Big Boy Cat is a bully

[Seshat]

We have two cats, and a dog.

ElderlyCat is 15, has been with us all her life, and is becoming a bit fragile. She's also tiny.
Big Boy is at the prime of his life, and is almost as big as the dog.
LovingDog is playful, but also happy to snuggle.

When we got Big Boy, he and ElderlyCat soon sorted out that she was dominant, and that she didn't want to be involved in any of this playing business. They never really liked each other, but they realised that their humans wanted both of them in the house and they adapted.

We later got Loving, and Big Boy and Loving sometimes play with each other (and sometimes fail to understand each others' invitations to play).
Loving and Elderly have sorted things out, too. They both snuggle with me, or whichever other humans are around, and sometimes they'll snuggle with each other.

So far so good.

Elderly is now becoming more frail, and Big Boy has realised that he's tougher than she is. And has decided it's fun to pounce on her.
He doesn't do anything else - just pounces then runs off - but it's enough that Elderly Cat hates it.

This morning, when I sat down at my computer, Elderly came to her favourite sitting spot on my lap, and was looking around and acting like she was terrified. She'd scan around at each of Big Boy's favourite pouncing spots. He was in clear sight of her, and well away from her, but it didn't matter - she was still scared.

We've tried playing with Big Boy. We've tried disciplining him whenever we see him pounce her. We've tried encouraging his play with Loving Dog.

Does anyone have any ideas? We may have to rehome him until Elderly Cat dies, and we accept that. But other ideas are welcomed.

[AriGriffin]

Smudge likes to pounce on Molly and then high tail it out of there. I've taken to squirting him with a water gun when I can tell he is getting ready to pounce. Most of the time it works. Do you have a spare room you can keep him in for a bit? I've put Smudge in the bathroom for a bit before when he got too pouncy as sort of a time out. He goes in the bathroom when I'm not around to supervise. I rarely catch him trying to pounce on Molly. She got the same treatment (squirt of water), when I saw her try to pounce on him.

[TheMike]

ditto on the water gun (just a cheap little hand one) enough to give him a shock works well if you can catch him mid pounce or immediately after.

[Seshat]

We've tried time outs. We've tried discipline (Voice, hand, and squirt gun). No luck.

[Andara Bledin]

With squirt guns, you can put a little lemon in it to make it more irritating.

Unfortunately, you're dealing with a domination play, and there's likely not a lot you can do about it, other than to keep them separated. It sucks but with the boy knowing that he can do a domination play and become house alpha (of the pets), he's going to take it. You could try to establish that you're above him and don't approve, but with cats that tends to have mixed results.

We're likely going to have to deal with something similar when our 15+ year old queen finally starts slowing down. Our 2 year old boy has been testing her pretty much weekly for a year, so it won't get better. Though with the kitten in the house, he's got some competition for most rambunctious.

^-.-^

[Seshat]

I think we're going to close up a patio area in the back yard, and shut the boy in there until Elderly Cat dies.

He'll love being where he can watch pigeons and the like. She'll enjoy the heated, safe space.