Steffen Foerster

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Because of their mediating role in the stress response and potential effects on fitness, glucocorticoid (GC) hormones are increasingly used to assess the physiological costs of environmental and behavioral variation among wild vertebrates. Identifying the proximate causes of GC variation, however, is complicated by simultaneous exposure to multiple(More)
Animals facing seasonal variation in food availability experience selective pressures that favor behavioral adjustments such as migration, changes in activity, or shifts in diet. Eclectic omnivores such as many primates can process low-quality fallback food when preferred food is unavailable. Such dietary flexibility, however, may be insufficient to(More)
In most primate societies, strong and enduring social bonds form preferentially among kin, who benefit from cooperation through direct and indirect fitness gains. Chimpanzees, Pan troglodytes, differ from most species by showing consistent female-biased dispersal and strict male philopatry. In most East African populations, females tend to forage alone in(More)
Dominance hierarchies are widespread in animal social groups and often have measureable effects on individual health and reproductive success. Dominance ranks are not static individual attributes, however, but instead are influenced by two independent processes: 1) changes in hierarchy membership and 2) successful challenges of higher-ranking individuals.(More)
Animal sociality facilitates the transmission of pathogenic microorganisms among hosts, but the extent to which sociality enables animals' beneficial microbial associations is poorly understood. The question is critical because microbial communities, particularly those in the gut, are key regulators of host health. We show evidence that chimpanzee social(More)
OBJECTIVE When resource competition within primate social groups is effective, high-ranking individuals generally gain fitness benefits. Contrary to expectations, female Cercopithecus mitis form linear dominance hierarchies without evidence for rank-related variation in fitness-relevant measures, raising questions about the evolution of guenon social(More)
Although rarely observed, predation is thought to be an important factor in the evolution of primate life histories and behavior. Here I describe two incidents of snake predation on Cercopithecus mitis guenons from Kenya. The first case involved a juvenile blue monkey (Cercopithecus mitis stuhlmanni) in the Kakamega Forest, which died following a bite by a(More)
Socioecological theory predicts that aggressive feeding competition is associated with linear dominance hierarchies and reproductive advantages for high-ranking females. Female blue monkeys contest fruits and have a linear dominance hierarchy, yet previous research has shown no evidence that high-ranking females benefit from greater feeding success or(More)
Hunted wild animals (i.e., bushmeat) are a main source of protein for many rural populations in the tropics, and the unsustainable harvest of these animals puts both human food security and ecosystem functioning at risk. To understand the correlates of bushmeat consumption, we surveyed 1219 households in 121 rural villages near three newly established(More)