Feed him a fruit smoothie with some spinach in it. Do this a couple of days in a row. He’ll poop.
On a more serious note, it could be that his system cannot digest certain foods well. He could be lactose intolerant or gluten intolerant. It could be that he is eating the wrong foods. Too much soda, tea, cheese, refined foods and even Jello will cause problems. If the second is the issue, lot of water and lots of fresh fruit and veg are the answer.
I’m greatly amused by the fact that this thread picked up only 7 replies when first posted, but an additional 23 (including this one) since it was resurrected.
Hehe, I actually came in to comment, then saw something about ‘reanimating a zombie’ in one of the later posts.
Yes, I was scrolling through, 'cause lord knows I don’t really want to read about poop! I just saw the metamucil suggestion and came in to chime in that it’d be a good idea to avoid fiber-based laxatives unless there’s a LOT of water involved. Will make the problem worse.