Self-medication in Herbivores

Understanding Self-Medication in Herbivores

Project participant: Vanina Egea, Visiting Scientist IADIZA, Argentina

Virtually all plants contain plant secondary metabolites (PSMs). PSMs have long been recognized as defensive chemicals that deter animals from eating plants because PSMs are aversive and often have toxic effects. However, these same compounds can greatly benefit animal health if they are eaten at appropriate levels. For example, tannins – an important class of PSMs – can reduce intestinal parasites in ruminants. Herbivores are able to recognize this benefit and can form preferences for medicinal plants when they are sick; i.e., they self-medicate. The fact that sick animals may seek out and ingest PSMs simply adds another level of complexity to the diet selection of herbivores. Yet the mechanisms leading self-medication in sick animals are still unknown.

The overarching aim of this research is to understand what circumstances trigger self-medicative behavior in ruminants, and to gain insight into the connections between diet selection, parasitism, and PSMs.  We will test whether an increased level of parasitic infection is associated with an increased acceptance of novel foods and flavors. Herbivores may have evolved specific changes in diet selection in response to parasitism, which may result in them consuming appropriate doses of PSMs.