Some balls are just tempered "ill" and will occassionally bite for no reason. Other than that they will only bite out of defense or a feeding response. If you sneak up on him while he is resting he may strike. If your hand smells like food he may strike, or if he smells food and sees your hand moving he may strike. If you can sit around and hold yours he is probally not ill natured and you should be fine unless you do one of the last 2 things I mentioned.