Effect of stress on profiles of fecal glucocorticoid and androgen metabolites and antler status in marsh deer (Blastocerus dichotomus)

Abstract

The influence of glucocorticoids on reproductive hormones and antler cycles in cervids remains poorly understood, particularly in tropical species. Most Neotropical deer, like the marsh deer (Blastocerus dichotomus), lack a defined breeding season or a clear link between antler stage and reproductive status. Furthermore, conflicting data regarding stress impacts on androgen levels and antler development underscore the need for further research. We evaluated the effects of stress on fecal glucocorticoid metabolites (FGMs), fecal androgen metabolites (FAMs) and antler status in captive marsh deer. Nineteen males underwent a quarantine after being transferred to a new breeding site, with antler status monitored weekly. Daily fecal samples from 17 individuals were analyzed using EIA to measure FAM and FGM concentrations. Among 12 animals with fully developed antlers, nearly 60 % (n = 7) experienced antler casting, an unusual synchrony for this species. A positive correlation was found between FAM and FGM levels (p < 0.001; r = 0.40). We compared FAM and FGM levels between juveniles and adults, as well as among the antler categories. Adults exhibited 1.2-fold higher FGM levels than juveniles, with no differences in FAM levels. Males with hard antlers showed the highest FAM levels, while FGM levels were highest in males with velvet antlers. We hypothesize that intense stress negatively affected antler retention, leading to antler casting. Our findings suggest that stressful stimuli may trigger adrenal secretion of glucocorticoids and androgens, providing insights into the relationship between stress and antler dynamics in marsh deer.