Why do bearded dragons scratch substrate?

If your bearded dragon is female and old enough, she might be trying to lay eggs. It's best that you have a separate digging box filled with substrate she can lay her eggs in, as substrates like sand, calci-sand, wood chippings, gravel, and other similar substrates can cause impaction.

However, your bearded dragon might also be trying to find a better basking or laying spot.