Publications [#219081] of Steffen Foerster

Papers Published

1. Foerster, S. and Cords, M. and Monfort, S.. "Metabolic but not psychological stressors modulate temporal and inter-individual variation in fecal glucocorticoid levels among wild female Cercopithecus mitis in two Kenyan populations." American Journal of Primatology 72.S1 (2010): 73.
   (last updated on 2013/10/07)

   Abstract:
   As important mediators of physiological stress responses, glucocorticoids can be used to assess the fitness consequences of environmental and behavioral variation in wild vertebrates. We summarize results from a study that investigated the relative contributions of daily life psychological and metabolic stressors to modulating fecal glucocorticoids (fGCs) in 32 wild female blue and Sykes' monkeys (Cercopithecus mitis) in three social groups inhabiting two forested sites in Kenya. We collected >5,700 fecal samples and >6,000 hours of behavioral data over one year. We analyzed temporal variation with general linear mixed models, investigated interaction terms in posthoc analyses, and used non-parametric statistics to assess the correlates of individual differences. Results were considered significant if P<0.05. While in any month fGCs were higher for pregnant than non-pregnant, non-lactatingfemales, changes across months were indistinguishable for both classes of females. Females excreted more GCs when the availability of high quality food was low, while agonistic and affiliative interactions had no influence on temporal GC variation. Similarly, inter-individual differences in fGCs were best explained by exposure to metabolic, not psychological stressors. When resource access was skewed towards high-ranking females, low-ranking females showed elevated fGCs. Overall, evidence suggests that despite the tropical forest environment and dietary flexibility, metabolic challenges may influence life history parameters such as timing of infant independence and interbirth intervals, providing potential fitness benefits to high-ranking females.