EAGER: Modeling Coupled Herd and Household Dynamics in Pastoral Systems

人类学家用“畜牧业”一词来指依赖饲养牲畜的经济。长期以来，畜牧业一直被认为是生活在生产力较低、自然资源较少的环境中的人们的一种良好战略。然而，即使是牧民也不得不考虑如何平衡他们饲养的动物数量与可供喂养它们的牧场和可用于照顾它们的劳动力。事实上，种群模型表明，牲畜种群有可能成倍增长，超过其环境的承载能力。但经验证据表明，情况并非如此：在真实的世界中，牧区牲畜数量相对稳定。问题是如何实现这种平衡？到目前为止，最流行的解释是干旱、疾病和其他灾害控制了牲畜数量。但该奖项支持的研究将测试另一种解释：人口动态-随着时间的推移家庭规模的自然扩张和收缩-在畜群和家庭层面的运作可能会限制区域牲畜数量的增长。如果情况确实如此，正如这个跨学科研究小组所提出的那样，那么它对牧区社会的发展干预具有影响。改善兽医健康和减少干旱脆弱性将改善牧民的生活，而不一定威胁自然资源基础。 该研究小组将开发一个基于代理人的模型，以研究家庭的家庭周期对家庭畜群的人口统计的影响，并最终对区域牲畜种群。从以前的研究经验数据将被用来参数化的代理为基础的模型。该模型将模拟100户家庭的初始人口的家庭周期及其家庭畜群250年（或10代）的人口统计过程。这些模拟将使研究人员能够通过研究初婚年龄变化、儿子数量增加或一夫多妻率增加的影响，来研究家庭周期如何影响牛群人口统计。此外，模拟将用于研究区域牲畜种群的增长对牲畜规模阈值变化的敏感程度，即，较低的阈值是否会导致区域一级牲畜数量的更大增长。这项研究的结果将为畜牧社会的牲畜种群动态提供深入了解，特别是为什么这些种群在没有干旱和疾病等重大灾害的情况下似乎没有增加的问题。

Anthropologists use the term "pastoralism" to refer to economies that depend on raising livestock. Pastoralism has long been viewed as a good strategy for people who live in less productive environments with few natural resources. However, even pastoralists have to be concerned about balancing the number of animals they keep with the pasture available to feed them and the labor available to care for them. Indeed, population models show that livestock populations have the potential to grow exponentially and oustrip the carrying capacity of their environments. But empirical evidence indicates otherwise: in the real world, pastoral livestock populations are relatively stable. The question then is how is this balance achieved? Until now the most popular explanation has been that droughts, diseases, and other disasters keep livestock populations in check. But the research supported by this award will test an alternative explanation: demographic dynamics -- the natural expansion and contraction of family sizes over time -- operating at the herd and household level may constrain the growth of livestock populations regionally. If this is indeed the case, as this interdisciplinary research team proposes, then it has implications for development interventions in pastoral societies. Improving veterinary health and reducing drought vulnerability would then improve the lives of pastoralists without necessarily threatening the natural resource base. The research team will develop an agent-based model to examine the impact of the domestic cycle of households on the demography of family herds and ultimately on regional livestock populations. Empirical data from previous studies will be used to parameterize the agent-based model. The model will simulate the domestic cycle of an initial population of 100 households and the demographic processes of their family herds for 250 years (or 10 generations). The simulations will allow the researchers to examine how the domestic cycle affects herd demography by examining the impact of changes in age of first marriage, increase in the number of sons, or increase in polygyny rates. In addition, the simulations will be used to examine how sensitive the growth of regional livestock populations is to changes in the herd-size threshold, i.e., whether a lower threshold leads to stronger growth of livestock populations at the regional level. Findings from this research will provide insight into livestock population dynamics in pastoral societies, in particular the question of why these populations do not seem to increase in the absence of major disasters like droughts and diseases.