Ecology of the Gorilla
Gorillas are vegetarians. In the Virungas, they eat at least 58 different food plants mostly leaves, stems and the bark. Compared to Virunga, Bwindi has many more plant species.
The gorillas eat 60 different plants and fruits.
On rare occasions, they eat insects, nails, soils and dead plants.
Many gorilla foods are concentrated in the bush, secondary growth of forest clearings and disturbed sites. The presence of these areas may affect the abundance of gorillas in some habitats. The high-altitude forests of the Virunga volcanoes have a more open canopy, with bush undergrowth spreading evenly throughout the forest. Gorillas depend on disturbed sites and tend to have smaller home ranges than those in Bwindi and other dense forests.
The plants that gorillas eat include; bamboo shoots, giant thistles and lobelias.
Crunchy wild celery contain a lot of water which explains why gorillas can go for much of the year without drinking water. They sometimes drink from streams during the dry season, and lick water from heavy rainstorms.
Just like humans, gorillas have a single stomach and rather long intestines, which is less efficient for digesting vegetation than the multi-chambered stomach of Colobus monkeys and the hoofed ruminants. This explains why they must eat large of vegetation daily (over 20Kgs for an adult male), and always look bloated.
Social Organization of Gorillas
Gorillas mostly live in family groups. An average group contains 12 animals, with one or two older silver back males, younger black males, several females and their offspring, although they have no set pattern for group composition or size. Groups of thirty animals (with five silver backs), have been recorded, and smaller family groups, composed entirely of males. In Virunga, up to 40% of the groups are multi-male.
Because of strong bonds between individuals, gorillas tend to stay together. The strongest of these bonds are between the females and the silver back male. He is a fully adult male whose hair is grey, a clear sign of his age, which of course indicates; his many years of survival, experience and health. Secondary silver back males, who in most cases happen to be related to the leader, possibly being son or half brother, are a common phenomenon. Though rare, a young silver back not contented with a subordinate position in the group, will usurp the position of his elder. It is important to note that the head silver back is the group’s primary defender, and invariably father of most infants born in the group.
Males in multi-male groups have weak relationships, which they maintain by a voiding conflict. Although they may co-exist in groups for years, they will leave if they fond an opportunity to reside with females elsewhere.
Among females, social relations are largely determined by kinship, with bonds between particular groups sometimes being very strong.
A female’s status is a combination of many factors or absence of young, and her relationship to the dominant male. Although black males come next to the hierarchy, they sometimes out rank particular adult females. Nearly all females and most black back males leave the group of their birth shortly after reaching maturity. This helps to prevent inbreeding in this tiny population, although mating between closely related adults has been seen.
Compared with other primates, gorilla social behaviour is calm and conflicts within gorilla groups are few and far between. The most common conflicts within a gorilla group are minor confrontations over feeding areas or right of way.
A dominant silver back may fight with subordinate males of challenged, but usually keeps control through vocalisation and displays, rather than violence. Transfer of power in a gorilla group can be violent when younger males or intruding silver backs drive out the leader.
However, an incredible serenity usually prevails as a dominant male grows and even dies of natural causes while still leading his group.
Daily habits of Uganda Mountain Gorillas
Gorillas spend about 30% of their time feeding, 30% of their time moving and foraging, and the remaining 40% of the day at rest. They are the most terrestrial of the great apes, spending over 90% of their time on the ground. They move about on all fours, but can stand upright for short periods, particularly to reach food plants or as part of chest-beating display.
They rise at daybreak to travel and fed in the morning, before settling down for a long rest at midday. When foraging, the gorillas may feed as they move, but usually they find an open area where they can spread out and concentrate on having their fill. It is the dominant silverback who invariably determines where they go and where they feed.
During the afternoon, the group typically moves a gain before finding a place to spend the night. Each gorilla makes its own nest every night save for the infants, who sleep with their mothers until weaned at the age of 3-4 years. Nests are usually grouped around the dominant male. However, nests may be spread over 100m or more, particularly in groups where several silverbacks are present. Night nests are usually used once and jettisoned. Typically, gorillas defecate in their nests, and the freshness of the dung is a clue to the age of the nest.
Sometimes, gorillas may sleep late on rainy days, or on mornings after a long trek.
Gorilla groups usually move less than 1 Km on average per day, and rarely more than two. Longer movements typically follow an aggressive interaction or other events that have stressed the group. When travelling, brace yourself for a holy day’s hike if you don’t find feeding sites or you find diarrhetic dung, which is a sign of stressed animals.
Gorilla tracking in Uganda
Mountain gorillas are a preserve of Bwindi and Mgahinga. They are truly special animals, rare, gentle like us yet, yet different. Tracking gorillas is an experience of a life time – It leads you into a strange land to meet one of the world’s most endangered species, in their own denizens. This is an experience, which is humbling as it is thrilling.
Gorilla tracking is an exciting but an energy sapping experience. The guide leads you through the gorilla’s world, explaining aspects of their ecology and unique behaviour, along the way.
In this section, we provide much needed facts about gorillas, relevant both to Mgahinga and Bwindi. In the fore-mentioned parks, specific groups of gorillas have become acclimatized to seeing people. The composition of any group changes as individuals born, die, or transfer, so your guide will be able to give you up-to-date details.
Groups are invariably named after the area in which they range. Therefore, your guide will tell you which group you will visit.
Packing for a Gorilla tours
What to bring for a gorilla tour
§ Wear shoes with good traction, suitable for steep muddy slopes.
§ Gorilla tracking can be a long and grueling walk, so track yourself.
§ Good manners, for gorilla watchers.
§ Carry rain gear, sunscreen and a hat, as the weather is fickle.
§ Carry water and food.
§ Keep your voice down or quiet, you will see and hear more if you do.
§ If approached by a gorilla, back away slowly to keep 5m separation.
§ Don’t point or walk your arms- This can be seen as a threat. Move slowly.
§ Carry binoculars, because you will see much more!. You can hire them at the park office if you don’t have them.
§ Departure is invariably at 8:30am. If you are late, you lose your place because there are always many people in line for stand-by places.
§ When taking photos, you should remember flash is not allowed. Use a fast film (400-800ASA); over expose if possible.
Gorilla Trekking Rules
Rules and Regulations for trekking mountain gorillas in Uganda
§ Don’t drop litter in the park.
§ Keep distance of minimum 5 metres or 15 feet from the gorillas.
§ No eating or drinking near the gorillas.
§ Flash photography is not permitted.
§ In case of an emergency toilet, dig a hole of 30cm and fill it up after use.
§ You ought to stay as a tight group when near the gorillas.
§ No smoking near the gorillas.
§ If you must sneeze or cough, cover your face and turn away from the gorillas.
§ Do not touch the gorillas.
§ Your group must be no more than 6 people and all at least 15 years old.
§ If you have a cold or an infectious disease, do not visit the gorillas.
§ Do not look at the gorillas directly into the eyes.
§ After or before the visit, keep your voices down until 200 metres away from the gorillas.