Well I think others have summed it up pretty well, but as they said, as long as he doesn't show poor health I wouldn't worry too much. Two of of mine, Cleo and Jackson, both have a tendency to stay cool for whatever reason, and I have another one, Ace, who only ever seems to poop around shedding time. I think some of them just have their quirks. And as has also been mentioned, if he wants to get warm he can get there so long as there is a heat source. Even my hot natured ones will find the heated end once in a while, when they need it.