Some simple guidelines for observers to help identify "self-medication" in animals and how to proceed in the research.

Thus far a number of different types of evidence for zoopharmacognosy (auto-medication) have been accumulated. The following is an outline: (1). unusual feeding habits ((whole leaf swallowing i.e, Aspillia, Lippia, Commelinacea etc.; bitter pith chewing i.e. Vernonia amygdalina; bark, wood eating, see my review paper)), that do not seem to provide any nutritional benefit; (2) ethnomedicinal or pharmacological evidence of bioactive compounds in the plant suggesting a non-nutritional, perhaps, pharmacological effect; (3) indirect evidence for restricted use in certain habitats (hamadryas baboons in Ethiopia; Phillips-Conroy, 1986) or during certain seasons (Huffman, 1991; Kawabata & Nishida, 1991) where the risk of acquiring infectious diseases ((only parasites have been suggested thus far) are more likely than in other habitats or seasons; (4) evidence (behavioral, parasitological) for use at times of illness ((Huffman & Seifu, 1989); (5) followed by evidence for a positive pharmacological effect gained from its use at such a time (behavioral, parasitological: Huffman & Seifu, 1989; Huffman et al., 1993). It is no good to claim self-medication based on ethnomedicinal or pharmacological evidence of bioactive compounds alone. The most important thing to keep in mind, I think, is that no matter what the chemical content of the plant may be, you have to be sure that; 1. the bioactive compound(s) is present in adequate quantities in the plant part being used (e.g. thiarubrine A is not reliably found in the leaves of Aspilia: Page et al., 1992; Huffman et al., in press), 2. the animal does not have a detoxification mechanism to break down these secondary compounds, 3. the proposed pharmacological action is solidly based on ecological and behavioral parameters of the animal species in question, and 4. the use of a plant for a proposed effect can be directly connected with patterns of usage etc., suggesting either a cognitive or innate mechanism for which the continued use of the plant can be selected for.
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