Every cat I've ever had has been like this; if their litter box is full or for some other reason they don't want to use it, it's always the tub. I think it has

Every cat I've ever had has been like this; if their litter box is full or for some other reason they don't want to use it, it's always the tub. I think it has something to do with the relative privacy the high bathtub walls afford them.