A Pharmacy in the Forest
When the annual American Association for the Advancement of Science meeting convened in Chicago this February, among the sessions was the first-ever symposium on zoopharmocognosy.
Like Dave Barry, I should pause here and assert: I am not making this up. Zoopharmocognosy is a word new to most dictionaries because it describes a new field of research--new enough so nonscientists haven't yet come up with some informal equivalent term. The scientists who coined the word put together Greek roots covering the items to be included, so that when they read "zoopharmocognosy," other scientists would understand they were dealing with the ability of animals to medicate themselves.
To anyone who's watched a cat eat grass to help upchuck a hairball, there's nothing extraordinary in the thought of animals taking natural medicines to make themselves healthy. What is extraordinary (and recent) is the recognition of just how sophisticated the process can be.
Primates are the champion drug finders. In Tanzania's Gombe National Park, anthropologist Richard Wrangham watched several chimps leave their group at dawn. While most of the chimps breakfasted on fruits growing near by, the wanderers hunted for 20 minutes to find a particular plant. They proceeded to pick its leaves and swallow them whole, wrinkling their noses as they did. Wrangham confirmed the reason for the wrinkled noses; after the chimps left, he swallowed some of the leaves himself. "It's extremely nasty to eat," he reported.
Wrangham sent leaf samples off for chemical analysis, and found that the chimps had good reason to tolerate the plant's terrible taste. The leaves contain a reddish oily substance that is deadly to fungus and many parasites, especially the little worm-like nematodes that particularly afflict chimpanzees. The Gombe apes had been taking antibiotics, and on an empty stomach to heighten the effect.
In another Tanzanian park, Primatologist Michael Huffmann watched a lethargic female chimp suck liquids from the pith of a certain shrub. Within a day, she perked up and seemed to feel better. When Huffmann spoke about his observation, local residents told him that people as well as apes used the bitter pith as a drug to treat diseases and parasites.
It seems impressive enough that people would ingest foul-tasting foods and figure out their benefits, much less that apes would. Possibly the people learned from watching the chimps, who are very consistent in their use of medicinal plants. Both Huffmann and Wrangham speculated that chimpanzees practice preventive as well as curative medicine, since apparently healthy animals would sometimes eat the foul-tasting antibiotic plants. The chimps engaged in this behavior more often during the rainy season, when they would be more susceptible to disease.
So far primates, cats, dogs, and bears have been included among the animals dosing themselves with vegetal cures. Monkeys may be engaging in the most subtle self-medication, at least according to the reports presented at the AAAS symposium. Karen Strier, a primatologist based at the University of Wisconsin, studies muriqui monkeys in
Brazil. She found that female muriquis apparently practice a form of chemical birth control. They eat leaves of a certain plant after giving birth; the leaves contain a substance that mimics estrogen, which would reduce their fertility. However, when they are ready to mate and produce offspring again, they seek out and eat a legume that produces a fertility-enhancing steroid.
The most surprising finding came from research on howler monkeys in Costa Rica, though the researcher--Duke University Primatologist Kenneth Glander--noted that he considers the findings only preliminary until more laboratory work is done. Glander found that female howler monkeys seemed to be altering the electrical potentials in their reproductive tracts by eating certain plants. The monkeys apparently were influencing the sex of their offspring by creating an environment favorable for male-producing sperm, which carry a negative electrical charge.
Actually, the most surprising finding may be that medicine is the oldest science, for apparently it is even older than humankind. Anyhow, that is the belief of what one might call the zoopharmocognoscienti...
