazy cat fighting, but neither got injured.

The next entire day we kept them separate. I tried to reintroduce them to each other, but they were still hissing so I put them in different rooms again. This is the third night, and while Tyler (the one who did the initial chasing) wants to let bygones be bygones, Charlie (the one who is doing the hissing now) refuses to let him near him.

I think Tyler maybe understands that Charlie is scared, since he enters the room every once in a while (they are in separate rooms anymore, and have been allowed to go around the house) he leaves as soon as Charlie hisses at him. Charlie refuses to leave my room (which is where they normally are) and looks really scared.

I don't know what to do. I know that Charlie will get over this, but how long? I can't have two litter boxes setup for them for weeks, so have decided to put them in the same room tonight and see how it goes, but I want to know why they're fighting like this. Should I take Charlie to the vet? Is he sick? (He looks fine, had his shots a week ago).

Answer
Nida,

What your cats did is not uncommon.  When they see a stray cat outside, their fight/flight/fright primitive reactions come into play and they forget who they are and who their friends are.  So, the natural human tendency is to separate them. This is exactly what you do not want to do.  I like to get them into a dark interior room of the household and let them "chill" in the dark until things settle down.  Cats have an intricate "getting to know you" ritual, and, when we humans interfere and separate the cats, we inadvertently prolong the whole business. Usually it takes a couple of days for things to return to normal and it is best to not separate the cats.  If it sounds line World War III, you just have to ignore it. No one is really going to get hurt (as you have already discovered) as it is mostly noise and posturing.

Leave them be and they will sort it out on their own terms.

Best reagrds... Norm.