Zoopharmacognosy is a behaviour in which non-human animals use natural resources to self-medicate. The study of this fascinating phenomenon has the potential to impact a host of vital areas, from cancer treatment to sustainability. In this article, I will delve into the mechanisms, causes of and evidence for zoopharmacognosy, as well as how it is significant to humans.

Animal self-medication may be prophylactic (to prevent infection) or therapeutic (to treat infection or illness), and can be in the form of deglutition (swallowing whole), ingestion (chewing and swallowing) or topical application (whole or as pastes) of plants, soils and even insects with medicinal properties. Animals primarily use topical application to treat infections, wounds and pain, and repel insects. It is commonly done by chewing leaves and rubbing them onto fur or skin, releasing compounds that are analgesic (pain-relieving) or antibacterial. Additionally, some animals select plants with secondary metabolites (compounds produced by the plant that make them competitive in their own environment) that deter herbivores and insects from eating the plant so they can act as olfactory cues for insects to avoid the animals. Self-medication for anti-parasitic purposes is also common. Animals may do this by swallowing whole plants with trichomes (fine appendages on the plant surface) that can attach to parasites and dislodge them from the intestine. Alternatively, the material ingested may contain antiparasitic compounds like phytochemicals (chemicals produced by plants to help resist a variety of infections) which can decrease the ability of worms to attach to the lining of the intestine.

Certain criteria have been established for judging whether a behaviour displayed is truly an act of self-medication, allowing us to distinguish it from other behaviours like ordinary eating! Firstly, the plant must be intentionally sought out for its medicinal properties - it can not hold nutritional value or be part of the animal’s normal diet. Plants used preventatively against parasitic infection should be consumed during times of the year when parasites are more likely to cause infection, like the rainy season. Other animals in the group should not also participate in therapeutic behaviours. Additionally, there should be a plausible explanation as to why the substance has been selected (e.g. evidence of the medicinal properties and effects of the plant, and evidence of the effectiveness of the treatment).