The Gorilla’s First-Aid Kit

By Cynthia Berger

Dr. John Berry holds a giant lobelia, a type of plant that gorillas will climb a mountain to eat. (Photos by Dr. John Berry, L.H. Bailey Hortorium, Cornell University, Ithaca, NY)

The Impenetrable Forest looks like its name—a solid wall of green. John Berry must crawl on all fours to get through the tangle of plants. A soft, low noise, like someone clearing his throat, filters through the leaves. It’s the sound of a mountain gorilla telling the others in her group, “Here I am.” Dr. Berry hears the sound of noisy chewing and smacking lips.

To the gorillas, the forest in Uganda’s Bwindi Impenetrable Forest National Park looks like one big salad bowl. Each morning, these gorillas roll from their leafy nests, wander a few feet away, plop down, and start eating. Just within reach are dozens of different plants.

These plants may also be healthful in another way. Some plants of the rain forest contain chemicals that are medicines—compounds that kill germs or parasites, or relieve aches or itches. Dr. Berry is here to see if gorillas can point the way to these useful plants.

Dr. Berry, a scientist at Cornell University, works with plant scientist Dr. Eloy Rodriguez. The two are “chemical prospectors.” Like gold miners panning through gravel, they sift and study the chemicals stored in plants, looking for compounds that may be helpful to humans.

A mountain gorilla munches on the fruit of the wild ginger plant.

Animal Pharmacists
It might seem strange to expect gorillas to lead scientists to new medicines. But other studies suggest that animals deliberately choose certain plants for their healthful properties. For example, chimpanzees pick young, fuzzy leaves from one plant and roll them around in their mouths before swallowing them whole. Scientists discovered that these leaves kill parasitic roundworms, which can cause a bellyache.

Rain forests like this one are good places for chemical prospectors to look for new medicines because so many different kinds of plants live in a single place. Unfortunately, some rain forests are disappearing fast. They need protection—and careful study.

Protecting the forest habitat is important for the animals that live there, too. Uganda’s Bwindi Park is home to three hundred mountain gorillas—about half of the world’s entire population of these endangered animals. The other half live in nearby Rwanda and the Democratic Republic of the Congo (formerly Zaire).

Gorilla Sounds
Each morning, expert trackers from Uganda’s National Park Service help Dr. Berry find the gorillas. “We all make the sounds the gorillas make—smacking our lips and grunting—so they’ll think we're just another bunch of gorillas,” Dr. Berry says.

The trackers use binoculars to see which plants the apes eat. After the gorillas move on, the trackers make a careful tour of feeding sites, looking for tooth-marks on leaves, bark, and stems.

Dr. Berry tastes everything the gorillas eat. He says that, unlike chimps, which eat mostly sweet foods, gorillas eat both sweet and bitter things. Dr. Berry’s favorite gorilla food is the fruit of a plant called Myrianthus. “They’re big and round, with yellow, stringy flesh, and they taste like pineapple. Pretty good!” he says.

On the other hand, he doesn’t care for the taste of rotten wood, but gorillas eat it with gusto.

Dr. Berry also collects samples of plants that gorillas eat. He dries them and takes them back to Cornell University to test their chemical properties. The field station in Uganda where he stays has no electricity and the air is cold and damp, so drying plants is tricky. He uses a special drying table with a wire-mesh top and a lamp underneath.

At Cornell, Dr. Berry grinds up the dry fruit or leaves and mixes them with water or alcohol to extract the chemicals. He puts little drops of the extract onto a flat round plate filled with a jelly-like food for microbes. Then he smears across the plate a sample of the kinds of microbes he wants to test. Finally, he leaves the plate in a warm place where the microbes can grow. If the extract kills the microbes or stops them from growing, it will leave a clear spot on the plate. Everywhere else the plate will be covered with colonies of microbes.

The Gorilla’s Diet
So far, Dr. Berry has counted seventy-one different kinds of plants on the gorilla menu. Three of these foods seem like possible sources of wild medicines.

One is the wild ginger plant. Nine feet tall, it has bright-red, sweet, finger-sized fruits. Another is Dombeya, which has edible bark. After examining gorilla droppings, the scientists concluded that the apes who eat either wild ginger fruits or Dombeya bark are not infected with bacteria.

A third promising plant is the giant lobelia. Dr. Berry says it looks like a plant that Dr. Seuss might have drawn: a crooked, fifteen-foot-tall stalk topped with clusters of bushy leaves. Gorillas sometimes make trips to a nearby mountaintop just to eat the roots and leaves. Dr. Berry thinks the plant may contain some helpful chemical.

It will take some time to test all the plants in the gorilla’s diet. But who knows? If the work of the chemical prospectors pans out, someday people may benefit from a rain-forest medicine taken from the gorilla’s first-aid kit.

All wild gorillas live in Africa. The small map shows the ranges of the mountain gorilla (green), the eastern lowland gorilla (purple), and the western lowland gorilla (orange). The big map shows the mountain gorilla’s two separate ranges in detail (also in green).