East Africa’s Prized Silverbacks
Uganda and Rwanda are the only countries in East Africa where mountain gorillas can be trekked. Mountain gorillas are globally recognised as an endangered species. In the whole world, there are only about 1000 individual mountain gorillas, and over 400 of these are found in Uganda’s Bwindi Impenetrable National Park. A population of over 240 individuals can be encountered in Rwanda’s celebrated Volcanoes National Park.
Who is a silverback?
Silverbacks are adult male gorillas. They standout at an average weight of 195kg and a height of 168cm, usually weighing twice as much as the females. The tallest silverback that has been recorded was 1.95m, with an arm span of 2.7m, a chest of 1.98m, and a weight of 219kg. The heaviest silverback recorded weighed 267kg and measured up to 1.83m in height. Adult males are called silverbacks because they normally have a saddle of grey or silver-coloured hair which develops on their backs with age. The hair on their backs is much shorter than that on most of the other body parts. The other outstanding feature that distinguishes the adult males is their pronounced bony crests on the very top and back of their skulls, which gives their heads a more conical shape. Like other gorillas, the silverbacks feature dark brown eyes framed by a black ring around the iris.
Silverbacks are usually dominant heads of their groups. Mountain gorillas are highly social, they live in relatively stable groups bound together by long-term bonds between adult males and females. The dominant silverback will defend his group rather than his territory. The average length of tenure for the ruling silverback is usually between 4 – 5 years. Most mountain gorilla groups in East Africa are comprised of one adult male and a number of females. A few groups have more than one adult male and others are all-male, usually comprised of one mature male and a few younger ones. Group sizes vary from 5 – 30 individuals, with an average of ten members per group. A typical mountain gorilla group has; one dominant silverback who stands out as a the group’s undisputed leader, a subordinate silverback who is usually a younger brother or half-brother or an adult son of the reigning silverback. The other members in the group can include; one or two black-backs who act as sentries, 3 – 4 sexually mature females who are uniquely bonded to the dominant silverback for life, and 3 – 6 juveniles and infants.
Like any other mountain gorillas, the silverbacks are terrestrial and quadrupedal. They can however climb into fruiting trees whenever the branches can bear their weight. They are diurnal; most active during the day. Silverbacks spend most of their hours eating, since they need large quantities of food to sustain their massive bulk. They construct new nests every evening from the surrounding vegetation to sleep in. The size of home or area occupied by a silverback and his group varies and is influenced by the availability of food sources. The home range usually includes several vegetation zones to give the family a variety to feed from.
The heroic role of the silverback
The ruling silverback plays a great role in determining the movement of the group and its feeding sites all through the year. When it comes to conflicts and disputes within his group, he acts as a mediator to restore peace between the conflicting parties. The silverback also protects the group from external threats. Even at the cost of his own life, the silverback will protect his group from human, wild animal and other gorilla group attacks. The dominant silverback is a heroic figure, the centre of attention during rest sessions as the young gorillas usually stay close to him and make him a part of their games. Within the group, if a mother dies or abandons the family, it is the silverback who takes over the care of the abandoned little ones, to the point of allowing them to nestle in his nest. A silverback is usually experienced and capable of removing poachers’ snares from the body parts of his trapped group members.
The absence of the silverback is not without consequence, should he die or be killed by accident, disease or poachers, the group is most likely to be disrupted. With the death of the dominant silverback the group splits unless there is an accepted male relative capable of taking over his position. Though rarely done, the group can adopt an unrelated male. In such a case, this newly chosen silverback can decide to kill all the infants of the dead silverback.
Conflict and war
Although dominant and strong, the silverbacks have been surprisingly noted to be shy and gentle. Outbreaks of conflict and war are rarely heard of in stable groups because the silverbacks are known to be good at their mediatorial role. Conflicts are usually external. When two mountain gorilla groups meet, their ruling silverbacks usually engage in a fight to the death. They attack with their canines, causing deep, gaping injuries on each other’s bodies. To counteract deaths however, conflicts are most often resolved through dramatic displays and threat behaviour aimed at intimidating the opposing party without becoming physical. The ritualized charge display includes; the silverbacks progressively quickening their hooting, engaging in symbolic feeding, rising bipedally, aggressively pulling at and throwing around vegetation, chest beating with cupped hands, one-leg kicking, running sideways and thumping the ground with their palms.
Silverbacks in Uganda
Throughout the year, tourists flock Uganda and Rwanda to encounter the countries’ habituated mountain gorilla families. Each of the habituated gorilla group has one or more silverbacks who are recognised as the family heads. In Uganda’s Bwindi Impenetrable National Park, several groups can be encountered; Mubare, a family of 11 members led by a silverback called Kanyonyi. He replaced silverback Ruhondeza who tragically died in 2012. Found in Buhoma region is Habinyanja, a family of 17 members led by silverback Makara. Also found in Buhoma is Rushegura, a family of 16 members led by silverback Kabukojo. Found in Ruhija is Oruzogo, a group of 17 members led by silverback Bakwate. Also found in Ruhija is Bitukura, a family of 13 members led by silverback Ndahura. The family has 4 other silverbacks, 4 adult females, 4 juveniles and 3 infants. Kyaguliro is the other group found in Ruhija, it consists of 20 members who live in 2 subgroups, with each group having 10 members; group A is led by silverback Rukara and group B is led silverback Mukiza. Found in Rushaga region is Nshongi group, a family of 7 members headed by silverback Bweza. The family has only 1 silverback, 3 adult females, a sub-adult, a juvenile and an infant. Mishaya is the other group found in Rushaga, it is comprised of 12 members and is headed by silverback Mishaya. Kahungye is also found in Rushaga. The group is comprised of 17 members and is led by silverback Rumanzi. The other members include; 3 silverbacks, 3 blackbacks, 3 adult females, 3 sub-adults, 3 juveniles and 2 infants. Also found in Rushaga is Busingye, a group of 9 members created as a result of a breakaway from Kahungye group. Also created as a result of a breakaway is Bweza, a group of 12 members headed by silverback Kakono. Found in Nkuringi region is Nkuringo, a group of 12 individuals headed by silverback Rafiki. The other group members include; 2 silverbacks, 1 blackback, 2 adult females, 2 sub-adults, 3 juveniles and 2 infants.
Found in Uganda’s Mgahinga Gorilla National Park is Nyakagezi gorilla group, a family of 10 individuals headed by silverback Mark. The other group members include; 5 silverbacks, 2 adult females, 2 juveniles and 1 infant.
Silverbacks in Rwanda
Rwanda’s habituated gorilla families include; Susa, a group of 29 members including 3 silverbacks. The group was named after Susa river and was the largest mountain gorilla family before it split. The group rose to its peak of fame when one of its females bore a set of twins; Impano and Byishimo. Karisimbi is another group, it is a family of 15 members including 3 silverbacks and it is also referred to as ‘Susa B’ because it is the group that split from the original Susa family. Also found in Rwanda is Sabinyo, a family of 12 members including 2 silverbacks. Amaharo group is a family of 17 members including 1 silverback. ‘Amahoro’ means peace in the Kinyarwanda dialect. The group got its name because of the peaceful and gentle nature of its members. The other groups include; Umubano, a group of 11 members including 1 silverback, Kwitonda, a group of 18 members including 2 silverbacks, Hirwa, a group of 12 members including 1 silverback. Agasha, a group of 25 members including 2 silverbacks. Bwenge, a group of 10 members including 1 silverback, and Ugyenda, a group of 11 members including 1 silverback.