Rat Patrol

Have just returned from a tour of duty with the Rat Patrol, an elite two-member corps of poorly-trained and squeamish rural denizens, on the look-out for vermin, of the worst sorts.
Armed with shovels, rakes, poison, a wheelbarrow, and that versatile household weapon -- a box of aluminum foil -- we have secured the perimeter, to the best of our knowledge.
However, our satisfaction with a job well done is tempered by the sinking feeling that we may have caused collateral damage, and a gang of chipmunks may now be now plotting a counterstrike.
Does anyone in the virtual world have a surefire, bottom-up, green solution to rats?
(Any jokes about politicians do not count.)
Over and out.