Animals medicate themselves with plants – a behavior that has been observed and imitated by humans for thousands of years

When a wild orangutan in Sumatra recently suffered a facial wound, apparently after fighting with another man, it did something that caught the attention of the scientists watching.

The animal chewed the leaves of a liana vine – a plant that apes don’t normally eat. Over several days, the orangutan carefully applied the juice to his wound, then covered it with a paste of chewed liana. The wound healed with only a weak scar. The tropical plant he chose has antibacterial and antioxidant properties and is known to relieve pain, fever, bleeding and inflammation.

It was the media around the world that broke the story. In interviews and in their research paper, the scientists said this is “the first systematically documented case of active wound treatment in a wild animal” with a biologically active plant. The discovery will provide “new insights into the basis of human wound care.”

left: four leaves near ruler.  right: an orangutan in a treetop

For me, the behavior of the orangutan was familiar. As a historian of ancient science investigating what the Greeks and Romans knew about plants and animals, I was reminded of similar cases reported by Aristotle, Pliny the Elder, Aelian and other naturalists from antiquity. A substantial body of accounts from antiquity to the middle ages describes self-medication by many different animals. The animals used plants to treat illnesses, get rid of parasites, neutralize poisons and heal wounds.

The term zoopharmacognosy – “knowledge of animal medicine” – was coined in 1987. But as the Roman natural historian Pliny pointed out 2,000 years ago, many animals have made medical discoveries useful to humans. In fact, indigenous peoples and cultures of the past discovered a large number of medicinal plants used in modern drugs that saw animals using plants and imitated them.

What you can learn by watching animals

Some of the earliest written examples of animal medicinals can be found in Aristotle’s “History of Animals” from the fourth century BCE, such as the well-known practice of eating grass when dogs were ill, probably for cleansing and deworming.

Aristotle also noted that bears look for wild garlic as their first food after winter. It is rich in vitamin C, iron and magnesium, a healthy nutrient after the long winter’s sleep. The Latin name reflects this country’s belief: Allium ursinum translates to “lily bear,” and the common name in many other languages ​​refers to Bears.

medieval image of an ox being wounded by a hunter's arrow, and the other is also wounded, but eats the black herb, causing the arrow to come outmedieval image of an ox being wounded by a hunter's arrow, and the other is also wounded, but eats the black herb, causing the arrow to come out

Pliny explained how the use of dittany, also known as wild oregano, to treat arrow wounds arose from watching wounded oxen grazing on the herb. Aristotle and Dioscorides credited wild goats with the discovery. Vergil, Cicero, Plutarch, Solinus, Celsus and Galen claimed that dittany has the ability to dislodge an arrowhead and close the wound. Dittany’s many known phytochemical properties include antiseptic, anti-inflammatory and coagulant effects.

According to Pliny, deer also knew an antidote for toxic plants: wild artichokes. The leaves relieve nausea and stomach cramps and protect the liver. To cure spider bites, Pliny wrote, deer ate crabs washed up on the beach, and sick goats did the same. In particular, crab shells contain chitosan, which supports the immune system.

When elephants accidentally swallowed chameleons hiding on green foliage, they ate olive leaves, a natural antibiotic to combat salmonella that was being fed by lizards. Pliny said that ravens eat chameleons, but then ingest bay leaves to combat the lizards’ toxicity. Antibacterial bay leaves relieve diarrhea and gastrointestinal distress. Pliny noted that the black flounder, the partridge, the coot and the pigeon eat bay leaves for digestive problems.

17th century etching of an easel and basilisk in conflict17th century etching of an easel and basilisk in conflict

The rue was said to be an evergreen plant to combat wounds and snakes. Fresh rue is toxic. Its medicinal value is unclear, but the dried plant is included in many traditional folk remedies. Swallows collect another toxic plant, celandine, to make a bird for the eyes of their chicks. Snakes emerging from winter remember their eyes on fennel. Fennel bulbs contain compounds that promote tissue repair and immunity.

According to the naturalist Aelian, who lived in the third century BCE, the Egyptians traced much of their medical knowledge to the wisdom of animals. Aelian described elephants treating spear wounds with olive flowers and oil. He also mentioned cockroaches, partridges and turtles crushing oregano leaves and applying the paste to wounds.

The study of animal medicines continued in the Middle Ages. An example from the 12th century English compendium of animal lore, the Aberdeen Bestiary, tells of bears dressing wounds with mullein. Folk medicine prescribes this flowering plant to relieve pain and heal burns and wounds, thanks to its anti-inflammatory chemicals.

Ibn al-Durayhim’s 14th-century manuscript “The Uses of Animals” reported that swallows cured eyes engorged with turmeric, another anti-inflammatory. He also noted that wild goats chew and apply sphagnum moss to wounds, just as the Sumatran orangutan did with liana. Sphagnum moss dressings neutralize the bacteria and resist infection.

Nature’s pharmacopoeia

Of course, these pre-modern observations were folk knowledge, not formal science. But the stories reveal long-term observation and imitation of different animal species self-medicating with bioactive plants. Just as traditional Native ethnobotany is at the forefront of lifesaving drugs today, scientific testing of the ancient and medieval claims could discover new therapeutic plants.

Animal self-medication is now a rapidly growing scientific discipline. Observers report sightings of animals, from birds and rats to porcupines and chimpanzees, deliberately using a considerable store of medicinal substances. One wonder is that finches and sparrows collect cigarette butts. The nicotine kills mites in bird nests. Some vets even allow sick dogs, horses and other domestic animals to choose their own prescription by sniffing different botanical compounds.

A mystery remains. No one knows how animals sense which plants cure illness, heal wounds, repel parasites or otherwise promote health. Are they responding deliberately to specific health crises? And how is their knowledge transmitted? What we do know is that people have been learning the secrets of medicine by watching animals self-medicate for thousands of years.

This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. Written by: Adrienne Mayor, Stanford University

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Mayor Adrienne does not work for, consult with, share in, or be funded by any company or organization that would benefit from this article, nor has she disclosed any material interests beyond their academic appointment.

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