Population ecology of arctic birds and mammals in a changing climate

营养相互作用在控制动物种群中的作用仍然存在争议，特别是在北极生态系统中。然而，极地地区气候变暖的快速步伐极有可能破坏物种相互作用并影响其种群动态，特别是对循环种群或被人类利用的物种（如被猎杀的物种）。我的研究计划的目的是提高我们对北极鸟类和哺乳动物种群动态的基本认识，并确定控制种群的因素，特别是营养相互作用，将如何随着气候变暖而变化。在接下来的5年里，我将研究(1)捕食在北极产生种群周期中的作用；(2)季节性作为种群周期的潜在驱动力；(3)雪和动物人口统计学之间的相互作用；(4)环境变化如何影响被开发物种狩猎和自然死亡之间的平衡。首先，我将通过实验验证这样一个假设，即捕食可以通过直接（捕食造成的死亡）和间接影响（应激激素介导的母体对生殖的影响）的组合来产生旅鼠种群周期。这将通过使用大规模操作（在大型围栏上排除捕食者）测量旅鼠人口统计学和生理学来实现。其次，我将通过测量冬季繁殖季节的长度和模拟冬季繁殖对种群增长的影响来检验旅鼠人口统计的特殊季节性（冬季繁殖力高，死亡率低）是否可能是种群周期的驱动因素。第三，据报道，在冬季变暖的地区，旅鼠周期的崩溃可能是由于雪况的变化。我将研究气象条件、雪的物理特性和冬季繁殖之间的联系，以便建立一个模型，根据积雪的情况预测每年旅鼠的数量。第四，评估人类开发与环境条件变化之间的相互作用如何影响候鸟种群动态。我将通过长期的捕获-标记-再捕获研究来研究营养不匹配如何在幼雪雁的特定原因死亡率（狩猎与自然原因）之间切换平衡。当植物物候对气候变暖的反应比食草动物更快时，就会出现不匹配，这对食草动物的繁殖产生了负面影响。本研究项目将培养7名研究生和10名本科生。这将有助于范式转变，即在广泛的生态系统中，捕食正在成为控制动物种群的主导力量。通过结合实证和建模研究，我还将提供工具，对野生动物种群的未来变化做出定量预测，以应对快速变化的环境。

The role of trophic interactions in controlling animal populations remains controversial, especially in Arctic ecosystems. Yet, the rapid pace of climate warming in Polar regions has a strong potential to disrupt species interactions and affect their population dynamic, especially for cyclic populations or those exploited by humans such as hunted species. The aim of my research program is to improve our fundamental understanding of the population dynamic of arctic birds and mammals and to determine how factors controlling populations, especially trophic interactions, will change with climate warming. Over the next 5 years I will study (1) the role of predation in generating population cycles in the Arctic, (2) seasonality as a potential driving force of population cycles, (3) the interaction between snow and animal demography and (4) how environmental change can affect the balance between hunting and natural mortality in exploited species. First, I will test experimentally the hypothesis that predation can generate lemming population cycles through a combination of direct (mortality from predation) and indirect effects (maternal effects on reproduction mediated by stress hormones). This will be achieved by measuring lemming demography and physiology using a large-scale manipulation (predator exclusion over a large fenced plot). Second, I will examine whether the peculiar seasonality of lemming demography (high fecundity and low mortality in winter) may be a driver of population cycles by measuring the length of the winter breeding season and modelling the effect of winter breeding on population growth. Third, a collapse of lemming cycles has been reported in areas where the winter has warmed, possibly due to changing snow condition. I will study the links between meteorological conditions, snow physical properties and winter reproduction in order to develop a model that could predict annual lemming abundance based on conditions of the snow pack. Fourth, I will assess how the interaction between human exploitation and changing environmental conditions can affect the population dynamic of migratory birds. I will examine how trophic mismatch can switch the balance between cause-specific mortalities (hunting vs natural causes) in young snow geese using a long-term capture-mark-recapture study. A mismatch occurs when plant phenology respond more quickly to climate warming than herbivores, which negatively affects herbivore reproduction. This research program will provide training for 7 graduate and 10 undergraduate students. It will contribute to a paradigm shift where predation is emerging as a dominant force controlling animal populations in a wide range of ecosystems. By combining empirical and modelling studies, I will also provide tools to generate quantitative predictions on future changes in wildlife populations in response to a rapidly changing environment.