We've used a ratzapper at home to dispose of a very large mouse population. None of the other tricks worked (removing food sources, etc.). We did manage to block most of the openings in our rubble foundation, and now just get one or two every fall.

The zapper is GREAT: fast and effective. It probably will work even at the zoo. I remember finding some sort of multi-story version for warehouse use when I was searching for a better mouse trap. Maybe that's what you need?