Exploitation of secondary metabolites by animals: A response to homeostatic challenges.

We propose that the exploitation of the bioactive properties of secondary metabolites (SMs) by animals can provide a "treatment" against various challenges that perturb homeostasis in animals. The unified theoretical framework for the exploitation of SMs by animals is based on a synthesis of research from a wide range of fields and although it is focused on providing generalized predictions for herbivores that exploit SMs of plants, predictions can be applied to understand the exploitation of SMs by many animals. In this review, we argue that the probability of SM exploitation is determined by the relative difference between the cost of a homeostatic challenge and the toxicity of the SM and we provide various predictions that can be made when considering behavior under a homeostatic perspective.

Tannins and self-medication: Implications for sustainable parasite control in herbivores.

Animals adapt to the variability of the external environment and to their changing internal needs not only by generating homeostatic physiological responses, but also by operating in the external environment. In this study, we determined whether sheep with a gastrointestinal parasite infection increased intake of a low-quality food containing a natural antiparasitic agent (tannins) relative to non-parasitized sheep. Four groups of lambs (n=8 lambs/group) were assigned to a 2 x 2 factorial design with parasitic burden (P=parasites; NP=no parasites) and the offer of a supplement containing tannins (yes, no) as the main factors.