Zoopharmacognosy: Nature’s Pharmacy Used by Animals

Zoopharmacognosy: Nature’s Pharmacy used by animals

Author’s name: Prof. Pradeep Mishra, Bhupesh C Semwal, Sonia SIngh*  

Introduction: Self-medicating behavior is a topic of rapidly growing interest to behaviorists, parasitologists, ethnobotanists, chemical ecologists, conservationists, and physicians.  Scientists from various disciplines are currently exploring the possibility that many species use plants, soils, insects, and fungi as ‘medicines’ in ways that guard against future illness (preventive medicine) and/or relieve unpleasant symptoms (curative or therapeutic medicine).  It is important to note that the scientific study of animal self-medication is not based on an assumption that animals possess an innate ‘wisdom’ by which they flawlessly know what is good for them.  Self-medication strategies are survival skills honed by natural selection.  In most cases self-medication could be motivated by a desire to immediately reduce unpleasant sensations.  Some species, particularly great apes, show an intention of purpose in their medication and in these cases the term ‘zoopharmacognosy’ was coined to describe the process by which wild animals select and use specific plants with medicinal properties for the treatment and prevention of disease1.

                  In other words we can say that, “Zoopharmacognosy” refers to the process by which animal self-medicate, by selecting and utilizing plants and soils and insects to treat and prevent disease. Coined by Dr.Eloy Rodriguez a biochemist and professor at Cornell University,  the word is derived from roots zoo (“animal”), pharma (“drug”), and gnosy (“knowing”)2. Since ancient times people have recorded observations of animals apparently healing themselves with natural medicines.  Many herbs still retain a common name that infers this use: dog-grass (Agropyron repens), catnip (Nepeta cataria), and horny goat weed (Epimedium sp.), to name a few.  However, these observations remain largely unexplored by science.  Many stories of animal self-medication are clearly designed to inform and communicate herbal lore rather than fact.  Others are simply misinterpretations of animal behaviour. 

                          According to Chinese folklore, many centuries ago a farmer in the Yunnan district found a snake near his hut. Fearful for his life, he beat it senseless with a hoe and left it for dead. A few days later, the same snake returned. Again he tried to kill it, but again it returned. After he had beaten it a third time, the farmer followed the severely wounded snake as it crawled into a clump of weeds, started feeding on them, and thereby rapidly cured the worst of its injuries. The plant in the story was Panex notoginseng, which now forms the main ingredient in the herbal formulation ‘Yunnan bai yao’, a white powder that cauterizes cuts and stems external bleeding immediately. It was standard issue in the Vietnam War, for use when soldiers were wounded far from conventional medical treatment1.

Self-medication by animals:                      

Chewing plants: Huffman is one of the pioneers of zoopharmacognosy, thanks to his observations in 1987 of an animal -the chimp – attempting to heal herself. Intrigued by her speedy recovery and curious about the cause of her illness, Huffman analyzed the chimp’s dung and found the intestinal parasite Oesophagostomum stephanostomumto is the most likely explanation for her symptoms. What’s more, he found lower levels of the worm in another female chimp’s excretions 20 hours after she ate the bitter pith from a Vernonia tree, when suffering from diarrhea. Huffman and his colleagues isolated an entirely new class of compounds from the pith, one of which, vernonioside B1, was found to possess antiparasitic, antitumor, and antibacterial properties.

                           Why chimpanzees go to all this trouble to find Aspilia leaves? For several reasons, scientists think that chimpanzees eat this plant to exploit its medicinal properties. First, chimps consume more of these leaves during the rainy season, when parasitic larvae abound and there is increased risk of infection. Second, swallowing the leaves whole rather than chewing they provide no nutritional benefit to the animals, as they pass through the animal undigested. Africans use Aspilia plant, for a wide variety of illnesses such as lumbago, sciatica, scurvy, malaria, and rheumatism.

                           Experts are now searching for answers to the bigger question: What is the mechanism by which leaf swallowing acts against parasites? One analysis showed Aspilia leaves to contain a bright red oil known as thiarubrine-A, a compound clinically proven to kill parasites, viruses, fungi, and bacteria. Huffman found live worms in chimp feces stuck “like Velcro” to leaf hairs and trapped within the folds. He speculates that worms may become attached to the leaves or somehow enticed into the folds during digestion, taking a “magic carpet ride” through the gastrointestinal tract, eventually to be excreted from the body. Chemicals in the plant may also decrease the ability of the parasites to adhere to the intestine, making it easier for them to be swept out by the leaves. To date, experts have documented 30 plant species whose hairy leaves are “swallowed whole,” not just by chimpanzees (Pan troglodytes), but by pygmy chimps, or “bonobos” (Pan paniscus), and eastern lowland gorillas (Gorilla gorilla graueri). These great apes, of course, share their forest pharmacy with another important primate: Homo sapiens. . Rubia cordifolia is the antiparasitic plant Ugandans use to relieve stomach ailments. Traditionally, people of that country also rely on Aneilema aequinoctiale for fevers, earaches, and to stop bleeding. Lippia plicata is ingested by Africans for more serious threats such as dysentery and malaria. And in Tanzania, Ficus exasperata is the preferred antidote for ulcer sufferers.

Wild remedies for reproduction: Animals may have “stumbled” upon a wealth of ways to control reproduction, and scientists believe recent discoveries are only the tip of the iceberg. According to World Wildlife Fund scientist Holly Dublin, African elephants (Loxodanta africana) seek a particular species of tree, possibly to induce labor. Dublin followed a pregnant elephant for more than a year in East Africa, and observed that the elephant followed a strictly uniform diet and pattern of daily behavior until near the end of gestation. At that time, the elephant walked 17 miles in one day -many more than her usual three- and ate a tree of the Boraginaceae family from leaves to trunk! Four days later she gave birth to a healthy calf. The University of Wisconsin anthropologist Karen Strier found that, at different times, muriqui monkeys (Brachyteles arachnoides)of Brazil go out of their way to eat leaves of Apulia leiocarpa and Platypodium elegans,and the fruit of Enterlobium contortisiliquim(monkey’s ear). The first two plants contain isoflavanoids which are componds similar to estrogen. Ingesting the leaves may increase estrogen levels in the body, thereby decreasing fertility. Alternatively, eating monkey’s ear may increase the monkey’s chances of becoming pregnant because the plant contains a precursor to progesterone (the “pregnancy hormone”) called stigmasterol.

Fur rubbing behavior: Mary Baker, an anthropologist at the University of California, studied that white-faced Capuchin monkeys ( Cebus capucinus) breaking open the fruits of certain species of Citrus plants, and rubbing the pulp and juice into their fur. They also tore stems, leaves, and seed pods from Clematis dioica, Piper marginatum and Sloanea terniflorastems, mixed with saliva and vigorously rubbed them in as well. These botanicals contain secondary compounds with healing and insect- repelling characteristics. Baker also observed that fur-rubbing behaviour becomes more frequent when temperatures and humidity rise during the rainy season. This may be due to the corresponding increase in the risk of bacterial or fungal infections. North American brown bears (Ursus arctos) chew the root of Ligusticum porteri, making a paste of the plant with saliva, rub on their faces. Ligusticum porteri contains coumarins- fragant organic compounds that may repel insects when topically applied3.                     

                            ‘Fur rubbing is a typical behaviour of rubbing masticated plant materials and other objects such as insects on the external surface of the body by animals. Fur rubbing has been reported in a variety of primates, like Cebus capucinus, C. olivaceus, C.paella, Atelos geoffroyi, A. belzebuth, Aotus boliviensis, A. lemurinus griseimembra, A. nancymaae and Eulemur macaco. It has been suggested that fur rubbing serves to repel or kill ectoparasites. In Venezuela, Capuchin monkeys rub highly toxic millipede secretion into their fur during the humid met season when insect bites are high. The millipede seretions contain benzoquinones, which are well known for their insect repellant property.White- nosed coatis (Nasus narica) have been observed coating their body with the resin of Trattinnickia aspera (Burseraceae). These may also serve to control ectoparasites and thus should be considered a self-medication4.

Eating bacteria for digestion: The folivorous, or leaf-eating, hoatzin, however, uses specialized bacteria in the crop to break down hard-to-digest leafy plant material. Research indicates that the bird’s gut bacteria also neutralize toxic secondary compounds found in the plants it eats.

Antimicrobial property of plant: According to biologist John Berry at Cornell University, sweet red fruits of Aframomum angustifolium, having antimicrobial properties actually pose a digestive threat to the normal, healthy population of microorganisms found in the gorilla’s gut. After eating fruits of this wild ginger, antibacterial compounds in the plant can temporarily damage these microbes, in turn upsetting the gorilla’s digestive system if they aren’t already a regular part of the diet. Evidence shows that the gorilla’s microbiota has developed resistance to the biologically active components of the plant in areas where it is commonly eaten–an adaptation3.

Anting behaviour: ‘Anting’ is a behaviour in which birds rub crushed ants throughout their plumage and some birds let the ants to crawl over their plumage by directly lying on ants nests. Anting is reported in more than 200 species of songbirds and it is used to soothe irritated skin, help with feather maintenance and repel or reduce ectoparasites. The most commonly used ants by birds for anting are those species which contain formic acid. Subsequent empirical studies with bird lice revealed that formic acid is harmful to feather lice.

Antimicrobial lining in the nests: The leaves of wild carrot (Daucus carota, Umbelliferae), significantly reduces the number of fowl mites (Orntithonysus sylviarum) in starling nests. The dusty-footed wood rats (Neotoma fuscipes) place bay foliage around their sleeping nests and it has been experimentally shown that the inclusion of bay foliage significantly reduces the flea larval survival. The wood ants, formica paralugubris often incorporate large quantities of solidified conifer resin into their nests. By creating resin-free and resin –rich experimental nests, it was demonstrated that the included resin inhibits the growth of pathogenic micro-organism inside ant nests4.

                         European starlings (Sturnus vulgaris), lining their nests with select fresh vegetation, these birds are protecting themselves from a myriad of possible infections. Wild carrot (Dauscus carota), for example, kills fowl mites in starling nests. The carrot contains the steroid B-sitosterol, a compound that repels mites and inhibits their egg-laying abilities. Wood storks also reuse old nests, often for generations, over many decades and also bring fresh green material to their nests.  Many of the plants they use are also highly volatile such as red cedar (Juniperus silicola), cypress (Taxodium distichium), black gum (Nyssa bioflora), poison ivy (Toxicodendron radicans), red maple (Acer rubrum), wax myrtle (Myrica cerifera), Virginia creeper (Parthenocissus quinquefolia), and water oak (Quercus virginiana). When tested against large skin beetles that infest wood storks, these plants had no effect.  However, wood storks’ selections show the same profile of aromatic, bitter and astringent plants, suggesting that medication may be about treating the symptoms of mites and bites rather than impacting directly on the ectoparasites.

                         The domestic house sparrow is in on the act too. In Calcutta, scientists have noticed that the house sparrow usually brings neem (Azidiachta indica) leaves, which are powerful insecticides, to line its nest at hatching time.  These sparrows have also been observed to change from neem to quinine-rich leaves of Krishnachua tree (Caesalpinia pulcherrima) during an outbreak of malaria. Quinine controls the symptoms of malaria and scientists wonder whether the sparrows were selecting leaves to deal with malarial symptoms1.

Consumption of soil: ‘Geophagy’ is an act of deliberately consuming soil, stones and rock by herbivorousand omnivorous mammals, birds, reptiles and insects. This behavoiur is observed and studied in the context of self-medication in Japanese macaques (macacca mulatta), mountain gorillas (gorilla gorilla), chimpanzees (pan troglodytes) and african elephants. Geophagy is suggested as a means to maintain gut pH, to meet nutritional requirements for traces minerals, to satisfy hunger for sodium to detoxify previously consumed plant secondary metabolites and to combat intestinal problems like diarrhea4.


                    Self-medication in animals remains a field with endless unexplored avenues. Washington University biologist Jane Phillips-Conroy, who studied self-medication in baboons, says, “Just because a monkey eats a particular plant doesn’t mean he knows it’s medicinal. We need more definitive studies like those of Huffman, with actual proof that particular plants are effective against particular illnesses. “According to Huffman, “With growing chemoresistance to the Western world’s current arsenal of antibiotics and anthelmintics [antiparasitics], we cannot afford to let that potential source of knowledge disappear3”. Actually, Zoopharmacognosy is based on the apparent ability of animals to show a cognitive grasp of potential medicines in their environment. Further new discoveries in the field of zoopharmacognosy is essential in order to teach us more about behavior, botany, and  with respect to medicine, all areas in which we may apply our knowledge to benefit the upcoming future generations.


  1. http://www.colostate.edu/Depts/Entomology
  2. http://en.wikipedia .org/
  3. http://nationalzoo.si.edu/publications
  4. Raman R and Kandula S. Zoopharmacognosy: Self-medication in wild animals. Resonance 2008: 245-53.

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