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Abstract
Gibbons are small, diurnal, arboreal apes and are most vulnerable to predators at night while they sleep. Previous research has shown that gibbons across a range of species exhibit cryptic pre-sleep behaviors, select sleeping trees with characteristics that may protect them from predators, and exhibit infrequent and irregular reuse of these sites. This study focuses on a group of white-handed gibbons (Hylobates lar) living in a savannah habitat with an intact predator community. I looked at antipredation strategies, intragroup variation in sleeping tree characteristics, and the influence of forest type on sleeping tree selection. As predicted, these gibbons exhibited cryptic pre-sleep behaviors and selected sleeping trees similar to those observed in prior studies. Rates of sleeping tree reuse, however, were unusually high. Since sleeping tree reuse in this study followed a pattern of temporal clustering, higher rates of observed reuse may be influenced by a more continuous sampling of sleeping trees. Additionally, I argue that higher rates of sleeping tree reuse may be attributed to higher levels of predation pressure in combination with a suboptimal forest structure. Differences in sleeping tree canopy preferences between the adult individuals and the subadult were notable and may relate to size differences and therefore distinct predation pressures between age classes. The subadult's preference for denser foliage in sleeping trees could also be driven by a biological need for better sleep quality, as wind has been identified as a key factor affecting sleep among captive gibbons. Though forest type has been shown to exert an influence on habitat use in this same population, observations revealed no significant effects on sleeping tree location in this dataset.