Data from: Stigmergy, collective actions and animal social spacing

Collective animal behavior studies have led the way in developing models that account for a large number of individuals, but have mostly considered situations where alignment and attraction play a key role, such as in schooling and flocking.
By quantifying how animals react to each others' presence, when interaction is via conspecific avoidance rather than alignment or attraction, we present a mechanistic insight that enables us to link individual behavior and space use patterns. As animals respond to both current and past positions of their neighbors, the assumption that the relative location of individuals is statistically and history-independent is not tenable, underscoring the limitations of traditional space use studies. We move beyond that assumption, by constructing a framework to analyze spatial segregation of mobile animals when neighbor proximity may elicit a retreat, and by linking conspecific encounter rate to history-dependent avoidance behavior. Our approach rests on the knowledge that animals communicate by modifying the environment in which they live, providing a method to analyse social cohesion as stigmergy, a form of mediated animal-animal interaction. By considering a population of animals that mark the terrain as they move, we predict how the spatio-temporal patterns that emerge depend on the degree of stigmergy of the interaction processes. We find in particular that non-local decision rules may generate a nonmonotonic dependence of the animal encounter rate as a function of the tendency to retreat from locations recently visited by other conspecifics, which has fundamental implications to epidemic disease spread and animal sociality.

动物集体行为（Collective animal behavior）研究在构建适配大量个体的行为模型方面取得了开创性进展，但现有研究大多聚焦于同向对齐（alignment）与相互吸引（attraction）为核心驱动因素的场景，例如鱼类集群（schooling）与鸟类群聚（flocking）。本研究通过量化动物在同种个体避让（conspecific avoidance）而非同向对齐或相互吸引的交互模式下对同类存在的响应方式，提出了可关联个体行为与空间利用模式的机制性见解。由于动物会响应同类的当前与过往位置，“个体相对位置在统计上与历史无关”这一假设并不成立，这也凸显了传统空间利用研究的局限性。我们突破了该假设的局限，构建了一套分析框架：当同类邻近会触发动物避让行为时，可用于分析移动性动物的空间隔离；同时将同类遭遇率与依赖历史的避让行为相关联。本研究的核心前提是动物通过改造自身生存环境进行交流，据此我们提供了一种将社会凝聚力分析为痕量介导交互（stigmergy）的方法——这是一种间接介导的动物间交互形式。通过模拟在移动过程中标记地形的动物种群，我们可预测所涌现的时空模式如何随交互过程的痕量介导程度变化。我们尤其发现，非局部决策规则（non-local decision rules）可能导致动物遭遇率呈现出与“避让同类近期到访过的区域”倾向相关的非单调的依赖关系，这一发现对传染病传播与动物社会性行为研究均具有重要意义。