The quantity of food taken may also vary. What is certain, however, is that the actual losses caused are a multiple of their dietary requirements. Many workers have studied food preferences in attempts to find the 'perfect' bait. In terms of bait acceptance the most important variable is to lay the bait at a time when little food is available. In buildings this means making food as inaccessible as possible, which will be discussed later.
Most rats return to a fixed place of feeding.
There are two peaks of activity, the major peak occurring just after sunset and a minor peak just before sunrise. When hungry, or under crowded conditions, they may also be active during daylight hours. It is probably their ability to rapidly adapt their behaviour to new or changing situations, above all else, that has caused some rodent species to become major pests. This is most apparent in their reaction to 'new objects' placed in their environment by man. R. norvegicus is naturally very suspicious and tends to avoid any object that is new to it.