Thank you for getting back to me. I'll start you out with a first aid measure that may help no matter what is wrong. Buy some Pedialyte (yes, the kind for human infants), and prepare a shallow warm bath consisting of 1/2 warm water and 1/2 Pedialyte. Soak your lizard for about 20 to 30 minutes. Since you think he may be constipated, after the first 10 minutes, with him still in the water, gently massage his underside from front to vent for an additional 10 minutes. That may be enough to help him pass some feces. Be sure to supervise closely. This should be repeated twice a day.
I would also collect a fresh sample of droppings and take it to a reptile vet to be checked for parasites. This link will take you to a directory of vets:http://www.anapsid.org/vets/index.html#vetlist
I do recommend that all new reptiles be examined by a vet shortly after purchase. Many of them have illnesses when they enter the pet store, so it's good to be cautious.
I would get rid of the walnut substrate. Despite the fact that loose substrates are recommended by pet stores, they are dangerous. They often cause impaction and constipation, and are the leading cause of eye infections. Reptile carpet or ceramic tile makes a better substrate. Here's a reputable site where you can read more about care:http://www.anapsid.org/savannah.html
If you have more questions, just let me know by clicking on REPLY. I hope your little one doesn't have anything seriously wrong.
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