Patterns of movement by baboons in the Drakensberg mountains: Primary responses to the environment

Abstract

The movement patterns of two chacma baboon troops in the Drakensberg mountains of South Africa were studied over an 18-month period. One of these troops (HIGH) lived on the escarpment slopes (1920–2980 m), while the other (LOW) lived primarily in the montane belt (1560–2000 m). In this paper we analyze the effects of environmental variables on day journeys and home range use. We found the troops to be similar in the temporal patterning of their daily movement, in the resistance of travel speed to variations in local climatic conditions, and in their response to the nutritional bottleneck at the end of the austral winter. While both troops traveled farther as food became scarcer, HIGH troop undertook longer day journeys than LOW troop. This was probably due to the interactive effects of absolutely lower food availability and lower ambient temperatures. HIGH troop traveled farther when food was scarcer and when minimum temperatures were higher. Neither variable accounted for variance in the day journeys of LOW troop. Both troops used some areas of their home ranges preferentially. For LOW troop this preference followed the spatial distribution of food. While the same was generally true for HIGH troop, its home range use was complicated by the adverse temperatures of winter and spring. It abandoned the higher, more productive part of its range once temperatures became severe, returning only after minimum ground temperatures had risen above 0°C. These usage patterns differ from those described for eastern African baboon populations and reflect both the severity and sesonality of climate and the poor quality and extreme dispersion of food that characterize these southern mountains.