Haven for the night: sleeping site selection in a wild primate

Many animals seek refuge when they sleep, often employing different sleeping sites in successive time periods. Switching from one sleeping site to another might reduce predation or parasite exposure or increase proximity to food resources that are temporally and spatially heterogenous. However, achieving these effects will depend on the synchronous and nonsynchronous use of the same sleeping sites by conspecifics. We assessed the use of multiple sleeping sites by 5 wild baboon (Papio cynocephalus) social groups to evaluate how sites were exploited at both the population and group level. Of 126 woodland sleeping sites used by the study population over ~900 nights of observation, 10 sites were used more than 100 times; these preferred sites accounted for ~60% of all known sleeping sites. On average, individual groups left sleeping sites after 1–2 nights of continuous use, and the same group did not reuse a site for an average of 45 nights. However, at the population level, preferred sites were reused on average every 4 nights. This near-continuous occupation suggests that groups competed for access to preferred sites, perhaps because preferred sites represented better protection from predators, lower parasite prevalence, or had better foraging opportunities nearby. The number of trees in a sleeping site and the time since a site was last used were significant factors distinguishing sites used on a given night by the most dominant versus most subordinate social group. These findings highlight the importance of evaluating resource use at multiple levels of social organization.