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Category: Data

Description: Sumatran orangutans (Pongo abelii) are a critically endangered primate species that have experienced sharp population declines over the last half-century. Orangutans are largely solitary and arboreal animals in the wild, making well-being and stress research on the more constricted and social captive individuals important. This study sought to evaluate stress and non-stress related behavior in captive orangutans at the San Diego and Saint Louis Zoos. These groups were chosen due to similarities in their group demographics (count, sex, age) and differences in their enclosure environments (one group is housed in a mixed-species enclosure with siamangs). It was hypothesized that the Saint Louis orangutans would show less stress-related behavior, higher frequencies of arboreality, and lower frequencies of interaction and close proximity associations compared to the San Diego orangutans. Forty hours of observational data was conducted including a mixture of in-person (Saint Louis) and webcam (San Diego) instantaneous group scans and continuous focal follows to create a matched sample between the populations. Stress-related behaviors were found to be slightly higher in Saint Louis although both populations displayed remarkably low frequencies of stress-indicative behaviors. Arboreality and social behavior was shown to have higher frequencies among the San Diego orangutans, though using these as clear-cut indicators of stress and non-stress requires further research considerations. Overall, this study found that captive orangutans may not have the same preferences as wild orangutans.