Variation of glucocorticoid metabolite levels is associated with survival demands in immature and reproductive demands in adult wild black capuchins (Sapajus nigritus)

Abstract

According to the concept of allostasis and its association with energy mobilization, glucocorticoids (GCs) should parallel cumulative energy expenditure for animal survival and reproduction. Therefore, it is expected that seasonal food shortages might lead to increased levels of GCs. We tested this hypothesis by analyzing the intra-annual variation of fecal glucocorticoid metabolites (GCM) in 14 wild black capuchin monkeys (Sapajus nigritus) living in a social group in the Brazilian Atlantic Forest. We analyzed the association between GCM and social and environmental variables for the three age/sex classes (adult males, adult females and immatures [juveniles and infants]). Decreased fruit intake during the dry season increased the GCM levels of both immatures and adult males. Although fruit shortage influenced the allostasis of adult males, the variation in their GCM levels was more impacted by the breeding season. GCM levels of adult females varied during the late stage of pregnancy. These results suggest fruit consumption as the main source of allostatic load for immature animals, while reproductive costs had greater effect on adults.