So I just had an epiphany that when my first rat passes on, (which won't be for awhile, but I worry about it anyway...) my other rat will likely live for quite a bit longer, as she is quite a bit younger. The younger rat is very dependent on the older one, because she's very skittish and I think she thinks the older girl will protect her. When I take Topsy out of the cage, Heide will barely move, and when I bring her back she perks right up. So I worry that when Topsy passes, Heide will constantly be in the state she goes into when I take Topsy away. So what should I do? It seems to me like a good solution would be to introduce a rat her own age, but I'm not sure she'll form the same bond as she has with my current girl. I don't want her to be all alone, though. Is it better to have her by herself, or to introduce her to a new friend?