BEHAVIORAL MECHANISMS OF SELECTION OF DIET COMPONENTS AND THEIR ECOLOGICAL IMPLICATIONS IN HERBIVOROUS MAMMALS

Theories of the evolution of diet-choice strategies in herbivores frequently assume complex mechanisms for the detection and selection of plant chemical components (''nutritional wisdom''). However, these mechanisms have yet to be demonstrated in the behavioral repertoire of herbivorous mammals. A review of the empirical and theoretical mechanisms of selection of diet components in herbivorous mammals suggests that these animals have constraints on their capacity to solve food-discrimination tasks, a finding incompatible with the idea of nutritional wisdom. As an alternative, a ''rule-of-thumb'' hypothesis is postulated. Rules of thumb are simple behavioral mechanisms that could theoretically provide mammalian herbivores with balanced diets without the need for postulating nutritional wisdom. Learning is thought to be the mechanism by which rules of thumb develop.