Some animals have learned how to use plants to heal themselves
On an expedition early in his career, Michael Huffman was watching a group ol;'pnnf chimpanzees in an East African jungle when the primate researcher made a surprising observation. A mother chimp lay ill on a bed of branches in a tree as her two-year-old son climbed dangerously high. Too sick to scold or bring down her offspring, she simply ignored him.
A while later, the female chimp summoned the energy to climb to the ground. She then slowly ambled over to a shrub. Huffman watched as she removed several branches. After peeling back the bark, the chimp chewed on the inner pith. Next, she sucked out the juice.
From his research at Kyoto University in Inuyama, Japan, Huffman knew a lot about chimps and their behavior. He had never seen one of the primates sample or even show interest in this shrub before. So he asked his research assistant, Mohamedi Seifu Kalunde, what it was.
“Mjonso,” said Kalunde. A member of the local Tongwe tribe, Kalunde told Huffman the bitter-tasting shrub was medicinal. He explained that members of his tribe in Tanzania used it to treat stomachaches, malarial fevers and even gut infections caused by parasites.
Suddenly, Huffman recalls of that day in 1987, “I got really excited.” Huffman realized he just might have been the first university-trained scientist to watch an animal taking medicine. More specifically, he was likely the first scientist to realize the animal did so with an understanding that it was doctoring itself.
Over the following years, Huffman's follow-up observations revealed other chimps using the same shrub to cure themselves of ailments. Hisdiscovery has changed the way scientists study what animals eat, says Mark Hunter. He’s an ecologist at the University of Michigan in Ann Arbor.
“When we watch animals foraging for food in nature, we now have to ask, ‘Are they visiting the grocery store or are they visiting the pharmacy?’” explains Hunter.
Before his encounter with this sick chimp, Huffman had heard tales about animals self-medicating. As far as he knew, they were just that — stories. No one had confirmed a sick animal could seek out something it knew would relieve its discomfort or pain. Back then, most scientists thought only people knew enough to treat the sick with foods or other agents — medicines — to restore their health.
The day after he had watched the mama chimp suck out the mjonsojuice, Huffman grew even more convinced that she had been deliberately treating herself. She seemed to have made a full recovery. In fact, he and Kalunde had trouble following her as she sped through the jungle, slapping the ground and grunting when her son did not keep up.
Later, the chimp’s feces confirmed Huffman’s hunch. He had collected samples of her feces from both before and after she sucked out the juice from the branches of the mjonso plant.
In the dung the chimp had passed before eating the plant, Huffman counted 135 eggs from a common parasitic worm. The worm attacks the stomach wall, causing pain. He then examined what she had pooped out just 24 hours after eating the plant. That dung contained a mere 15 parasite eggs, or just 11 percent as many. The finding suggested the chimp deliberately ate themjonso to rid herself of a painful parasitic infection.
Over the years, Huffman would go on to witness other chimps eating mjonso and recovering within about a day. Evidence would show all had been infected with the same parasitic worm: Oesophagostomum stephanostomum (Es oh FAY go STOH mum STEF ah no STOH mum).
Any medicinal chemist would be wise to take note of such animal behavior, says Hunter, the ecologist. “We can learn a lot about how to treat parasites and disease by watching other animals,” he says.
Indeed, Huffman eventually worked with plant chemists to analyze what’s in mjonso. The shrub’s formal, scientific name isVernonia amygdalina (Ver NON ee ah Ah MIG dah LEE nah).…