How do animals keep themselves well in the wild? Folklore and traditional medicine have long laid claim to feats of self-medication by animals, but, until recently, scientists have dismissed such stories as romantic anthropomorphism. This is now changing as more and more scientists uncover examples of insects, birds and mammals self-medicating their ills. Chimpanzees carefully select bitter-tasting anti-parasitic plant 'medicines' that counter intestinal parasites, elephants roam miles to find the clay which counters dietary toxins, and many birds species line their nests with pungent medicinal leaves and so improve their chick's chances against the ravages of skin parasites. This book, the first general overview of the emerging science of 'zoopharmacognosy', explores the behavioural strategies animals use to maintain health by resorting to no more mystical an explanation than Darwinian selection. These strategies have successfully endured the ravages of natural selection and could provide a solid basis for improving the health of animals in our care. By observing wild health and the many similarities with human self-medication, we may even discover (or rediscover) ways to further improve our own health.