Beardies don't sleep on the ground in the wild unless they have a place to hide or burrow, otherwise they could easily become a meal for a passing predator. I've had some of my dragons in the garden during the day and when the sun started to go down, they would climb up on a tree trunk or plant just a few inches to a foot off the ground. Its amazing how well they blend into their surroundings when they do this and I'm sure they do it for safety. Even in the house (my females free roam in their own room) they all find a place off the ground to perch at night, some on a shelf, in boxes, but rarely on the floor. You'll notice when you turn the lights out, your beardie will roam around to find a place to sleep, if they don't go under something, they end up against the side of the tank trying to climb upward. The lizards in the yard do it as well, if you go outside at night and look in the plants, they are all on a stem or a leaf perched off the ground. Even when you try to put a sleeping dragon down, it will almost always try to climb back up into your hand.