We have 3 cats as of now.. Cassa 10 years old, Demon who is 3 years old, and the newbie Twiggy who is going on 2. All are fixed Cassa is the first one we got and she was more a ppl cat. It took her 4 months to take to Demon when he was a kitten. Demon will not stop chasing Twiggy, he swats her, chases her to me it looks like he bullies her. He will sometimes growl and hiss as well. We keep Demon and Twiggy separate. Cassa and Twiggy are completely fine. We have tried redirecting with toys,feliway treats, he will eat his wet food in front of her but once shes done if she walks away he HAS TO BE THERE WITH HER! When shes in the bedroom on the "rotation" he will stay at the door or be at the door if we are in the bedroom. He even has a small tantrum if we put him in the bedroom and shes in the rest of the place. Any ideas on what to do?
I am not an educated expert, but this sounds like perfectly normal cat behaviour to me. As long as no cat is seriously hurt I would not worry to much. It's just their way of establishing a relationship, cats are not always gentle.
I know it's easier said than done, but try to intervene as little as possible. Instead try to give them room to figure it out for themselves, even literally in the sense of space to move. A narrow passage e.g. is always a problem.
If the cats are fighting, I thinks it's okay to step in between them, but it's better to give them a push and block their way then to grab them. But they will have to fight once in a while to determine who deserves the best place in the house or some other privilege.
Still I think it's hard to tell what goes on in their minds and hard to predict how their relationship will develope. I hope in time they will get used to each other and live in peace. Around my house there are two cats who are always avoiding each other and scaring each other away, exept when it's really cold, then they huddle together in a box that is hardly big enough for one cat.
Cats are territorial. Twiggy has invaded. You are right to keep them separated for some weeks, sometimes a couple of months. Letting them "work it out" without human supervision can be dangerous--especially with an older cat. Physical and psychological distress isn't good for anyone--kitties included.
Anytime I introduce new animals to each other, I let the new addition roam around in a contained area, like the kitchen with the door closed. The "resident" animal gets carried into the room and I hold them and reassure them they are safe.
Since they have already "met" I would just sit there and not let him attack or harass the newbie. Talk to him softly. Kinda like having a new baby with a toddler who is interested and then gets jealous when the new baby gets all your attention.
Good luck and please let us know how it's going with the new cat.