Three baby mice took up residence in a small aquarium after the tragic Victor-ization of their mother. The plan was to keep them until they could be released into the wild, but their cuteness got the better of the plan.
The cage soon needed changing, but catching mice to transfer them is as hard as picking up drops of mercury with your fingers.
Habitrail (TM) would do the trick but it's pretty dear for temporary pets.
Soda bottles make a cheap and robust set of skyways and nesting chambers.
Step 1: Cut a hole in the mesh top.
A square hole, with diagonal cutters.
Smaller than the bottle top.
I cut at the corner to make butting two cages together, but the bottles can go anywhere.