A permaculture garden is a rat's paradise. Whether it be deep mulching, compost piles, hugelbeds or stacked firewood, rats love all of the above. If you were in an arid or semi-arid climate, removing sources of water makes a big difference.
Never keep food or water for pets or other animals on or near the ground, and never let it stay out overnight. Even controlling for that, if there are natural sources of food, like acorns or other nuts, fruits and berries, grass or weed seeds, etc., they will forage the same foods as squirrels and other rodents.
If denying access to food doesn't work, then the next logical step is removing shelter habitat. This would, unfortunately, require that you destroy your hugelbeds, make rodent-proof compost piles, remove deep mulch (perhaps replacing with a pebble mulch?), and put all firewood in rodent-proof racks.