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Counting Gorillas

  • Sunday, March 1, 1998

A comprehensive census in Uganda's Bwindi Impenetrable Forest National Park has confirmed the existence of nearly 300 mountain gorillas.

The world's total number of mountain gorillas has been estimated for some time at just over 600; the other 300 members of this endangered species live in the Virunga Volcanoes along the adjoining borders of Rwanda, Uganda and the Democratic Republic of Congo (formerly Zaire).

The Bwindi study was conducted last Fall by the Wildlife Conservation Society, the International Gorilla Conservation Program (IGCP, a joint project of AWF, the World Wide Fund for Nature, and Fauna and Flora International), the Institute of Tropical Forest Conservation and the Uganda Wildlife Authority. In addition to counting the mountain gorillas, researchers sought demographic data, such as birth rates, group size and gender and age statistics. They also gathered information on population densities and distribution of other large mammals, on vegetation and on levels of illegal human disturbance within the park.

Six teams of census takers counted 292 individual gorillas living in 28 groups, along with seven lone silverback males. Researchers stress that the total may err on the low side since extra precautions were taken to avoid double-counting. The population, they say, may be as high as 305.

The teams, composed of scientists and national park staff members from Uganda, Rwanda and Congo, followed trails and counted nests, using survey techniques developed in the Virunga mountains. This was not easy, as the Bwindi Impenetrable Forest has come by its name honestly. Steep inclines and dense, thorny brush make it hard for humans to maneuver. Compounding the task was the gorilla habit of building new sleeping nests every night, raising the possibility of double counting.

The teams collected gorilla hairs, which will be DNA-fingerprinted and used to compare the genetic links between the Bwindi and the Virunga gorillas. As a rule, Bwindi's gorillas have shorter hair and slightly longer limbs.

The results of the census were discussed at a Population and Habitat Viability Analysis Workshop held in Uganda in December. Elizabeth Macfie, D.V.M., AWF's program officer for the IGCP in Uganda, told the Wildlife News that the session convened for the first-time park managers, conservation organizations and researchers from the three countries with mountain gorillas to discuss management of the endangered animals.

One workshop effort was the development of a computer model using the census data and other information to help predict future gorilla numbers. The model suggested that if conservation activities continue, the threat to the mountain gorillas can be lessened. But the impact of circumstances beyond the control of park managers, such as civil wars that bring armed soldiers or refugees into gorilla habitat, cannot be predicted.

In other gorilla news, a group of tourists in Bwindi last November became the first humans to witness a gorilla birth in the wild.

The tourists said they came upon the K group with the mother Nyabutomo along with the silverback Kacupira and a juvenile. Nyabutomo, they reported, was lying down, shifting her position as if she were trying to get comfortable. She spread leaves on the ground beneath her. As she grunted, Kacupira offered his arm to support her. She soon delivered what appeared to be a healthy baby.

Unfortunately, the infant did not survive. Park staff reported seeing the mother a month later, but without the infant; the date and cause of death are unknown. Fatalities among the very young in the wild are not unusual, experts say, and seem to be part of the natural scheme of things in the forest.

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