I've had two indoor cats for years and a few months ago I adopted a Holland lop rabbit. The transition for the cats has been fairly easy because we kept the bunny penned up unless we were around to keep an eye on things. About a week ago, the cats started to misbehave, and I realized that all of the events have been happening around the bunny's pen. They've started peeing in things around the bunny's cage (like their cat bed, my schoolbag, any shoes we keep lying around), and last night when we opened up the bunny's pen I caught one of them trying to use the bunny's litter box.
I know that change is difficult for cats, but we didn't have any problems until about a week ago. The cats haven't acted aggressive towards the rabbit at all (in fact, one of the cats runs away from the bunny), but I think they feel like the bunny is invading their territory which is why they think they need to mark the house around the bunny cage. How can I get them to stop?? I can't keep the rabbit penned up all day, but I don't want the cats to feel like I'm replacing them. Any advice would be appreciated.