The impact of plant secondary compounds on primate feeding behavior

Abstract

Primates, Secondary compounds, Feeding behavior, Nutrients, ABSTRACT The recent literature on plant secondary compounds and their influence on primate feeding behavior is reviewed. Many studies of nonhuman primates document the extreme selectivity that primates, particularly herbivo- rous species, demonstrate in their food choice. Until quite recently investigators interpreted this to mean that herbivorous primates were not food limited. This view has been challenged in the past 10 years by researchers concentrating on the primate-plant interaction. Chemical analyses have demonstrated that plant parts are of varying quality due to differences in nutrient and secondary compound content. The assumption that all leaves (or fruits, flowers, and insects) are po- tential foods of equal value to the primates eating them is refuted. The observed selectivity and preferences of primates for specific plant or insect species and parts are now viewed as strategies for dealing with the nutrient and secondary compound content variation in these foods. The field of plant-herbivore interaction is a rapidly expanding one that includes the phytochemical relationship between plants and herbivores. It has long been acknowl- edged that plants and insects profoundly influenced each others' evolutionary courses, but only recently have the biological and ecological roles of plant-produced secondary compounds been recognized. Stahl (1888) was the first to suggest that plants use chemical defenses in addition to the more familiar morphological and mechanical means of protecting themselves. Despite this early observation, plant produced chemicals were considered nothing more than waste products of plant metabolism until Fraenkel (1959) again suggested a defensive function for these compounds. Since then impressive evidence, which dem- onstrates that plants do use secondary compounds for defensive purposes, has accu- mulated (Ehrlich and Raven, 1965; Feeny, 1968; Janzen, 1969; Fthoades and Cates, 1976; Rosenthal and Janzen, 1979; and included references). Mothes (1976) went so far to suggest that secondary substances may be primarily defensive in nature and are neither essential nor of any physiological importance to the plants that produce them. He stated that the loss of these chemicals does not reduce the plant's viability.