We have a three-year-old Siamese male (Oscar), plus one of his female litter mates, plus an elderly female cat. Until three months ago, we also had an elderly male cat that Oscar was very fond of. Ever since that elderly cat died, Oscar has been pooping outside the box--something he NEVER did before he lost his friend. He's pooped in many different places, including the elderly cat's favorite sleeping places. He sometimes uses the box (we have four) and sometimes doesn't. I've read that this could be an expression of grief. Has anyone had a similar problem, and if so, what did you do to solve it?