How orangutans choose where to sleep : comparison of nest-site variables

Primates spend a significant proportion of their lives at sleeping sites, and the selection of a secure and stable nest tree can be crucial for the individual’s survival and fitness. This study examined nesting site preferences of Bornean Orangutans Pongo pygmaeus wurmbii (Tiedemann) in a degraded peat-swamp forest in the Sabangau catchment, Central Kalimantan, Indonesia. Orangutan nests were identified during transect walks. Orangutans most frequently nested in trees in the families Anacardiaceae and Elaeocarpaceae. Orangutans preferentially chose trees with stilt roots or buttresses. We suggest that orangutan nest site selection is driven by comfort and stability rather than predator avoidance. The findings underline the importance of conserving habitat not only for food species, but also for nest-site species.