Bark Eating Ambanja

[Solomon]

I've noticed my male Ambanja eating the bark off some of the branches in his cage and also eating the dead crunchy leaves.
I'm wondering if he may be lacking something in his diet?

I breed meal/superworms and gutload everything with the recipe on the Adcham website. He also gets silkies and waxworms when I have them. Twice a week he gets calcium D3 and twice a week a mulitvitamin dusting.

He's still eating his bugs like a champ - I'm really beginning to wonder why he's doing this? Any ideas?