Summary

1. Gelada baboons (Theropithecus gelada) are found mainly on the Amhara highlands in Ethiopia at altitudes ranging between 1500–4500 m. Recently, a new population was found in the Arussi region (Mori & Belay, 1990).

2. The gelada habitat is characterized as wet and cool compared to that of lowland baboons. The higher the altitude, the longer the vegetation is kept green, because of the high rainfall and low temperature.

3. Gelada baboons can achieve higher population densities and biomass compared to other sympatric primates and ungulates; this is made possible by their efficient food processing techniques and anti-predator strategies, including group living and the use of cliffs as refuges.

4. They are highly graminivorous, with grasses forming more than 90 per cent of their diet in most habitats and seasons. However, when the availability and the nutritional content of grasses declines, they shift to eating herbs.

5. At present, we know little about the digestive processes that enable gelada to achieve a high biomass. 6. The time spent feeding is the highest level among herbivorous primates, ranging from 67 per cent in the high Simen to 36 per cent at Bole.

History of field studies on gelada baboons

All of the ecological field data on gelada baboons (Theropithecus gelada Rüppell) were accumulated during a single decade (1964–75). John H. Crook carried out his pioneer study on this species in Ethiopia in 1964–5. He was able to provide a basic description of the species' social system as well as the species' unusual ecology (Crook, 1966; Crook & Aldrich-Blake, 1968).