ABSTRACT
This chapter presents an overview of the nature of phytochemical defenses and the behavioral responses of animals to noxious foods. It aims to develop working hypotheses on the mechanisms that underlie an animal's decision whether or not to eat a poisonous plant. The chapter explores implications the working hypotheses have for future research and the management of livestock on rangelands that contain poisonous plants. An understanding of how animals might cope with plant defenses is important in developing management strategies to reduce livestock losses to poisonous plants. Phytochemicals are apparently of adaptive significance for plants in plant-abiotic, plant-plant, plant-pathogen, and plant-herbivore interactions. The chapter discusses empirical evidence for the existence of the mechanisms in diet selection by domestic livestock and develops working hypotheses to account for cases where livestock are poisoned from eating plants. The role of instinct in the recognition and avoidance of poisonous plants is problematical.
