I have a male gerbil I bought from the pet store a couple months ago, they are probably about 3 months old. My problem is one bites...HARD!! I don't think he's afriad, its not like he runs away from me. I'll put my hand in the cage, and he'll run up to me and bite it and he won't let go. He makes me bleed. the other one just nibbles a bit, and sometimes, I hardly realize hes doing it. He doesn't hurt his cagemate at all. I don't know what to do. Please help!!