Revealing the hidden effects of anthropogenic disturbance on the spatiotemporal dynamics of animal populations

在全球范围内，由于人类活动施加的压力不断增加，自然生态系统受到威胁。许多生态系统正在变得支离破碎或在边缘被侵蚀，而人类干扰的影响甚至在保护区的核心也能感受到。通常，人类活动或人为改变环境的影响是显而易见的：当自然栖息地被破坏时，无法逃脱的动物将会死亡；人类通过偷猎、狩猎或捕鱼等方式直接收获野生动物；风力涡轮机或道路等基础设施会导致动物死亡的碰撞；虽然疾病可以从牲畜传播并大量杀死野生种群。除了这些直接影响，许多研究表明，人类如何对动物产生更微妙的影响。例如，人类活动可以诱发回避行为，限制进入重要的觅食区域，增加压力和警戒水平，并通过向环境中引入噪音和光线来干扰感觉机制。虽然不那么明显，但这些间接影响可能会产生很大的影响，因为许多动物在其生理极限的边缘活动，因此它们的能量需求与资源的可用性是精细平衡的，身体虚弱的个体可能很快就会屈服于捕食者、寄生虫或疾病。这意味着，即使是人类活动的微小影响也会大大降低动物生存和繁殖的可能性，这反过来又会导致种群数量的突然大幅下降。在这项研究中，我们将调查日益增加的人类压力对角马迁徙种群的影响，角马是栖息在东非大塞伦盖蒂生态系统的关键物种。我们将评估人类干扰如何改变动物的运动方式，它们花费多少时间消耗资源而不是保持警惕，以及这些因素如何影响它们的身体状况。我们将测试这些影响是否会改变个体的生存概率以及它们拥有可存活后代的机会。为了评估人类干扰对运动和活动的影响，我们将使用安装在迁徙角马项圈上的GPS设备和活动传感器，并结合对资源分布（植被和土壤养分图）和风险（人类基础设施、旅游、非法狩猎活动和自然捕食的位置）的全面描述。GPS项圈和传感器将使我们能够跟踪动物，并确定它们对这些环境特征的反应，包括它们在空间中的移动方式，以及它们分配给不同活动的时间。为了评估身体状况如何影响生存和繁殖，我们将分析角马尾毛生长过程中沉积的代谢物。我们将首先在已知身体状况的动物上校准我们的分析，然后用这种方法评估因不同原因死亡的动物的身体状况。这将使我们能够估计糟糕的身体状况如何降低角马的生存概率。使用类似的分析，我们将确定动物是否已经繁殖，并使用实地调查来测量小牛的存活率。为了理解人类的间接影响如何扩大到影响人口的恢复能力，我们将使用积分投影模型，这是一个框架，允许我们使用个人层面的数据来预测人口层面会发生什么。通过将经验数据收集与将个体生命率与人口动态联系起来的数学模型相结合，我们可以问，如果人类活动在特定地区增加，或者气候变化导致资源的不同分布，人口丰度会发生什么变化。这项研究将是人类对生态系统影响的最详细评估之一，并将为科学家和管理者提供关于如何在未来保持生态系统弹性的重要信息。

Globally, natural ecosystems are under threat due to the ever increasing pressures imposed by human activities. Many ecosystems are becoming fragmented or are being eroded at the edges while the effects of human disturbance are being felt even at the core of protected areas. Often, the impact of human activity or human-altered environments is obvious: when natural habitats are destroyed animals that can't escape will perish; humans directly harvest wild animals through poaching, hunting or fishing; infrastructure, such as wind turbines or roads, lead to collisions that kill animals; while diseases can spread from livestock and decimate wild populations. Beyond these direct impacts, much research has shown how humans can have more subtle effects on animals. For example, human activities can induce avoidance behaviour and restrict access to vital foraging areas, increase stress and vigilance levels, and interfere with sensory mechanisms by introducing noise and light into environments. While not as obvious, these indirect effects can have large impacts since many animals operate at the edge of their physiological limits whereby their energetic demands are finely balanced with resource availability, and weakened individuals can quickly succumb to predators, parasites, or disease. This means that even subtle impacts of human activity can significantly reduce the probability that an animal will survive and reproduce, which in turn can translate to large and sudden declines in the population.In this research we will investigate the effects of increased human pressures on the migratory population of wildebeest, a keystone species that inhabit the Greater Serengeti ecosystem in East Africa. We will assess how human disturbance is changing how animals move, how much time they spend consuming resources as opposed to being vigilant, and how these factors are affecting their body condition. We will test if these effects alter the survival probability of individuals and the chance that they have viable offspring.To evaluate the effects of human disturbance on movement and activities, we will use GPS devices and activity sensors mounted on collars that we will deploy on migratory wildebeest, combined with a comprehensive description of the distribution of resources (vegetation and soil nutrient maps) and risks (location of human infrastructure, tourism, illegal hunting activities, and natural predation). The GPS collars and sensors will allow us to track animals and determine how they respond to these environmental features, both in terms of how they move around in space, and how much time they allocate to different activities. To assess how body condition affects survival and reproduction we will analyse metabolites that get deposited in wildebeest tail hair as it grows. We will firstly calibrate our analysis on animals of known body condition, and then use this method to assess the body condition of animals that have died of different causes. This will allow us to estimate how poor body condition reduces a wildebeest's probability of survival. Using a similar analysis we will determine whether animals have reproduced and use field surveys to measure calf survival rates.To understand how indirect effects of humans scale-up to impact the resilience of the population, we will use Integral Projection Models, a framework that will allow us to use data at the individual level to predict what will happen at the population level. By combining empirical data collection with mathematical models that link individual vital rates with population dynamics, we can ask what happens to the population abundance if human activities increase in specific areas, or if climate change leads to different distributions of resources. This research will be one of the most detailed assessments of the effects of humans on an ecosystem and will provide scientists and managers with vital information about how to keep ecosystems resilient in the future.