Effects of progressing age on energy balance, sociality and health in wild female Assamese macaques (Macaca assamensis)

随着人类年龄的增长，他们的社交活动减少，在选择伴侣时也变得越来越挑剔，更喜欢有价值的关系，而不是没有意义的关系。这种社会情感的选择性被归因于老年人有限的时间视角。社交活动和社交伙伴数量的减少也是非人灵长类动物在缺乏有限时间意识的情况下年龄增长的特征。我们认为，随着年龄的增长，社会活动的减少是由于觅食性能、能量摄入和能量平衡的年龄相关的能量限制所驱动的。精力限制和社交减少构成精力和社会压力源，预计会影响生理压力水平，进而影响个人健康。在这个长期研究野生阿萨姆猕猴种群的项目中，我们将年龄对食物摄入和能量收支的影响、社会整合的措施、营养和社会压力的生理措施与健康指标（特别是肠道微生物群落和非特异性免疫标志物）的数据结合起来。这个项目有三个主要目标。首先，我们将增加自然生态条件下野生种群行为老年学的少数研究，使我们能够整合能量约束作为限制社会活动的重要但很少被研究的因素。其次，我们的目标是通过同时测量非特异性应激标志物（糖皮质激素）和营养应激标志物（甲状腺激素）来分离老年人对营养和社会应激源的生理反应。最后，我们的目标是将年龄相关的能量限制、生理应激反应和社会融合措施与健康指标联系起来。总之，这些数据将有助于全面了解能量因素对社会活动和年龄增长的选择性的作用，并将为人类行为老年学的研究提供信息。

As humans age they decrease their social activity and become increasingly selective in their choice of partners favoring valuable relationships over less meaningful ones. This socio-emotional selectivity has been attributed to the limited time perspective of elderly humans. A decline in social activity and number of social partners are also characteristics of increasing age in nonhuman primates in the absence of awareness of limited time. We propose that the declining social activity with progressing age is driven by energetic constraints due to age-related decreases in foraging performance, energy intake and energy balance. Energetic constraints and decreasing sociality pose energetic and social stressors and are expected to influence physiological stress levels which in turn impact an individual´s health. In this project on our long-term study population of wild Assamese macaques facing pronounced natural variation in energy availability, we combine data on age effects on food intake and energy budget, measures of social integration, physiological measures of nutritional and social stress with indicators of health, specifically the gut microbial community and a non-specific immune marker. This project has three main goals. First, we will add to the few studies on behavioral gerontology in wild populations under natural ecological conditions which enables us to integrate energetic constraints as an important but rarely investigated factor limiting social activity. Second, we aim to separate physiological responses to nutritional and social stressors experienced by aged individuals by simultaneously measuring a non-specific stress marker (glucocorticoids) and a nutritional stress marker (thyroid hormone). Lastly, we aim to link age-related energetic constraints, physiological stress responses and measures of social integration to health indicators. Together, these data will contribute to a comprehensive understanding of the role of energetic factors on social activity and selectivity with increasing age and will inform studies on human behavioral gerontology.