I would put something in the cage for him to climb on, such as a sanitized piece of driftwood or cork bark.
Now that you mentioned it, The day before I went out to the park and got a nice 3 piece wood for him to climb. I ripped off the tree hide cleaned it with bleach and put it in the oven at 225 for about 30 minutes, Sanded it down for a smooth surface so it should be a nice little addition to his enclosure