I'm am continuously having this problem with Max & Speckles. Speckles is bigger and declawed (she came to me already declawed) and is always being stalked by Max who is smaller but has claws. Max really doesn't like Speckles so I know it's not a play thing, he just likes to intimidate her. Poor Specks will get attacked when exiting from the litter box or if she's just trying to get from A to B. I tried the squirt bottle at first but then Max got used to it. So now, I do nothing and figure it's time for Specks to stand her ground. They are older now so it's not has bad as when I first adopted them 6 yrs ago.