Diet sampling by wild Norway rats offered several unfamiliar foods

The present experiment was undertaken to examine directly the diet sampling behavior of wild Norway rats (Rattus norvegicus) faced with a choice among familiar and unfamiliar foods. First-generation, laboratory-reared wild Norway rats ate from four food cups. Three of the food cups were in unfamiliar locations and contained unfamiliar foods. The remaining food cup was in a familiar location and contained a familiar food. Subjects in a control group were offered the familiar food in all four locations. We found (1) that subjects in experimental and control conditions took equal amounts of time to first visit food cups in unfamiliar locations, (2) that subjects in the experimental condition (those with access to unfamiliar foods) ate at unfamiliar locations at a slower rate than did subjects in the control condition (those with access only to familiar food), (3) that subjects in the experimental condition were no more likely than subjects in the control condition to eat at one unfamiliar location at a time, and (4) that following a bout of eating at an unfamiliar food cup, subjects in the experimental condition waited no longer than subjects in the control condition before eating from a different unfamiliar food cup. We interpreted these data as indicating that although wild Norway rats are hesitant to eat unfamiliar foods, once they begin to eat such foods, they do not sample among them so as to facilitate identification of any toxin present.