Orangutan use of vertical space in an innovative habitat

This study measured use of vertical space in an innovative habitat for three adolescent orangutans (Pongo pygmaeus). The indoor habitat was innovative in two main ways: a flooded floor and retractable skylights. It included four large molded trees and interwoven vines throughout 1,620 m³ of space. The exhibit was divided into four vertical levels: skylights, upper canopy, lower canopy, and flooded floor. Five trained observers made instantaneous scans of the exhibit every 5 minutes, in 1-hour blocks of time over a 10-month period, logging 180 hours of observations. One location (of 55) and one behavior (of 53) were noted at each interval. Behaviors were collapsed to form five categories: solitary inactivity, solitary activity, social inactivity, social activity, and eating/drinking. Results showed the orangutans favored the upper canopy, which contained many tree limbs for sitting and reclining. The orangutans next favored the lower canopy and the skylights, especially those skylights that were out of public view. The habitat's flooded floor was avoided (they used it just 1% of the time), as planned by the exhibit designers who intended to showcase these arboreal primates in trees, not on the ground. When compared with wild orangutans, we considered few of their behaviors to be atypical: foraging/eating plastic (vines) and stereo-typed behaviors. Overall, the unique design of the habitat provided opportunities for a range of species-typical behaviors, varying by vertical level, demonstrating the importance of providing sufficient vertical space for orangutans. Zoo Biol 19:239-251, 2000.