Doctoral Dissertation Improvement: Social and Hormonal Mechanisms of Male Reproductive Skew in Black Howler Monkeys (Alouatta pigra)

这项为期12个月的研究将调查墨西哥帕伦克国家公园两群黑吼猴（Alouatta pigra）雄性繁殖分配的社会和激素机制。具体而言，pi将通过对所有成年部队成员进行系统的焦点样本，检查雄性社会互动与粪便睾丸激素和皮质醇水平之间的关系，以评估雄性生殖策略是否与其睾丸激素和皮质醇水平相关。了解这些关系将为了解灵长类动物社会和性行为的生物学基础提供有价值的见解。在多雄性灵长类动物群体中，雄性的繁殖分布可以是高度倾斜的，当一个雄性在其居住期间垄断了所有的繁殖机会，而当繁殖在一个群体中的雄性之间分布更均匀时，这种倾斜程度就会降低。有一个以上繁殖活跃雄虫的群体可能是由于(1)优势雄虫无法排除其他雄虫的繁殖（拔河模型），或者(2)优势雄虫将繁殖机会让给从属雄虫作为一种持续的激励，优势雄虫通过增加繁殖成功率从从属雄虫的存在中获益（让步模型）。虽然对几种野生灵长类动物的父权研究已经证实了雄性优势等级与繁殖成功率之间的正相关关系，但影响繁殖偏态的直接机制尚不清楚。挑战假说认为，循环睾酮浓度的时间变化与男性在生殖环境中的攻击性模式有关，并结合社会等级和个体应激反应模式之间的关系（通过皮质醇水平测量），为研究男性生殖偏态机制的关键组成部分提供了一个新的框架。pi还将收集关于背吼雄性之间亲缘关系的数据，以进一步了解亲属关系对雄性之间合作和竞争互动水平及其生殖策略的影响。雌性的配偶选择应该通过影响优势雄性垄断受精的能力来影响雄性的生殖倾斜。pi将使用粪便黄体酮和雌二醇谱来确定其卵巢周期的时间，然后将男性和女性的性请求和拒绝映射到这些周期中，以评估女性是选择只与优势男性交配，还是在整个生育期与多个男性交配，或者与多个男性交配，除了在排卵期，当受孕更容易发生。这项研究将建立在灵长类社会进化的既定理论的基础上，假设雄性社会互动是合作与竞争之间的平衡。该研究和分析将由研究生进行博士论文研究，从而推进NSF的教育和培训任务。这种濒危灵长类动物的种群保护计划也将受益，因为这项研究将允许对连续栖息地和破碎栖息地的社会变量和激素变量进行比较。这项研究将通过墨西哥大学生的参与来加强当地的能力建设。

This 12-month study will investigate the social and hormonal mechanisms underlying the partitioning of reproduction among males in two troops of black howler monkeys (Alouatta pigra) at Palenque National Park, Mexico. Specifically, the PIs will examine the relationships between male social interactions and fecal testosterone and cortisol levels using systematic focal samples on all adult troop members to assess whether male reproductive strategies correlate with their testosterone and cortisol levels. Understanding these relationships will provide valuable insights into the biology underlying primate social and sexual behavior. The distribution of reproduction among primate males in multimale groups can range from highly skewed, when one male monopolizes all reproductive opportunities during his residence, to less skewed when reproduction is more evenly distributed among males in a group. Groups with more than one reproductively active male could result from either (1) the inability of the dominant male to exclude other males from reproducing (tug-of-war model), or (2) the dominant male's concession of reproductive opportunities to subordinate males as a staying incentive, with the dominant male benefiting from the presence of subordinate males through increased reproductive success (concession model). While paternity studies in several wild primates have confirmed a positive relationship between male dominance rank and reproductive success, the proximate mechanisms that affect reproductive skew are not yet understood. The challenge hypothesis, which posits that temporal variation in circulating testosterone concentrations is related to patterns of male aggression in reproductive contexts, combined with the relationship between social rank and patterns of individual stress response measured via cortisol levels, provides a new framework for investigating key components of the mechanisms of male reproductive skew. The PIs will also gather data on relatedness among back howler males to gain further insights into the influence of kinship on levels of cooperative and competitive interactions among males and their reproductive strategies. Female mate choice should influence male reproductive skew through its effects on the dominant male's ability to monopolize fertilizations. The PIs will use fecal progesterone and estradiol profiles to determine the timing of their ovarian cycles, and then map male and female sexual solicitations and rejections onto these cycles to evaluate whether females choose to mate exclusively with dominant males, with multiple males throughout their fertile periods, or with multiple males except during their periovulatory periods, when conceptions are more likely to occur.The study will build on established theories of the evolution of primate sociality positing that male social interactions are a balance between cooperation and competition. The research and analyses will be conducted by a graduate student for her doctoral dissertation research, thereby advancing the educational and training mission of the NSF. Conservation programs for populations of this endangered primate will also benefit because the study will permit a comparison between social and hormonal variables in continuous versus fragmented habitats. The study will enhance local capacity building through the participation of Mexican university students.