Aggressive Play in a Previously Docile Cat

My cat is used to being around other cats and has always been playful and is immediately the submissive one when he is in a new home. However, that has just changed. We just moved into a new house and he plays well with the resident cat but most of the time they are in the same space but ignore each other. Yet, occasionally I have to tell them to "play nice" and have to clap my hands to get their attention on me, which usually the other cat takes the opportunity to run away. They have not broken skin (as far as I can see) but they hiss, growl, and puff up tails. My cat is always the dominant one and the other cat runs away or does the submissive pose.

The other cat has a heart disease and is de-clawed. Could those ailments be seen as a weakness and cause my cat to become the aggressive cat when before he was always playful and did not show a sign of aggression with any cat?

Any insights into the change of behavior?

Is there anything I can do to prevent this (causing tension with the housemate)?

Does the vanilla extract on the chin really work to make them not aggressive to each other?

Thanks

Vanilla extract is just used for introduction/reintroducing cats. It makes them smell the same but won't change who is dominate or who is submissive - cats have to work this out on their own.

It could be likely that your cat senses the other isn't strong enough to be dominate or maybe the other cat is more naturally a submissive cat. Moving into a new home can upset things a bit and sometimes the cats have to work out where they are now - both in home and rank.

Where they properly introduced to each other? or where they put together believing that your cat would be fine with the new arrangement. (Maybe he was, but the other cat may not have been as happy with it).

You could try reintroducing them properly if that was skipped. Make sure everyone is healthy and up to date on shots (if they need to be), never try to break up a scuffle with your hands/or any body part, and if you can keep your cat's claws trimmed to it may help even things out a bit. I'm assuming your cat is neutered too?

Stress and the other cat's heart disease may be a worry. If the cat has another owner you may wish to discuss that with them - if you've taken over care, it might be best to mention it to the vet.

My boys play rough with each other all the time. Neither is hurt but I often have to yell out "BOYS!" and clap my hands too when one gets carried away. It could simply be rough play and nothing more - Your cat may do that now be cause he knows he can.

They were properly introduced (at least I think). My cat stayed in my room for about 2 weeks and when they started communicating under the door regularly we let them out to see how they acted face to face. They ignored each other so we thought it was fine. Then they started playing at night/early morning but primarily ignore each other during the day. Which was a big change from my cat's normal behavior, which was eager to play all day with any kitty buddy.

A month after the introduction the fighting started. This is also around the same time the vet diagnosed the problem. At first I thought it was the vet smell, but for the last episode happened a few weeks after a vet visit. The first day they met was after the other cat returned from a check-up from the vet (the cats choice not ours).

There was another (much younger and smaller) cat before in the house and she was the dominate one. The other cat was always tensed around her. I heard that now the cat has relaxed and become more friendly since my cat moved into the house and the other cat moved out. My cat is very laid back and is friendly with all of the humans.

My cat used to be the submissive one around other cats even when they were in his territory.

These are both neutered males who are the same age and almost the same size.

I do not physically break them up so no worries there.

My cat is current with all his shots. The other cat I am not sure but now it goes to the vet often and most vets take care of that before they start subscribing medication.

Both of us take care of our own cats. We do not share any responsibilities (even while the other is away), litter, food, etc. And her cat is not as affectionate as mine so rarely does he lets me pet him even when he hangs out in my room.

Maybe it is play that escalates into aggression or perhaps my cat is trying to be dominate now after all of these years of being submissive. Or maybe he is just trying to force the other cat to be more playful with him like his other buddies were. Who knows what is going on in their heads but I wish they would stop it!

Have you tried using Feliway at all? That's pretty good for calming down cats and reducing aggressive behavior.