Socioendocrinology of Cooperative Offspring Care

雌性单独照顾后代是哺乳动物的常态，但在一小部分物种中，雄性和其他群体成员在抚养依赖后代方面也发挥着重要的、潜在的关键作用。在狨猴和绢毛猴这些新世界的灵长类动物中，所有群体成员，包括母亲、父亲、非繁殖的幼崽和亚成虫，都照顾它们，这是社会群体的常态。NSF之前的研究结果显示，母亲和父亲在照顾婴儿方面的努力程度存在重大差异，母亲在婴儿出生后的前两周在照顾婴儿方面发挥了重要作用，而父亲和助手在婴儿出生后的第三周和第四周及以后发挥了核心作用。这些变化与母亲和父亲睾酮(T)浓度的变化有关：母亲的睾酮在产后前两周减少，父亲的睾酮在产后后两周减少，这与婴儿护理率最高相对应。当前提案中概述的研究将利用观察和实验两种方法来研究睾酮浓度的变化是否有助于调节狨猴对婴儿的反应性，以及睾酮是否调节了婴儿护理与生殖和/或攻击行为之间的权衡，这可能与婴儿护理不相容。这一结果将揭示社会性灵长类动物复杂的亲和和照料行为可能部分地受到生物状态和经验相关因素的影响。

Exclusive offspring care by females is the norm among mammals, but among a small set of species, males and other group members also play an important and potentially crucial role in the nurturing of dependent offspring. Among marmosets and tamarins, primates of the New World, care by all group members, including the mother, father, and nonbreeding juveniles and subadults, is the norm for social groups. Results from previous NSF funding have revealed important differences in levels of effort in infant care by mothers and fathers, with mothers playing a large role in infant care in the first two weeks of life, and fathers and helpers playing a central role in the 3rd and 4th weeks of infant life and beyond. These changes are associated with variations in testosterone (T) concentrations in mothers and fathers: T is reduced in mothers in the first 2 weeks post partum and in fathers during the second 2 weeks post partum, which corresponds to the highest rates of infant care. The studies outlined in the current proposal will utilize both observational and experimental approaches to the possibility that variation in testosterone concentrations helps regulate responsiveness to infants in marmosets, and whether T mediates a trade-off in effort in infant care versus reproductive and/or aggressive behaviors, which may be incompatible with infant care. The results will shed light on the possibility that complex affiliative and caregiving behaviors in social primates may, in part, be influenced by biological states, as well as experience-related factors.