I am receiving 2 1 year old girls from someone who cannot keep them anymore they come with their cage and everything in it. me and my parents both agree that we will probably keep the new girls together and keep pretzel my old rat in her cage by herself. the question is do I still need to introduce them like I would a normal new rat even though they won't be living together? their cages will be right next to each other but a few inches away so there's no biting after a few weeks do you think it would be safe to let them free room together? Thanks!