Person:

Wobber, Victoria Elizabeth

Background: Facilities across Africa care for apes orphaned by the trade for "bushmeat." These facilities, called sanctuaries, provide housing for apes such as bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) who have been illegally taken from the wild and sold as pets. Although these circumstances are undoubtedly stressful for the apes, most individuals arrive at the sanctuaries as infants and are subsequently provided with rich physical and social environments that can facilitate the expression of species-typical behaviors. Methods and Findings: We tested whether bonobo and chimpanzee orphans living in sanctuaries show any behavioral, physiological, or cognitive abnormalities relative to other individuals in captivity as a result of the early-life stress they experience. Orphans showed lower levels of aberrant behaviors, similar levels of average cortisol, and highly similar performances on a broad battery of cognitive tests in comparisons with individuals of the same species who were either living at a zoo or were reared by their mothers at the sanctuaries. Conclusion: Taken together, these results support the rehabilitation strategy used by sanctuaries in the Pan-African Sanctuary Alliance (PASA) and suggest that the orphans we examined did not show long-term signs of stress as a result of their capture. Our findings also show that sanctuary apes are as psychologically healthy as apes in other captive settings and thus represent a valuable resource for non-invasive research.

Phenotypic changes between species can occur when evolution shapes development. Here, we tested whether differences in the social behavior and cognition of bonobos and chimpanzees derive from shifts in their ontogeny, looking at behaviors pertaining to feeding competition in particular. We found that as chimpanzees (n = 30) reached adulthood they became increasingly intolerant of sharing food, whereas as adults, bonobos (n = 24) maintained high, juvenile levels of food-related tolerance. We also investigated the ontogeny of inhibition during feeding competition. In two different tests, we found that bonobos (n = 30) exhibited developmental delays relative to chimpanzees (n = 29) in the acquisition of social inhibition, with these differences resulting in less skill among adult bonobos. The results suggest that these social and cognitive differences between two closely related species result from evolutionary changes in brain development.

As many studies of cognition and behavior involve captive animals, assessing any psychological impact of captive conditions is an important goal for comparative researchers. Ferdowsian and colleagues (2011) sought to address whether captive chimpanzees show elevated signs of psychopathology relative to wild apes. They modified a checklist of diagnostic criteria for major depression and posttraumatic stress disorder in humans, and applied these criteria to various captive and wild chimpanzee populations. We argue that measures derived from human diagnostic criteria are not a powerful tool for assessing the psychological health of nonverbal animals. In addition, we highlight certain methodological drawbacks of the specific approach used by Ferdowsian and colleagues (2011). We propose that research should (1) focus on objective behavioral criteria that account for species-typical behaviors and can be reliably identified across populations; (2) account for population differences in rearing history when comparing how current environment impacts psychological health in animals; and (3) focus on how changes in current human practices can improve the well-being of both captive and wild animals.