Ecological and social determinants of spacing behaviour in desert baboon groups

This paper investigates the determinants of individual spacing behaviour in a desert baboon population (Papio cynocephalus ursinus). Patterns of neigh bour proximity and neighbour density were examined among adults in four gro ups under different ecological and social conditions (through instantaneous sampling during focal follows). Initial analysis of these data shows that (1) the use of vertical substrates (refuges such as tall trees and cliff fa ces) can confound patterns of spacing, and (2) individual differences in sp acing can depend on the spatial scale over which it is measured. To minimis e these substrate and scale effects, this analysis focuses on animals which are off refuges and examines spacing behaviour through its underlying stat istical 'dimensions' (identified through factor analysis). Analysis of thes e dimensions indicates that sex, group size, activity-habitat and female re productive state can all have independent effects on spacing: (1) males are more dispersed than females in smaller groups, (2) male and female dispers ion increases with time spent in foraging habitats, and (3) female dispersi on is reduced during lactation. According to the hypotheses tested, these r esults indicate that feeding competition only affects spacing behaviour dur ing foraging while predation risk plays little or no role in spacing. Most aspects of spacing behaviour are best explained by male reproductive strate gies and their social repercussions.