Mountain gorilla twins are rare — occurring at approximately one percent of births — and raising them is an exceptional physical and social challenge. A nursing gorilla female with a single infant invests an enormous proportion of her daily energy in the infant’s care. With twins, that investment is doubled, and the logistics of carrying, feeding, and protecting two infants simultaneously push the boundaries of what a single female can manage. The documented case of the Bwindi female who raised twins following the death of her group’s silverback is one of the most closely studied examples of exceptional gorilla maternal behaviour in the research literature.
The Birth
The twin birth was detected by the UWA monitoring team during a routine morning check on a habituated group in Rushaga sector. The female — an adult of approximately fourteen years, with one previous surviving infant — had given birth overnight. The monitoring ranger noted immediately that there were two infants rather than one: a male and a female, both alive, both nursing. The Gorilla Doctors team was notified and assessed the twins within twenty-four hours. Both were below the typical birth weight for singleton gorillas, which is expected with twins, but both were nursing and maintaining normal temperature.
The group’s silverback was present at the time of the birth. His death — from a respiratory illness documented by Gorilla Doctors as consistent with a natural pathogen rather than human transmission — occurred when the twins were six weeks old.
What the Silverback’s Death Changed
The silverback’s death produced the social disruption described in the dynamics of silverback loss. Several adult females transferred to other groups. The female with the twins faced the choice of transferring or remaining with the reconstituting group. She remained — researchers believe because the physical burden of moving two six-week-old infants while also seeking to join a new group’s social structure was prohibitive. She became, effectively, a lone female managing two infants with the reduced social support of a transitional group.
The monitoring team and Gorilla Doctors maintained elevated observation frequency throughout the following year. What they documented was a female managing an extraordinary physical workload with apparent competence: carrying both infants simultaneously when moving, alternating nursing between them, and positioning them at night in a way that maintained warmth for both. Other adult females in the reconstituting group occasionally assisted with holding an infant — a behaviour called allomothering — providing the female with brief periods of reduced load.
The Survival Rate
Both twins survived their first year — an outcome that researchers characterise as exceptional given the circumstances. The female twin was lighter at one year than a typical singleton would be at the same age, but both were active, nursing, and developmentally normal in their motor and social behaviour. At eighteen months, the Gorilla Doctors team assessed both as thriving.
The female who raised them is still a member of the reconstituted group. The twins, now juveniles, are identifiable to the guides who accompany trekking groups at Rushaga — the male by a distinctive facial marking, the female by her slightly smaller size relative to her brother. Visitors to the group in 2027 may observe both. The gorilla permit costs $800. What it sometimes gives you is the chance to meet individuals whose survival required something extraordinary from the creatures who raised them.
