Happy low, lie down!

High-ranking animals typically enjoy preferential access to important resources, such as food, water, safe foraging and sleeping sites, and social support. Consequently, high status is normally expected to have positive effects on health and longevity. However, growing evidence suggests that, across vertebrates, such effects are more common among females. High-ranking males often invest heavily in aggressive competition, incurring a range of costs. In a new study, just published in Hormones and Behavior, a team led by Martin Muller looked at glucocorticoid (GC) measures in >8000 urine samples collected from 20 adult male chimpanzees over 20 yrs. Cumulative exposure to GCs is often used as a measure of wear and tear on an organism, and is negatively associated with survival in long-lived species. In Kanyawara males, both instability in the dominance hierarchy and competition over estrous females increased GC production. However, high-ranking males had elevated GCs regardless of hierarchy stability or the presence of estrous females. Involvement in aggression was the key mechanism linking high rank with GC production. These results show that investment in male-male competition increases cumulative exposure to GCs in chimpanzees, suggesting a long-term tradeoff with health that may constrain the ability to maintain high status across the life course. They also suggest a broader sex difference in the effects of status striving and mating effort on health that deserves further attention.

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