Abstract: Sleeping behavior is a necessary life-sustaining activity for non-human primates , but is especially important in the life history of these animals because they spend approximately half of their lifetime sleeping. After a retrospective literature overview, we found that security(imposed by predation pressure), comfort and sanitation are the main factors affecting the selection and utilization of sleeping site by non2human primates. Non-human primates generally display three different choices of sleep site selection, which include arboreal, ground and nesting. By way of conclusion we discuss the differences between species and related environmental effects. The present paper also provides several promising directions for further research.

Key words: Non-human primates; Sleeping site; Selection; Usage