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.

Recent research suggests that some human-like social skills evolved in dogs (Canis familiaris) during domestication as an incidental by-product of selection for “tame” forms of behavior. It is still possible, however, that the social skills of certain dog breeds came under direct selection that led to further increases in social problem solving ability. To test this hypothesis, different breeds of domestic dogs were compared for their ability to use various human communicative behaviors to find hidden food. We found that even primitive breeds with little human contact were able to use communicative cues. Further, “working” dogs (shepherds and huskies: thought to be bred intentionally to respond to human cooperative communicative signals) were more skilled at using gestural cues than were non-working breeds (basenji and toy poodles: not thought to have been bred for their cooperative-communicative ability). This difference in performance existed regardless of whether the working breeds were more or less genetically wolf-like. These results suggest that subsequent to initial domesticating selection giving rise to cue-following skills, additional selection on communicative abilities in certain breeds has produced substantive differences in those breeds’ abilities to follow cues.

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.

The cooking hypothesis proposes that a diet of cooked food was responsible for diverse morphological and behavioral changes in human evolution. However, it does not predict whether a preference for cooked food evolved before or after the control of fire. This question is important because the greater the preference shown by a raw-food-eating hominid for the properties present in cooked food, the more easily cooking should have been adopted following the control of fire. Here we use great apes to model food preferences by Paleolithic hominids. We conducted preference tests with various plant and animal foods to determine whether great apes prefer food items raw or cooked. We found that several populations of captive apes tended to prefer their food cooked, though with important exceptions. These results suggest that Paleolithic hominids would likewise have spontaneously preferred cooked food to raw, exapting a pre-existing preference for high-quality, easily chewed foods onto these cooked items. The results, therefore, challenge the hypothesis that the control of fire preceded cooking by a significant period.