They say that if you see one rat there are at least 20 more that you haven't seen.

One of my brothers lived at home with our parents; one day when I arrived there, he showed me a rat colony he had discovered under a couple of sheets of plywood.

I kid you not: There were withing hundreds of them under there, many of them still blind and hairless but other young old enough to explore curiously their suddenly bright world. The adults had all bolted.

I never asked him what he did with them; didn't really want to know.