Hi all! We've had our soon to be 6 month old kitten about 3 months now. We introduced him to our 2yo resident cat 'by the book' using the Jackson Galaxy method, and after about two weeks, they got along fine, she was happy playing, snoozing and grooming him and we gradually increased the time they spent together until he had run of the house and all has been well. About 2 weeks ago, Zelda, our big girl, started getting a bit hissy and bopping Buster if he played a bit too rough. He, obviously, has no off button and doesn't know when to stop and give her space and has definitely been stressing her out! I could understand the odd telling off, but She now hates being around him at all if she doesn't have to be and spends her days at the top of the cat tree or on the windowsill where he can't reach her yet! They have started having closer to 'proper' fights now, with growling and ears back, and Buster loves trying to ambush her and getting her to retaliate. She wouldn't really hurt him if she didn't 'have to,' but he is getting more antagonistic and refusing to back down if she warns him off so I'm worried about someone getting hurt if things don't change and she becomes less and less tolerant. I was wondering if this relentlessness could have anything to do with him reaching sexual maturity? He gets neutered on Friday and I'm planning on separating them and reintroducing them as if he is a new cat afterwards. She gets stressed when he smells of the vet anyway so I think a bit of a break would help their relationship. I do distract him when I catch Buster stalking her and he gets a lot of playtime with us, but it clearly does not compare to winding Zelda up! I don't want Buster to constantly be hissed at, as unphased by this as he seems, and I don't want Zelda to live feeling as stressed as she is. We have feliway friends plugged in and they have separate resources and enough litter trays and their own scratchers/high places/beds etc. I don't need them to be BFFs, but amicable aquaintances would be nice so I don't need to worry about anyone getting hurt when B gets bigger and stronger!