A relative-motion method for parsing spatio-temporal behaviour of dyads using GPS relocation data

In this paper, we introduce a novel method for classifying and computing the frequencies of movement modes of intra- and interspecific dyads, focusing in particular on distance-mediated approach, retreat, following and side by side movement modes. Besides distance, other factors such as time of day, season, sex, or age can be included in the analysis to assess if they cause frequencies of movement modes to deviate from random. By subdividing the data according to selected factors, our method allows us to identify those responsible for (or correlated with) significant differences in the behaviour of dyadic pairs. We demonstrate and validate our method using both simulated and empirical data. Our simulated data were obtained from a relative-motion, biased random-walk (RM-BRW) model with attraction and repulsion components. Our empirical data were GPS relocation data collected from African elephants in Etosha National Park, Namibia. The simulated data were primarily used to validate our method while the empirical data were used to illustrate the types of behavioural assessment that our methodology reveals. Our method facilitates automated, observer-bias-free analysis of the locomotive interactions of dyads using GPS relocation data, which are becoming increasingly ubiquitous as telemetry and related technologies improve. It should open up a whole new vista of behavioural-interaction type analyses to movement and behavioural ecologists.本研究提出一种全新方法，用于对种内与种间二元个体对（dyads）的运动模式进行分类并计算其发生频率，重点关注由距离介导的趋近、撤离、跟随以及并排行进四类运动模式。除距离外，还可将日时段、季节、性别或年龄等其他因素纳入分析，以评估这些因素是否会导致运动模式的发生频率偏离随机水平。通过依据选定因素对数据进行细分，本方法可识别与二元个体对行为显著差异相关（或造成该差异）的因素。本研究通过模拟数据与实测数据两类样本，对所提方法进行了验证与演示。其中，模拟数据源自带有吸引与排斥组分的相对运动偏向随机游走（relative-motion biased random-walk, RM-BRW）模型；实测数据则取自纳米比亚埃托沙国家公园内非洲象的GPS重定位追踪数据（GPS relocation data）。模拟数据主要用于验证本方法的有效性，实测数据则用于展示本方法所能揭示的行为评估类型。随着遥感遥测及相关技术的不断迭代升级，GPS重定位追踪数据的应用愈发普及，本方法可借助此类数据实现二元个体对运动交互行为的自动化、无观察者偏倚分析。本方法将为运动生态学家与行为生态学家开辟行为交互类型分析的全新研究视野。