Cats do not keep the mice away it is my belief that they preserve them for the chase.

Let take a cat, and foster her with milk And tender flesh, and make her couch of silk, And let her see a mouse go by the wall, Anon she leaveth milk and flesh, and all, And every dainty that is in that house, Such appetite hath she to eat the mouse. Lo, here hath kind her domination, And appetite banishes discretion.