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Abstract Testosterone (T) and dehydroepiandrosterone sulfate (DHEAS) are two steroids integral to male primate development. For humans, both are high in early infancy (for T, this is known as minipuberty) then rapidly decline. DHEAS then increases beginning in early childhood, resulting in a process known as adrenarche, which signals the maturation of the zona reticularis of the adrenal gland. T increases a few years thereafter, marking the beginning of puberty. These processes are relatively well-studied in humans, but data is lacking for the other great apes. Particularly for adrenarche, strikingly little is known about its distribution across the primate order. Here, we draw on a large sample of wild male mountain gorilla fecal samples collected over the full course of the gorilla lifespan to examine how the hormones T and DHEAS change with age. We use enzyme-linked immunosorbent assays to quantify metabolites of both hormones, and validate these assays using high-performance liquid chromatography–tandem mass spectrometry analyses. We find that both hormones are high in male gorilla infancy, and then decline before T rises again at 9.3 years of age. Surprisingly, DHEAS risesafterwardsat 10.7 years old, showing a departure from the human developmental pattern. T then peaks at 18 years of age, while DHEAS plateaus at ~ 23 years of age. More research is needed to assess intra-order variation in primate hormonal development. 

The Challenge Hypothesis is an influential framework for understanding how androgens are involved in the promotion of competitive behavior during mating-related challenges and has been tested extensively in studies across scientific disciplines. Mixed support in psychological research led scholars to develop the Dual Hormone Hypothesis as a potential path forward, which argues that glucocorticoids moderate the relationship between androgens and status-striving. In the current study, we examine the Challenge Hypothesis and the Dual Hormone Hypothesis in wild male mountain gorillas, representing the first time the latter hypothesis has been tested in a non-human primate. In a sample of 30 adult males comprising over 600 days of observation, we find some limited support for the Challenge Hypothesis. Greater daily rates of targeted aggression toward other adult males corresponded to higher fecal androgen metabolites 1–2 days following observations, though this pattern did not fully generalize to dominance rank or other competitive behaviors examined. However, we find no support for the Dual Hormone Hypothesis: neither dominance rank nor any category of competitive behavior was predicted by the interaction between androgens and glucocorticoids. We close by discussing how this initial investigation might be leveraged toward the development of an expanded Dual Hormone Hypothesis that draws on the large evidence base in primate behavioral ecology.