Is this strange cage behavior??

Question
My bearded dragon just recently has been running inside of his cage, climbing up on the glass to the point he's on his hind legs. He ends up getting sand on everything and all in his water and food bowls. As he does this is beard does turn black and usually he stops after about an hour or two. Why is he doing this and is there ANY way i can get him to stop so he doesn't keep wasting food??

Answer
Hunger, looking for a mate, chasing somthing that is actually outside the cage...  He doesn't understand glass so if he sees something he wants he goes for it, that is normal behavior.  You should also pile rocks in the corners so that he doesn't injury his spine by bending over backwards when he gets up on 2 legs.