He does this no where else but the tub. Two nights ago he defecated in the tub up stairs and twice since then in the one down stairs. I keep him down stairs in the bathroom at night and sometimes during the day. I also put the litter box in the bathroom with a bowl of food and water. I'm not sure why hes doing this and I've even tried putting the litterbox inside of the tub. he still uses the tub even with it in there. I dont know if this has something to do with it but I took him in from outside because he was very skinny and looked untaken care of but he was also very tame so I suspect that he used to live in a house. I'm not sure how old he is because I havent taken him to a vet yet but I would say hes about half the size or maybe a little smaller than the smaller fully grown cats I own. thanks if anyone has any idea why hes doing this. I also have 3 other cats one male(5yrs) and two female(2yrs) which are a little smaller than the male. They dont get along with the kitten vry well.