By Sean Henahan, Access Excellence

ITHACA, NY (9/24/96) A bacteria-fighting fruit forms part of the regular diet of the mountain gorillas of Uganda. Now researchers are trying to determine if the animals use the fruit therapeutically, a process known as zoopharmacognosy.

"When you watch gorillas eat in habitats with wide plant diversity, you see why we say they're living in a salad bowl. They eat practically everything in reach -leaves, stems, bark, fruit -- and they barely move. When you come back the next day, they're eating a few meters away," noted Cornell University biologist John P. Berry, recently returned from a plant-collecting trip to the Bwindi National Park.

Working with trackers, who are hired to observe and protect the mountain gorillas, Berry has documented mountain gorillas eating more than 40 different types of plants.

"They eat some pretty unappealing stuff, too, like pith and rotten wood," said Berry, who has personally sampled much of the gorilla fare. "But so far I haven't found the kind of self-medication that we see in chimps and Aspilia," he said, referring to the first- and best-known example of zoopharmacognosy.

Eloy Rodriguez, now the Perkins Professor of Environmental Studies at Cornell, and Richard Wrangham of Harvard University, in 1985 showed that thiarubrine was the active chemical (against intestinal nematode parasites) in the Aspilia leaves that wild chimpanzees seek when they have upset stomachs. The queasy chimps pick Aspilia leaves and roll them around in their mouths, rather than chewing, before swallowing the capsule-like leaves whole. They swallow as many as 15-35 Aspilia leaves at a sitting, particularly in the rainy season when the rate of parasitic infection is highest.

Aspilia also may have some anti-bacterial effect, Berry, Rodriguez and Marcus McFerren noted in a 1995 article for the American Society of Plant Physiologists' publication, Phytochemicals and Health. When Berry found mountain gorillas eating fruit of the wild ginger plant called Aframomum, which has anti-bacterial properties, he wondered why.

The Aframomum fruits grow a few inches above the ground, on a plant whose distinctively shaped fronds reach 9 feet high. The bright red, sweet fruit of one Aframomum species is a favorite of Ugandan children and is sold in the marketplace and at roadside stands. The mountain gorillas eat the fruit along with their other salad items.

Back in his laboratory, Berry found that some species of Aframomum fruit prevent the growth of bacteria, including some strains of E. coli and Pseudomonas. He wondered if gorillas -- and human kids, too -are getting a does of medicine along with their sweets? If so, that might add another natural, plant-based treatment to the medicine chest.

But before prescribing Aframomum fruit for bacterial infection, Berry acknowledges that he must answer some basic questions:

"We need to get a better handle on the taxonomy and learn which species are growing where, which ones the gorillas are eating and which are eaten by humans," he said. "We need more tests of activity against pathogenic bacteria. I'd like to know how this fruit affects the gorillas' micro flora -- the 'good' digestive bacteria in their gut -- and whether their micro flora have developed a resistance to the fruit chemicals. And I have to get more information about the gorillas' feeding behavior."

One research technique might be bring a mountain gorilla into the Cornell phytochemical lab and serve him lunch, but that's not possible with one of the most endangered mammal species. The so-called Kyagurilu Group of mountain gorillas that Berry studies in the Bwindi National Park is down to just 13 individuals, including only one silverback (adult male) after deaths last year. But tests of the Aframomum fruit with lowland gorillas in American zoos may be possible, Berry hopes.

Taking field work to the extreme, Berry himself tastes almost everything he sees gorillas eat. He says that gorilla preferences cover a diverse range of tastes, from "sweet," "astringent" and "tasteless" to mouth-numbingly "bitter." However, some of the alkaloid-laden plants that gorillas crave, he notes, are poisonous to humans.

Safe of harm, mountain gorillas potentially have a life expectancy nearly equal to humans' -- 40 to 50 years -- and their health is generally good. What role their low-fat, extremely high-fiber diet plays in their health is another question for the phytochemists.