Join Date: Mar 2010
Location: Maryland (DC area)
Unfortunately, no advice I can offer, only sympathy, from one who is in an uncannily similar situation at present.
I, too, have three males and a female--males 2-1/2, 1-1/2, and 9 months, and female 2 years. All neutered/spayed and in excellent health. One male, Blizzy, likes to go after the female, Snowby, and--unlike you--it took me five months to be able to leave them out together. Even so, once or twice a day Blizzy would go after Snowby. However, she was able to move about the main area of the house. I went away for four days over Thanksgiving, had a cat sitter for a half hour to an hour a day, she thought things went fine. But when I returned, Snowby would not come down from the counters or shelves, except for mealtimes. She won't even cross the foyer to use the litterbox--I have to bring it over to her now.
Despite my not having travelled the past six weeks, the situation is not getting better. Blizzy attacked Snowby again today. She is not unnerved otherwise, is still eating normally, but she rarely ventures down from the counters or tables and stays in two rooms of the house. I have tried treats together, as I used to, to no effect.
This is your thread and your problem, not mine, but since I have been experiencing something similar, I'd be very interested if anyone comes up with any good ideas. I have been silent here as to this problem because, frankly, I am at the end of my rope, as this follows a full year of trying to get them to tolerate each other peacefully--and without saying more, I have to admit, the situation has now reached the point where I have run out of behavior modification options.
So good luck in trying to nip this in the bud. I should add that I do break things up as soon as I see it happening or even brewing, and Blizzy knows from my behavior that I disapprove of his stalking her. He just can't seem to help himself.