Mushamuka's Story: The Largest Group and the Longest Tenure

When his appearance was first recorded in 1971, Mushamuka was already fully matured. Adrien Deschryver, the first warden of the Kahuzi-Biega National Park, tried to habituate two groups of gorillas in the late 1960s and began taking visitors to these groups in the early 1970s. Mushamuka was the leader male in one of these two groups. Mushamuka means old and wise man in the Mashi language. Alan Goodall, who studied the Mushamuka group in 1972, called him Kelele (noise in Swahili) in his book entitled The Wandering Gorillas. The group had 20 gorillas with 2 silverback males, 1 silverback/blackback male, 3 blackback males and 4 females at that time.A big change came in 1975. The leader male of a neighboring group, the other habituated group, was wounded in several fights with a lone silverback and died. Several females were lured away from this group, moved with the lone silverback, and finally transferred into the Mushamuka group. The size of Mushamuka's group rose to 31 with 12 females in 1976 and to 42 with 17 females in 1978, which is the largest group size of wild gorillas in their natural habitats.
From 1979 to 1983, several maturing silverback or blackback males left the group. They took females and immatures to form new groups. Some females transferred into neighbouring groups. These movements resulted in reduction of group size by half until 1983. Another four maturing silverbacks left the group in 1984 and 1985.
Mushamuka was tolerant toward these males, who occasionally mated with females. Nevertheless, these males emigrated from the group before maturity. Mubalala, a son of Mushamuka, also left the group at 13 years old in 1986 and took five females from the group. He stayed in the peripheral part of Mushamuka's range and encountered with other groups frequently. He acquired several females during these encounters and the group size rapidly increased.
Nindja, another son of Mushamuka, gradually left the group. In 1987 he became a silverback at 12 years old and started to copulate with females. Mushamuka was very tolerant toward him, and several females were always around him. The group frequently splitted into two subgroups, one of which included Nindja and females. When he left the group in 1989, five females (1 adult, 2 young, 1 juvenile and 1 infant) followed him and they formed a new group. Nindja encountered with the other habituated group at the end of 1989 and fought with its leader male called Maheshe. After several fierce fights, Maheshe was seriously wounded, and Nindja acquired another females with immatures from the Maheshe group.
Another maturing son (Bwana) of Mushamuka also left the group with a few females in 1992. Maheshe disappeared in November 1993 for unknown reason (later it was proved that he had been killed by poachers), and the Maheshe group travelled without any silverback male. Lambchop and Mintsauce, maturing silverback males of the Mushamuka group, occasionally visited the Maheshe group. Lambchop finally associated with Maheshe's females since March 1995, and Mintsauce started to travel alone at the same period. The number of females decreased in the Mushamuka group probably because of Mushamuka's reproductive inability. Two infants were born in 1993. One infant was born in 1994 but died at 1.5 month old. Since then, no birth was recorded in the Mushamuka group.
Mushamuka disappeared in April 1997 and was estimated to die of old age. His appearance was very old with lean face, wrinkled neck and lost teeth. His estimated age was 43-46 years at this time. He has been known as a leader male since 1971. It means that he led the group for at least 26 years, which is the longest tenure of male gorillas known in the world. After he was lost, 2 young males at 8-9 years old, 3 females and 3 independent immatures moved by themselves without any adult male. Mushamuka's story was reconstructed by the data collected by John Kahekwa, Serundori Eloi, Mankoto ma Oyisenzoo and myself. Serundori was one of the guides who habituated Mushamuka in the early 1970s, and John initiated the recording of demography of all habituated groups in the early 1980s. Mankoto has been working as Park Warden since 1987 and established the monitoring system for each habituated group.
The demographic changes recorded in the Mushamuka group during 26 years were similar to those of mountain gorillas in the Virunga Volcanoes. They form uni-male cohesive groups. Both males and females tend to emigrate from their natal groups before maturity and only males spend a solitary life before establishing new groups. However, some aspects of individual movements are different from the Virunga gorillas.
Firstly, when leaving their natal groups, some maturing silverback males took females away from the group and formed new groups without experiencing solitary life. Such cases have rarely been recorded in the Virunga Volcanoes, and most males tend to travel alone for several years before acquiring female partners there. Secondly, when females transferred into other groups, they were often accompanied by immatures. Some females were even accompanied by newborn babies, and they were accepted by the new silverback males who were not biological fathers of these babies. In the Virungas, immatures rarely transferred into other units with their mothers or by themselves possibly because of frequent infanticide by the new males. All the infants transferred with their mothers were killed by the leader males of the new groups. By contrast, no infanticide has been recorded in the Kahuzi region.The lack of infanticide may be responsible for relatively free movements of immature gorillas in the Kahuzi region. It may also influence male dispersal after maturity and females' choice to transfer. Most sons of Mushamuka tended to stay in the peripheral part of Mushamuka's range after emigration and form their own groups with familiar females instead of traveling alone. Mubalala, Nindja, Lambchop and Bwana are sons of Mushamuka. All of them have established their range around their father's range to form a patrilineal community. We are now analyzing the demographic data on the habituated groups of gorillas in the Kahuzi-Biega National Park. Although the data were still insufficient to realize the life history of such long living animals, this analysis will hopefully find some unique features of their social life which seems to be different from that of mountain gorillas.

Juichi Yamagiwa

Prof. Dr. Juichi Yamagiwa has been involved in field work of eastern gorillas since 1978, mainly at Kahuzi-Biega. He studied gorillas at Karisoke in 1981 and 1982 and conducted extensive surveys at Masisi and Itebero from 1987 to 1991. He promoted a cooperative research project on gorillas and chimpanzees at the Tshibati area of Kahuzi-Biega with CRSN and IZCN/ICCN.

Change in Age-sex Composition of the Mushamuka Group

Age classes: Silverback: male over 13 years old; Blackback: male 8-12 years old; Adult female: over 8 years old; Independent immature: 4-7 years old; Dependent immature: 0-3 years old

Kahuzi-Biega overview

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