When It Comes to Wildlife That Self-Medicate, This Orangutan Isn’t Alone
In addition to Rakus, the Sumatran orangutan who healed his own wound, scientists have discovered scores of wildlife species that self-medicate with plants
- By Heidi Ridgley
- Wildlife Science
- Dec 18, 2024
To treat a wound under his eye (above), a Sumatran orangutan applied juice he had extracted from a vine. A month later, the wound had healed (below). European honey bees (bottom) use tree resin to prevent mite, viral and other infections.
LAST MAY, A SUMATRAN ORANGUTAN in Indonesia’s Gunung Leuser National Park grabbed headlines when researchers revealed he’d used a plant to heal a wound under his eye. The orangutan, known as Rakus, repeatedly treated his wound with juice he had extracted from the chewed leaves of a vine. He also used the solid part of the plant mash as a dressing, apparently to protect the wound from flies. The plant he selected, Fibraurea tinctoria, is recognized for its antibacterial and anti-inflammatory properties in humans. For Rakus, infection never set in, says Isabelle Laumer, a primatologist with the Max Planck Institute of Animal Behavior in Germany, and within five days, his wound closed. A month later, Rakus was completely healed, Laumer and her colleagues wrote in the journal Scientific Reports.
While theirs was the first published scientific study of a wild animal healing a wound through active self-treatment with a plant, researchers for decades have been reporting that myriad wildlife species—from great apes, elephants and bears to porcupines, birds and bees—possess an innate ability to find and ingest certain plants for medicine (or to use plants in novel ways) when they fall ill or when preventive measures make sense.
Most scientists studying self-medication focused first on big-brained primates, assuming that it takes some smarts to figure out how to use medicinal plants. “But insects are showing us that’s simply not the case,” says Emory University biologist Jaap de Roode. De Roode has discovered that if given a choice, monarch butterflies infected with a parasite that hampers their ability to fly will lay 68 percent of their eggs on milkweed with high cardenolide compounds. The same toxic chemicals that protect monarchs from predators, cardenolides also have antiparasitic powers. Mother monarchs seem to know how to give their offspring a fighting chance by laying eggs on what de Roode terms “medicinal milkweed.” When their caterpillars hatch and start eating the leaves, the larvae ingest the compounds that fend off parasites.
What researchers don’t yet understand is how animals develop such know-how. Some preventive and therapeutic adaptations are fairly new, including sparrows and finches that collect and line their nests with nicotine-laden cigarette butts to minimize mites. Others—such as elephants that use chewed leaves of Piliostigma thonningii to cure gastrointestinal upset and chimpanzees that fold and swallow rough leaves to purge parasites—are likely part of an eons-long evolutionary process, scientists say.
In some cases, a behavior can be the result of social learning—parents teaching offspring or newcomers sharing knowledge. It could also be a physiological response: The brain may alter behavior and taste preferences when an animal is sick based on messages from the gut, says Mike Huffman, a visiting researcher with the Institute of Tropical Medicine at Japan’s Nagasaki University and a founding biologist in the field of animal medication.
For Rakus, it might have come down to individual innovation, says Laumer, noting the great ape also had a wound inside his mouth. “He chose a plant that also has potent pain-relieving effects, so he may have gotten the idea to apply it externally after he noticed his mouth felt better,” she says. Or he accidentally could have touched his wound with plant juice, felt relief and decided to repeat the behavior. It’s also possible an unknown orangutan taught him the technique. Thirty-something years old, Rakus spent his first decades living outside the study area.
But in the end, it all comes down to genes, says de Roode. “You have to have inherited the gene that gives you the general ability to detect the right taste or smell in a plant for your needs,” he says. “With it, you can make the right response or decision, and it will allow you to pass those genes down to the next generation, because you’ve survived the infection.”
Thanks to human observation, animals are also passing such knowledge down to us and our future generations. That shouldn’t be surprising: Indigenous cultures have long looked to wildlife to learn healing and preventive practices. After observing chimpanzees using Vernonia amygdalina to treat intestinal parasites, for example, people across Africa began ingesting leaves of this shrub generations ago as a remedy for parasites, says Huffman.
Anticancer studies of V. amygdalina—commonly called bitter leaf—and two related plants show they also inhibit cell growth in breast, colon, prostate and skin cancer, including turning off mutant BRCA genes in people more prone to breast cancer. Other studies have found that compounds from various parts of the same plants can lower cholesterol, prevent blood clots, reduce fever and inflammation, stabilize blood sugar and alleviate stomach upsets.
Another possible wonder plant from West African rain forests—first noted by Gabon’s Babongo communities who observed its use by porcupines, chimpanzees and gorillas—is Tabernanthe iboga, used to make ibogaine, a drug that in low doses fights fatigue. Although ibogaine currently is illegal in the United States, Stanford Medicine researchers reported in Nature Medicine last January that it has potential to effectively treat traumatic brain injury and reduce PTSD.
In North America, Indigenous Peoples have developed a range of treatments based on observing animals—most notably bears. Black and brown bears seek out osha root, for example, which contains antiviral, antibacterial, antifungal and anti-inflammatory properties. Several Tribes use it medicinally. During the 1918 flu pandemic, Huffman says doctors reported that no one was dying of the disease on the Washoe reservation along the California–Nevada border, where osha root ingestion was practiced.
Understanding how wildlife use plant medicines can also improve the health of domestic and working animals. European honey bees, for instance, mix tree resin with wax to reduce infections from mites, bacteria and viruses. Beekeepers usually remove the sticky substance because it makes bee boxes hard to open. But when the boxes have grooved instead of smooth wooden boards, bees can deposit the mixture without it getting in the way, allowing them to protect their colonies against collapse.
“Animals know how to treat themselves, and the medicines they use remain effective much longer than the ones we make,” de Roode says. “Our pharmaceutical medicines isolate one chemical in a neat white pill. But plants have a whole mix of compounds, which makes it much harder for parasites, viruses and bacteria to evolve resistance.”
According to Huffman, the studies also serve as a reminder of how much humans need nature with all of its biodiversity. “The fewer species out there, the fewer teachers we have,” he says. “One thing I like about this research is it helps people appreciate what animals are doing for themselves, and how so much of what we do now with medicine, we learned from them.”
Heidi Ridgley is a wildlife, history and travel writer and editor based in Washington, D.C.
