STRUCTURE OF GELADA BABOON REPRODUCTIVE UNITS I. STABILITY OF SOCIAL RELATIONSHIPS

(With 2 Figures) (Acc. i6-X-1978) Gelada baboons (Theropithecus gelada) live in one-male reproductive units that contain, on average, one breeding male and 3-5 females and their of fspring (DUNBAR & DUNBAR, I975). These units are known to be constant in composition over periods of at least 6-9 months. Analysis of the structure of social relationships among the members of the unit show that almost all social interactions by adults are with individuals in their own units. However, relatively little is known of the nature of these relationships or of their stability over time. In this paper, data are first presented to show that the structure of social relationships among the adult and subadult members of the unit are stable over time despite the occurrence of events that are likely to disrupt such relationships. Four specific events of this kind will be considered here, namely births, deaths, oestrus and adult male replacement following the take-over of a unit. Second, it will be shown that unit structure remains stable over periods of at least 6-9 months. In addition, data for two units will be presented that suggest that the structure of social relations is consistent over periods of several years. Finally, social relationships among females will be analysed to show that this stability is probably due to a strong tendency for females to interact preferentially with their female kin.