The relationship between altitude and group size in mountain baboons (Papio cynocephalus ursinus)

Abstract

Twenty-seven troops were counted during a 1989 census of the mountain baboon population at Giants Castle Game Reserve. In contrast to earlier findings, and despite a similar population structure, we found no relationship between group size and altitude. We argue that this is a consequence of long-term population processes whereby groups split as they grow larger and, in some cases, as their home ranges expand upward. At these high altitudes, smaller groups are eventually subjected to environmental conditions that destroy them. We propose that the high-altitude slopes act as a demographic sink.