African Apes and Ethnomedicine
Convincing evidence for self-medication in wild chimpanzees has accumulated
over the past 25 years or so. Observations have identified self-treatment
for parasitosis and related illnesses through leaf-swallowing and bitter
pith chewing, and it has been discovered that plants used by the apes
are identical to those used by local human populations for their own medications.
Michael Huffman of Kyoto University has demonstrated that the leaves of
five different species of plants are employed by chimpanzees to reduce
parasite loads. The common factor in all of these leaves is their abrasiveness.
Swallowed whole, they scour parasites from the gut wall and are then passed
through the animal with the parasite hooked into the leaf.
Deparasitisation via a chemical process is believed to occur when chimpanzees
chew the stems of some plants. One of these, Vernonia amygdalina,
has been extensively studied and has been shown to possess antischistosomal,
antiamoebal, antileishmanial and antispasmodial properties. The Watongue
people of the Mahale Mountain region in Tanzania utilize this plant for
the treatment of parasitosis and gastrointestinal upsets, the rate of
recovery being 20-24 hours for both man and chimpanzee.
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Pygmy chimpanzees or bonobos of the Lilungu-Lokofe region of the Democratic
Republic of the Congo utilize Rauwolfia vomitoria, Manniophyton
fulvum, Tabernaemontana crassa, Scorodophloeus zenkeri,
Megaphrynium macrostachyum and Bellucia oxinanthera: all
the medicinal plants used by the Mbuti and Mongo-Boyela peoples of the
area.
Common chimpanzees living in the Bossou region of Republic of Guinea in
West Africa are known to exploit the leaves of two medicinal plant species:
Ficus mucuso and Polycephalium capitum. Complete leaves
have been found in chimpanzee faeces, and Polycephalium is used
by local people for the treatment of diarrhoea. Chimpanzee populations
in the neighbouring country Ivory Coast also swallow the whole leaves
of this plant, while in the Kahuzi-Biega area, Democratic Republic of
the Congo, both chimpanzees and gorillas swallow whole the leaves of the
herb Commelina cecilae.
The similarities in the use of plants by man and apes is highlighted by
the employment of leaves of Hypophrynium braunianum. The chimpanzees
of Bossou break off a leaf, put it into their mouth with one hand, fold
it on the roof of their mouth, take it out, insert it into a hole in the
base in a tree, then put back the folded leaf with the water into the
mouth. Significantly, this leaf is also used by local people when they
drink from small streams, although humans make a cup from the leaf instead
of folding it.
The chimpanzees of Gombe National Park and the gorillas of Bwindi National
Park have both suffered from outbreaks of scabies in the past, all contracted
from humans or livestock. Both ape populations had to be treated via human
intervention, but in some regions there are reports of chimpanzees self-medicating
against skin complaints. The Mende people of West Africa gain knowledge
of herbal medicine by observing wild chimpanzees that are sick. A forestry
worker observed a chimpanzee chew up a certain leaf and spit it onto the
affected area of skin. When he later tested it on himself, the observer
found that it was effective against skin irritations. A similar case was
recorded in the 1920s when an English woman was travelling through Liberia
and was told by an old local woman that she had watched a female chimpanzee
treat her infant's skin complaint with some large flat leaves that she
had crushed and pounded between her fingers and applied them to the baby's
infected area. The old woman later found these leaves to have curative
properties.
Although observations of self-medication in gorillas is meagre, these
great apes must also benefit from phytochemicals which inhibit certain
pathogens. In Mgahinga Gorilla National Park, Ugandan gorillas share a
number of the same medicinal plants with humans. Park wardens have noted
that 35 plant species form the core diet of gorillas in this region, and
that several of them are also medicinal plants. The bark of one of these,
Dombeya quinqueseta, is used to combat diarrhoea, and analysis
has identified a mixture of fatty acids (including palmitic, stearic,
linoleic and linolenic) and phytosterols (including beta-sitosterol).
These compounds are potent antimicrobials. Other gorilla foods from this
area found to possess active medicinal properties are Rubus rigidus
and Brillantaisia kirungae. Local medicine men watch what gorillas
and other animals do when sick to discover herbal treatments.
Jessica Rothman of Cornell University researching gorilla diets in neighbouring
Bwindi National Park found that local people employ 22 plants ethnobotanically,
and that some of these are also ingested by gorillas; the same plant parts
are exploited by the apes as are used medicinally by humans. They include
Rytigynia kigiensis, the rotten wood of which is used by locals
to make into a drink to treat worms and intestinal problems; Ocotea
usambarensis, whose bark, wood, rotten wood and leaves are used to
alleviate conditions associated with parasites; Vernonia spp., of which
the whole leaves of different species are employed as a drink for worms
and intestinal complaints; and Rubus spp., the young stems being
mixed in warm water and given to infants for colic. A few species of wood/rotten
wood consumed by gorillas are used locally in preparations for intestinal
parasites: Sesbania sesban, Maytenus spp. and Myrica
spp.
The use of rotten wood medicinally could be significant. Decaying plants
are broken down by saprophytes (fungi and bacteria), which release the
nitrates from the proteins. One of the most important products of this
decay is ammonia which, when taken orally in small doses, acts as a rapid
and diffusable stimulant, acting on the heart, respiratory system, and
on the bowel wall. In medicine it is usually given to those colics which
are due to an atonic condition of the intestinal wall, resulting in overloading
or stoppage, when its stimulating effect on sluggish bowel movements is
well noted.
The Bwindi gorillas also frequently use a cyanogenic bracken fern for
nesting material, and local people employ these plants as insect repellents.
A primary source of food in the diets of gorillas and chimpanzees in many
regions is the wild ginger Aframomum. Current research indicates
that there are about 80 species throughout Africa, approximately 40 of
these being found in the Cameroon-Gabon area. The most preferred species
appears to be A. angustifolium (also known as A. sanguineum),
being exploited by gorillas in at least seven distinct and widely separated
regions. The few species of Aframomum that have undergone bioassays
have revealed a broad spectrum of antiparasitic, antibacterial, antifungal
and antiviral properties, and it may well prove that these plants not
only furnish apes with nourishment, but also provide them with a source
of preventative medicine. John Berry of Cornell University has established
that citric acid accumulated in the fruits of A. angustifolium
act as an antimicrobial principle.
In a paper in African Study Monographs (2002) on the medicinal
properties in the diets of gorillas, Michael Huffman and I suggest that
gorillas may have a penchant for plants bearing caffeine and theobromine,
particularly the so-called "nuts" of cola trees. The seeds of
these fruits usually contain 2-2.5% caffeine and theobromine, both stimulants,
and in some areas gorillas are very fond of these seeds. Gorillas, especially
adult males, are large primates that have been found to frequently climb
very high trees during fruiting seasons in lowland rainforests. In montane
regions they traverse steep slopes in oxygenthin atmospheres, and it is
not difficult to surmise that under both of these environmental conditions,
cardiac stimulants would not only be desirable, but also adaptive. The
importance of certain compounds and alkaloids in natural gorilla diets
is emphasized by mortality rates in captive gorillas, where poor diets
may be a contributory factor. A survey in 1997 of diseases in gorillas
in North American institutions revealed that 41% of females aged seven
years and over, and males aged nine years and over, died from cardiovascular
disease.
Zoopharmacognosy (the use of medicinal plants by animals) is a science
still in its infancy, and new data is being gleaned only slowly. So far,
the plants that have been identified and pharmacologically screened barely
scratch the surface. Many more plants, particularly in the world's rainforests,
no doubt possess the chemistry to combat a much greater range of pathogens.
Yet these forests are fast disappearing to satiate the West's appetite
for tropical hardwoods. The relentless pressures of the timber industry
will result not only in the decimation of food sources for humans, primates
and other species, but also in the total loss of precious medicinal plants
essential to the well-being of man and apes in tropical regions.
Don Cousins
Don Cousins has had a lifetime interest in the great apes. He has worked in Twycross and Chessington zoos, and in 1957 visited Gabon to look for gorillas. He has researched and published widely on the subject and was a friend and colleague of Dian Fossey.