Bamboo shoots were the gorilla’s most concentrated form of protein. They provided abundant liquid too and made up more than 14 percent of group 5s annual diet. Schaller had also noted the importance of bamboo. Yet between his study area on Mt.Mikeno in Congo and group 5 s ranges on the boarder of Rwanda’s Parc des Volcans, there were gorilla families that almost never ate bamboo. One of those was group 4 the ill-fated clan of Uncle Bert and Digit, the long term study group of Dian and now David occupying the higher elevations in the Visoke saddle, group 4 rarely descended low enough on either side to find bamboo stands. Perhaps it was a cultural matter and they really didn’t like bamboo, or perhaps they preferred their concentrated stands of nettles. May be they didn’t like the competition from other gorillas. Left forever un known is the question of whether or not group 4 might have had easier access to bamboo if extensive lower elevation stands had not been converted to farm fields.
One unexpected discovery was the gorilla’s interest in ants. Amy has already seen that the gorillas would actually fight over Vernonia galls infested with insect larvae. Claims of vegetarian purity were dealt another blow as she collected evidence of their predilection for ants. At first she saw gorillas popping driver ants into their months as they groomed themselves. But Amy thought this might just be the easiest way to kill and rid their fur of a hard biting pest that had somehow made its way onto their bodies. Then she discovered whole driver ant bivouac ripped apart by the gorillas, after which prodigious amounts of undigested ant body parts could be found in their dung. This was far from the carnivorous and even cannibalistic tendencies discovered in chimps, but it indicated a more complex diet than had generally been presumed.
The gorillas were certainly selective in their food choices. Bamboo shoots and galls were sources of competition, bruised feelings and occasional physical violence. So, too were black raspberries and stalks of juicy celery during the dry season. Shelf fungus offered a rare treat whose taste and high protein content were apparently worth fighting for. If young gorillas discovered the fungus, they would usually nibble on it until displaced by an elder. Older gorillas would simply break off a large chunk and then try to slip discreetly away from the rest of the family. Gorillas rarely carried food of any kind, but shelf fungus and bamboo shoots were notable exceptions.
Some other resources were equally rare, but shared in a much more communal fashion. Every couple months, Beethoven led his band to a particular site on the flank of Bonde ya kurudi, or return ravine. There they would sit like patients outside a doctor’s office adults sitting, youngsters playing –waiting their turns as one gorilla at a time entered a small cave like opening.
Once finished, that gorilla would exist with rouged lips and a belly covered with reddish clay. Later analysis’s confirmed the clay to be high in iron, as Amy suspected, but it remained unclear why the gorillas needed this mitral supplement. Nor has this habit been noted in any other Virunga gorilla group. Another group 5 favorite was the root of the giant Lobelia plant. Here too a purposeful expedition was required to reach one of the several subalpine locales where the plant thrived on exposed high mountains slopes. At the site, the adult gorillas would spread out to find choice plants, while the youngsters waited nearby for access to the products of their digging. Once the roots were exposed, the gorillas selected strands that they pulled between their teeth, efficiency tripping and eating the prized epidemics. This paper like root bark was the one food source that Amy did not collect. In addition to funding no substitute technique for removing the b ark, she didn’t want to add any burdens to the already stressful, high elevation existence of the Lobelia.
It’s important to the gorillas thus remains a mystery. What is certain is that gorillas exert considerable physical and cooperative effort to obtain this rare resource.
Once indelicate feeding habit of mountain gorillas seemed to hold particular appeal for a single group 5 lineage .Effie and her off spring, puck and Tuck, were all partial to eating the dung of other gorillas. It was an irregular habit, most common on rainy days, lading one former researcher to equip that it was” a hot meal on a cold day”. In more prosaic terms, the behavior likely signaled a dietary deficiency, or a need to replace depleted intestinal fauna, that was met by obtaining the desired supplement direct from another gorilla source. Whatever the rational explanation might be, it was not attractive to watch four year old Tuck munching on a steaming lobe of Beethoven’s dung. But the gorillas are not here to meet our expectations.
AMY SPENT MORE THAN two thousand hours observing group 5 to complete her feeding ecology study. Five-hour focal formed the heart of her work, augmented by a single twelve hour, dawn to dusk focal on one individual in each of the six age and sex classes. The mentally and physically demanding work required an extremely high level of concentration and attention. While the demands of recording the details of gorilla feeding for hours at a time numbed the body. Rain gear could keep most of the body dry, but Amy’s feet were lost cause. Rubber boots kept the water out only to replace it with sweat from the inside. And no leather body in those days could earn the Virunga “water proof” label. Cold was even worse than wet, and the combination of the two could easily cause hypothermia if one didn’t stay active. Moving around wasn’t an option, however during extended focal. Amy learned to read the feel of the air low clouds were ever present and not too helpful to predict the arrival of rain and quickly throw on a thick oiled wool sweater under her rain jacket. The broad leaves of certain plants, when available provided welcome over for her boots. But nothing could protect her hands if the gorillas continued feeding in the rain, Amy would write inside a plastic bag. This kept her paper dry, but rubbing against the condensation of the bags interior produced chronic deep cracks in her fingers, which didn’t heal for weeks at a time during the long rainy season. Worse, the exposure and tight writing style required by small note books caused constant cramps. Sometimes her fingers just stopped working. Cape buffalo encounters offered a great way to restart the blood flow Amy’s schedule of alternating dawn departures and dusk returns assured daily exposure to peak buffalo activity periods. Moving quickly through the thick Virunga understory, one easily misses the creature’s bulky black form in dim crepuscular light. Suddenly a six foot tall, half ton frame looms in the path only twenty feet way. Three foot horns curl out from a massive base on the head to form dagger-sharp tips. Dark liquid eyes reveal no apparent thought process inside. The combination of lethal force, limited analytical powers and a nasty temper make the cape buffalo the most deadly of Africa’s vast array of dangerous species. This was no reassuring when Amy was armed with only a walking stick or machete and good climbing trees were rare. Fortunately despite a score of close encounters with buffalo, she dove into nearby bushes and held her breath as the buffalo rumbled past.