Rat and mouse activity is usually first noticed in the autumn when rats and mice are looking for a warm shelter where there is food available. Not surprisingly they will be searching for a comfortable garden shed, garage or outbuilding in which to bed down and survive the winter.
Look out for tell-tale droppings or greasy marks rodents make as they run in the dark along a wall. Traps are rarely successful in the long-term, you need to put down a bait that doesn’t arouse suspicion in the group and in sufficient quantity to control all the nest.