They weren't good for much except amusing the children and keeping the rat population down.

Didn't they say that Paris had the biggest rat population in the world?

Only thing is, with the cats almost extinct, the rat population grew.

But this is hardly the city's first attempt to control the rat population.

The overpopulation of squirrels and a large rat population have been problems for the park.

He put the rat population of New York at about 250,000.

On the other hand, as noted above, the cats have thus far kept the rat population at bay.

Hatch is thought to have been a mongrel, and was brought on board to control the rat population.

The rat population hadn't increased, it was just that people saw more of them.

The defendant had allowed the rat population on his farm to grow too large.