Leakey Foundation Final Report Social, ecological and reproductive stress in wild female Assamese macaques Julia Ostner, Courant Research Center Evolution of Social Behavior, University of Göttingen; Germany, jostner@gwdg.de
Summary Physiological stress may - if chronic - become detrimental to an individual’s fitness partly due to the immunosuppressive and dysregulatory effects of GC. Although a large body of research on stress exists, there remain large gaps in our understanding, as most studies focus on just one type of stressor. Thus, we set out to investigate potential ecological, social and reproductive sources of stress and their relative impact on the endocrine stress response, measured via fecal glucocorticoid metabolites. To do so we collected data on social behavior, food abundance and intake along with hormonal data on physiological stress on all adult females of a group of wild Assamese macaques at Phu Khieo Wildlife Sanctuary. In a first step we investigated social effects on the physiological stress response and found significant seasonal differences in same and opposite sex social interaction patterns which in turn predicted fecal glucocorticoid output (Fürtbauer et al. 2014). Specifically, in the non-mating season when females mainly associated with females and only infrequently with males, female-female affiliation predicted lower stress levels, whereas during the mating season male-female interaction rates and patterns predicted fecal glucocorticoid levels (Fürtbauer et al. 2014). These results indicate i) that opposite just as well as same sex social interactions can attenuate the stress response and ii) that their relative importance may fluctuate with seasonal or life stage specific needs. In a next step we will combine nutritional, behavioral and reproductive data to investigate their relative influence on stress physiology in wild macaque females (I. Fürtbauer, O. Schülke, M. Heistermann, J. Ostner, unpubl, data). Publication plans The first set of results covering the effects of same and opposite sex sociality on the physiological stress response has recently been published (Fürtbauer et al. 2014). The further aim of this project, i.e. disentangling nutritional reproductive and psychosocial sources of stress will be prepared for submission in the next months. The final step will be to combine data on the sources of stress, physiological stress levels and health outcome into one comprehensive picture. Project Overview This study aimed to investigate and unravel potential ecological, psychosocial, and reproductive sources of stress and their relative impact on the endocrine stress response, i.e. fecal glucocorticoid (fGC) output, in wild female Assamese macaques (Macaca assamensis) living at Phu Khieo Wildlife Sanctuary, Northeastern Thailand. It specifically centered around three main objectives: first, we aimed to disentangle the ecological, social and reproductive sources of physiological stress employing a multivariate approach and data on individual energy intake, reproductive status and social factors. Second, we aimed to investigate how social factor would influence an individual’s stress response and coping mechanisms. Finally, we aimed to investigate the physiological costs and possible benefits females experience when being consorted by males. The project capitalized on a dataset consisting of more than 2000 hours of focal observations and 2558 fecal samples for 1