Is your dog old enough to be potty trained? Does he have anxiety when he is not with you? Where does he sleep at night? These are all factors that need to be considered when trying to figure out why he only poops at night. Probably what it comes down to is that he just can't hold it long enough to wait until the morning so you might have to adjust his feeding schedule so that he goes when you want him to go. I would try that first and then possibly you might just have to get up in the middle of the night to let him out.

Most dogs have bowel movements 15-30 minutes after they eat.

However, if they are eating things that are hard to digest, or used to being fed portions that are too large, the body ceases functioning this way.

Not able to ask a bunch of questions, I'd say try a few things, assuming a vet visit has ruled out anything medical:

1. Be sure you are feeding twice a day, and the evening meal is well in advance of bedtime.

2 Be sure your portion is reasonable for the dog. Should be enough to fill a stomach and no more, bearing in mind that dry food expands when wet (inside the dog) and that a dog's stomach is around the size of his cranium for small dogs or maybe a little larger for larger dogs. This also helps prevent gas and bloat.

3 Be sure the food is not extremely heavy in protein, and the dog is not getting foods that will cause constipation like cheese (dogs are lactose intolerant).

4. Movement helps stimulate the bowels, so if you have to walk your dog, make it a long walk or a FAST walk, about 20-30 minutes after the meal. If you have a yard, the dog may not want to go out alone in the dark, and may be rushing back in. Try going out there for a bit with him and seeing if the dog will play fetch or run around a bit to stimulate things.

5. Try walking your dog after the morning meal and praising the "potty" when you see it, and praising it when you see him doing it outdoors, even from a distance.

6. When you clean it up in the house, put it out in the yard, not in the trash. This tells the dog where you want it.

7. Your dog may be afraid to wake you up and tell you when he needs to go out in the middle of the night.

8. If all of the above does not work, back to basics with crate training.

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