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.

《生物多样性公约》和国际自然保护联盟强调异地保护工作是不可避免的。然而，管理不当或物种生理学知识不足会导致易地种群的压力行为迹象和低繁殖成功率。我们在圈养的Brachyteles arachnoides 中评估了 12 个月的粪便类固醇。我们收集了生活在三个不同群体中的五名男性和三名女性的数据。我们将生殖行为与女性雌激素和孕激素代谢物水平的数据以及男性睾酮 (fTM) 和糖皮质激素 (fGCM) 代谢物水平的数据相结合。对于女性，我们检测到排卵、怀孕和分娩后卵巢活动的恢复。此外，所有女性在晚春期间都是非周期性的，暗示着季节性。在雄性中，我们没有观察到 fTM 或 fGCM 的年度变化，但饲养在一起的雄性表现出较高的 fGCM 和较低的 fTM，交配较少，并且比孤立的雄性或单雄性多雌性组中的雄性更具攻击性。这些结果表明B.arachnoides表现出与生殖竞争一致的特征。通过将其特定的生殖行为纳入管理实践指南，我们不仅可以防止俘虏个体可能发生的打架、受伤和死亡，还可以增加他们的福利和繁殖成功率。