Temporal Landscape Partitioning among Baboon (Papio cynocephalus) Social Groups

Abstract

Many social animals live in relatively stable groups, and often these groups occupy partially overlapping home ranges. This non-exclusivity raises fundamental questions about how groups temporally partition the landscape, defined as shared yet non-synchronous use of the same resources. The most proffered theoretical explanation is that social dominance hierarchies mediate temporal landscape partitioning by influencing where and when individuals travel within regions of home range overlap. However, few studies to date have assessed how competition between groups affects their spatiotemporal interactions. My main objective was to address this topic by quantifying the factors influencing temporal landscape partitioning among conspecific groups in a well-characterized population of wild baboons (<italic>Papio cynocephalus</italic>). These empirical results were used to develop a theoretical framework against which fitness benefits of social dominance as they relate to spatiotemporal organization can be tested in other species, including non-primates.

Baboons, like many other cercopithecine primates, live in stable multimale-multifemale social groups. I found that annual home ranges of neighboring groups overlapped substantially, yet groups were less often in close spatial proximity of one another than predicted by a biologically informed null model. When direct intergroup conflict occurred, the winning group was predicted by differences in the number of adult males in each group (a demographic component highly correlated with group size) and groups that had used the area surrounding the encounter location more intensively than their opponent over the preceding 9 or 12 months. Spatial consequences of agonistic encounters affected only losing groups; this effect was strongest in the 3 months immediately following the interaction. Despite the competitive advantage of larger groups, I found that intermediate-sized groups had energetically optimal space-use strategies, potentially reflecting relative pressures of intra- and intergroup competition. These space-use patterns are arguably determined both by the distribution of foraging resources and the availability of limited sleeping sites, which anchor daily movement. Groups asynchronously shared sleeping sites (multiple groups rarely occupied the same sleeping site on a given night), resulting in short time intervals (<3 nights) until a subset of preferred sites were reused at the population-level. This near-continuous occupation of preferred sites implies that groups risk predator detection, parasitic infection, and local forage depletion at these sites. The high frequency of their use despite these costs suggests that benefits accrued may offset these risks. Specifically, the physical attributes predicting frequency of site use may minimize the risk of successful predation because preferred sites offer opportunities for escape if a predator attacks. Finally, I examined health consequences of spatiotemporal resource availability, providing a novel description of probable copper deficiency in a wild primate population consistent with copper deficiency as described in humans, ungulates, and laboratory primates. Patterns revealed in these studies on the factors proximately affecting the allocation of resources among social groups provide testable hypotheses for how intergroup resource competition may ultimately affect differences between groups in the average individual fitness of group members.