Good luck with that. Keoki is 2 yrs old, Jazzy is 4. He is RELENTLESS in biting and pulling on her neck. He literally drags her across the room, and doesn't stop even when she yelps.
I've tried the squirt bottle, but it only works for that second that the squirt hits and then he grabs her again. Tried the clicker, but that only works for a second also before he's back on her.
So far, all that works for me at all is to physically stop him, make him sit/stay {which he is getting remarkably good at!} for several long minutes. Usually, once released he starts after her again, but then if I say "Keoki, STOP" or "Be nice" he will look at me sadly and then leave her…...usually. Sometimes he ignores me and goes after her anyway and then has to sit/stay again.
It's a constant...CONSTANT... battle that takes place many, many, many times every day.