I've always read that switching food sources could be a challenge, which is why I hadn't switched to rats. He's been eating mice since he was born and we got him as a teeny baby. When I received the new mice in the mail, they were so much bigger than the pet store f/t, I figured we'd be all set! If he doesn't begin to eat them again, I will definitely try rats, but given that I just got the order, I'd rather try and use them up first. I wouldn't, of course, compromise Dakota's health for the sake of frozen mice - but it would be nice not to waste the $$!!!