I have a 16 yr old neutered male cat who does not always use the litter box. This behavior started a couple of months ago. Sometimes he uses it and sometimes he doesn't. There have been no changes to food or litter. It's like he doesn't know where the litter box is or he's just too lazy to go to it. I have been using Litter Attract which hasn't made any difference. Any suggestions? Would using some kind of deterrent spray help? He does this where there is carpeting, mainly living room and bedroom. Is he getting senile? If so, how do I deal with it? Other than this recent bad behavior, he is in good health.