Covering Behavior Using Flexible Materials in a Captive Bornean Orangutan (Pongo pygmaeus)

Environmental enrichment provides captive orangutans with opportunities to express species-typical behaviors. One behavior seen in captive orangutans is covering with flexible materials, but its function is not well understood. This study provides a quantitative description of covering behavior in a captive Bornean orangutan (Pongo pygmaeus). Behavioral observations were used 5-min scan sampling with continuous recording of material-related bouts across eight sessions. Covering behavior was observed using cloth and natural vegetation, indicating flexibility in use. Covering behavior was not significantly associated with sun exposure, suggesting that it is not solely response to solar conditions. However, covering behavior occurred more frequently during inactive states and was characterized by significantly longer bout durations than non-covering material interactions. These findings indicate that covering represents a distinct and sustained behavioral category rather than transient object manipulation. The use of different materials and the prolonged nature of covering bouts suggest that this behavior may serve multiple functions, including comfort, environmental regulation, and interaction with enrichment. This study provides evidence for a rarely described behavior in captive orangutans and highlights the importance of providing manipulable materials and environmental choice to support behavioral flexibility and welfare.