Increases in fecal testosterone precede increases in fecal dehydroepiandrosterone in wild male mountain gorillas (Gorilla beringei beringei).

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 rises afterwards at 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.