We live in the countryside and happily alongside most of our natural neighbours, but every now and then we have a rat problem in the garden. We used to just top up the rat boxes with some poison for a few days and all would be sorted.
Now the poison is hard to buy locally and the supermarket stuff seems to have no affect, in fact it almost seems to attract them! I read online that a mix of one part bicarb, one part flour and two parts sugar can be affective. The theory being that it bungs them up.