Data from: Nonlinear scaling of foraging contacts with rodent population density

Density-dependent shifts in population processes like territoriality, reproduction, dispersal, and parasite transmission are driven by changes in contacts between individuals. Despite this, surprisingly little is known about how contacts change with density, and thus the mechanisms driving density-dependent processes. A simple linear contact-density function is often assumed, but this is not based on a sound basis of empirical data. We addressed this question using a replicated, semi-natural experiment in which we measured contacts at feeding stations between multimammate mice, Mastomys natalensis, across ten distinct, linearly increasing densities between 10 and 272 animals/ha. Unexpectedly, unique contacts increased not linearly but sigmoidally with density, which we attribute to the species’ scramble competition mating system, small-scale dominance/avoidance and absence of territoriality. These results provide new insights into how species’ characteristics can relate to density-dependent changes in contacts, and the unexpected shape of the contact-density function warrants that density-dependence in ecological models, such as parasite transmission models, must be parameterized with care.

种群过程（如领域行为、繁殖、扩散及寄生虫传播）的密度依赖型变化，均由个体间接触模式的改变所驱动。尽管如此，学界对接触模式随种群密度的变化规律仍知之甚少，因此对驱动密度依赖型过程的具体机制也缺乏深入认知。现有研究通常假设存在简单的线性接触-密度函数，但该假设并未获得可靠的经验数据支撑。本研究通过一项重复开展的半自然实验解答了上述问题：实验以多乳头小鼠（Mastomys natalensis）为研究对象，在投喂站记录其个体间的接触行为，并设置了10个从10至272只/公顷逐级线性递增的种群密度梯度。出乎意料的是，独特接触次数并未随种群密度呈线性增长，而是呈现出S形（sigmoidal）变化趋势。我们将该现象归因于该物种的掠夺式（scramble）竞争交配体系、小规模的优势避让行为以及缺乏领域行为。本研究结果为物种特性与接触行为的密度依赖型变化之间的关联提供了全新视角；同时，接触-密度函数的非预期形态也提示，在寄生虫传播模型等生态学模型中，对密度依赖关系的参数化过程必须格外谨慎。