So the little rats are copying the elder rats. Cute to see, until i noticed this:
One cage, where all the rats live, is open. The older ones can go in & out as they want. So they can have some rest to. They do that by jumping.
The little ones are copying this. They manage it, as tiny as they are, to jump high enough to get out. So, when i'm going to bed or it's evening, i put them in the only option I have here: a birdcage.
I know, it's small. But it's that or 8 kids running around!