Reproductive and Stress Response Hormones of the Critically Endangered Southern Muriqui ( Brachyteles arachnoides : Atelidae) Under Captive Conditions

The Convention on Biological Diversity and the International Union for Conservation of Nature emphasize that ex situ conservation efforts are unavoidable. However, inappropriate management or insufficient knowledge of species physiology can lead to behavioral signs of stress and low breeding success in ex situ populations. We assessed fecal steroids across 12 months in captive Brachyteles arachnoides. We collected data on five males and three females living in three different group compositions. We combined reproductive behavior with data on estrogen and progestin metabolite levels in females, and with testosterone (fTM) and glucocorticoid (fGCM) metabolite levels in males. For females, we detected ovulations, pregnancy, and resumption of ovarian activity following parturition. Additionally, all females were acyclical during late spring, suggestive of seasonality. In males, we did not observe annual variation in fTM or fGCM, but males housed together showed higher fGCM and lower fTM, copulated less, and were more aggressive than an isolated male or a male in a unimale—multifemale group. These results suggest that B. arachnoides presents traits consistent with reproductive competition. By including its particular reproductive behavior in management practice guidelines, we can not only prevent possible fights, injuries, and death of captive individuals, but also increase their welfare and reproductive success.