A direct test of the impact of infection on animal migration: consequences for parasite and host populations

野生动物种群经历了广泛的感染，既可能影响自己的健康，也可能跨越物种边界，对农场动物和人类健康构成环境风险。这种感染的影响将与物种的运动生态密不可分，因为动物在其环境中移动的方式是决定感染如何传播和持续的主要因素。因此，预测感染动态并减轻其影响需要了解感染如何影响动物运动，进而了解动物运动对感染动力学的影响。因此，我们将在这个项目中解决三个关键问题：1)感染状况是否影响个体的迁徙策略？2)感染是否在不同程度上影响候鸟和居民的生存和繁殖成功？3)迁徙行为的差异是否会扩大到影响宿主种群的感染水平。我们将在部分迁徙的海鸟种群中调查这些问题，这些海鸟在苏格兰东南部的梅岛国家级自然保护区繁殖，但沿英国东海岸迁徙。最近的理论研究模拟了三种与疾病相关的机制，这些机制可能直接影响对迁徙的选择或反对。这是迁徙逃逸，迁徙使个体逃离高暴露的栖息地或受感染的个体。2)迁徙恢复，即受感染的个体迁徙到不同的地区，以获得促进恢复的资源3)迁徙扑杀，受感染的个体在迁徙期间遭受更高的死亡率。我们将首先测试自然的寄生虫水平是否与个体在生命第一年表现出的迁徙策略有关，以及随后成为居民或迁徙的青少年的免疫措施是否不同。然后，我们将通过实验减少寄生虫的负担来实验测试寄生虫是否具有因果作用。然后，我们将测试寄生虫是否与候鸟和居民在繁殖成功和生存方面的差异有关。我们将使用多年的人口统计数据将个体的迁徙策略与寄生虫的水平和适合度的组成部分联系起来，以测试a)寄生虫是否与任何潜在的迁移选择优势有关，以及b)这种优势可能通过的人口统计途径。最后，我们将测试几年间寄生虫种群水平的变化是由于个体从感染中恢复时个体寄生虫负担的减少，还是由于个体从感染中恢复时种群中受感染宿主的损失。从管理或保护的角度来看，这一点很重要，因为这些替代解释将导致关于种群对感染的稳健性的截然不同的结论。因此，这项研究将首次对寄生如何推动部分迁徙物种的迁徙运动进行联合测试，测量寄生虫丰度对种群水平变化的影响，以及这些结果是否源于高水平的宿主死亡率。这些是评估迁徙对环境中寄生虫持久性的影响以及寄生虫对动物种群不同组成部分的影响的关键。

Wildlife populations experience a wide range of infections that can both impact on their own health and cross species boundaries to pose environmental risks to farm animal and human health. The impact of this infection will be inextricably linked to a species' movement ecology, as the way in which animal movements around their environment is a major factor in determining how infections are transmitted and persist. Predicting infection dynamics and mitigating their impacts therefore requires understanding how infection influences animal movements and, in turn, understanding the consequences of animal movement for infection dynamics. We will therefore address three key questions in this project: 1) Does infection status influence individual migration strategy? 2) Does infection affect the survival and breeding success of migrants and residents to different extents? 3) Do differences in migratory behaviour scale up to affect levels of infection in host populations.We will investigate these questions in a partially migratory population of seabirds that breed on the Isle of May National Nature Reserve in South East Scotland but migrate along the East Coats of the UK. Recent theoretical studies have modelled three disease related mechanisms that could directly affect selection for, or against, migration. These are 1) migratory escape, whereby migration allows individuals to escape from high-exposure habitats or infected individuals. 2) migratory recovery, whereby infected individuals migrate to a different area to gain resources that facilitate recovery 3) migratory culling, whereby infected individuals suffer higher mortality during migration.We will firstly test whether natural levels of parasitism are associated with individual migration strategy expressed in an individual's first year of life and whether measures of immunity differ in juveniles that subsequently become resident or migrant. We will then experimentally test whether parasitism has a causal role through experimental reduction of parasite burden.We will then test whether parasitism is associated with differences in breeding success and survival of migrants and residents. We will use multi-year demographic data to link individual migration strategy to levels of parasitism and components of fitness to test a) whether parasitism is associated with any potential selective advantage of migration and b) the demographic routes through which this may operate.Finally we will test whether changes in population levels of parasitism between years is due to decreases in individual parasite burden as individuals recover from infection or the loss of infected hosts from the population as they fail to survive. This is important from a management or conservation point of view as these alternative explanations would lead to very different conclusions about the robustness of the population to infection.This study will therefore provide first combined test of how parasitism drives migratory movements in a partially migratory species with measuring the consequences for population level changes in parasite abundance and whether these result from high levels of host mortality. These are key to assessing the impact of migration on parasite persistence in the environment and the impact of parasitism on different components of animal populations.