They are omnivorous. I've tried to get mine to eat anything under the sun and then some, but he's just not really a big eater. These are the only things he's really dug on, orange, worms, crickets. I've really tried everything.
I went to this really great vet who said that they should be eating more meat so I'm trying to get him to eat worms and crickets more than fruits and veggies.
He also told me that if I could get him to eat dog food that that would be ideal because then he'd be getting all his protein plus vitamins.
Hope this helps. As I said I'm still in experimental mode with mine. I did notice that he seems to like the crickets the most because they offer the added value of entertainment, but oftentimes he just maims them.