Department of Mathematics, University of Florida, Gainesville, FL, USA.
Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, GA, USA.
J R Soc Interface. 2017 Oct;14(135). doi: 10.1098/rsif.2017.0555.
Animals share a variety of common resources, which can be a major driver of conspecific encounter rates. In this work, we implement a spatially explicit mathematical model for resource visitation behaviour in order to examine how changes in resource availability can influence the rate of encounters among consumers. Using simulations and asymptotic analysis, we demonstrate that, under a reasonable set of assumptions, the relationship between resource availability and consumer conspecific encounters is not monotonic. We characterize how the maximum encounter rate and associated critical resource density depend on system parameters like consumer density and the maximum distance from which consumers can detect and respond to resources. The assumptions underlying our theoretical model and analysis are motivated by observations of large aggregations of black-backed jackals at carcasses generated by seasonal outbreaks of anthrax among herbivores in Etosha National Park, Namibia. As non-obligate scavengers, black-backed jackals use carcasses as a supplemental food resource when they are available. While jackals do not appear to acquire disease from ingesting anthrax carcasses, changes in their movement patterns in response to changes in carcass abundance do alter jackals' conspecific encounter rate in ways that may affect the transmission dynamics of other diseases, such as rabies. Our theoretical results provide a method to quantify and analyse the hypothesis that the outbreak of a fatal disease among herbivores can potentially facilitate outbreaks of an entirely different disease among jackals. By analysing carcass visitation data, we find support for our model's prediction that the number of conspecific encounters at resource sites decreases with additional increases in resource availability. Whether or not this site-dependent effect translates to an overall decrease in encounters depends, unexpectedly, on the relationship between the maximum distance of detection and the resource density.
动物共享各种共同资源，这可能是同种相遇率的主要驱动因素。在这项工作中，我们实现了一种空间显式的资源访问行为数学模型，以研究资源可利用性的变化如何影响消费者之间的相遇率。通过模拟和渐近分析，我们证明，在一组合理的假设下，资源可利用性和消费者同种相遇之间的关系不是单调的。我们描述了最大相遇率和相关的临界资源密度如何取决于系统参数，如消费者密度和消费者可以检测和响应资源的最大距离。我们理论模型和分析的假设是由纳米比亚埃托沙国家公园食草动物季节性炭疽爆发产生的尸体周围大量聚集的黑背豺狼观察结果所驱动的。作为非专性食腐动物，黑背豺狼在有尸体时会将其作为补充食物资源利用。虽然豺狼从摄入炭疽尸体中似乎不会感染疾病，但它们对尸体丰度变化的运动模式的改变确实会以可能影响其他疾病（如狂犬病）传播动态的方式改变豺狼的同种相遇率。我们的理论结果提供了一种量化和分析假设的方法，即食草动物致命疾病的爆发可能会促进豺狼中完全不同疾病的爆发。通过分析尸体访问数据，我们发现支持我们模型的预测，即在资源点上同种相遇的数量随着资源可用性的额外增加而减少。这种基于地点的效应是否会转化为相遇次数的总体减少，出乎意料地取决于检测的最大距离和资源密度之间的关系。
