Our cats Peter and Clem generally get along well, except Clem has taken to starting fights with Peter. He's almost twice as big and he's hurt Peter with a claw or tooth to the stomach that drew blood.
Our apartment has a long hallway with a bathroom in the middle that is the litter room with two covered litter boxes. When Peter uses the litter and Clem hears the scratching he'll wait outside the door to ambush him. If he catches Peter (usually right outside the bathroom) they'll become a ball of claws, teeth, fur and snarling. If he doesn't get Pether there he'll chase him and sometimes catche him and fight elsewhere. Peter's only defense is that he can jump to higher places in the apartment, but he has to make it to one of those locations.
Peter is fastidious in the litter room and spends a while cleaning up. He also grooms Clem a lot which is good as his eyes need it, but Clem puts up with that only for a short time and then swats at Peter. That usually doesn't lead to a full blown fight as Peter will generally stop once he gets swung at.
We've used medicine in the past which leaves Clem laying around in a daze, and we've used feeliway without affect. We've spoken to the vet and they recommend an animal behaviorist. We don't like using drugs, and don't have a spot in our apartment where another litter box could go. Any suggestions before we hire the expensive animal behaviorist?
And of course photos: Peter One Two
and Clem One Two