Supplementary Data: Camera trapping and GPS telemetry for detecting and quantifying animal interactions: Not anything goes

Abstract GPS telemetry and camera trapping are two widely used approaches to detect animal interactions involving wildlife. However, while the former follows an individual-based approach, the latter follows a population-based approach, which may lead to different outcomes when describing interaction networks. This study compares GPS telemetry, regular grid camera trapping (CT-RG), and resource monitoring through camera trapping (e.g., in water or food; CT-RM) for detecting and quantifying animal interactions. We used simulated trajectories of 150 individuals of 3 imaginary species. We simulated 9 different scenarios of resource visitation frequency and spatial resource aggregation to assess the potential influence of animal behavior and landscape structure. The simulated trajectories were sampled using the three approaches with six different sampling efforts each, and the direct and indirect interactions between the three species were quantified. Additionally, CT-RG and CT-RM were applied in Doñana National Park to evaluate their differences and limitations in field application. In terms of simulation, CT-RM offered the best performance in detecting direct interactions, and GPS achieved good performance at high efforts. Both also achieved good performance in detecting indirect interactions. CT-RG, on the other hand, missed most direct and indirect interactions, but correctly identified all pairs of species interacting indirectly. In the field trial, CT-RM and CT-RG detected almost the same number of pairs interacting indirectly. However, CT-RG missed at least half of the pairs of species interacting directly. GPS performs better than CT-RM when the resource is spatially aggregated, but the opposite is true when the resource is frequently visited. To summarize, CT-MR is the most reliable method for detecting interactions when resource monitoring is feasible (e.g., small ponds in arid areas). Otherwise, GPS may show better performance, although it may miss direct interactions. CT-RG should only be used to detect potential indirect interactions between species, not to quantify them.摘要 GPS遥测（GPS telemetry）与相机诱捕监测（camera trapping）是当前探测野生动物相关动物相互作用的两种常用方法。然而，二者的研究范式存在本质差异：前者采用基于个体的方法，后者采用基于种群的方法，这会导致在描述物种相互作用网络时得到不同的结果。本研究针对探测与量化动物相互作用这一目标，对比了GPS遥测、规则网格相机诱捕监测（CT-RG）以及基于相机诱捕的资源监测（如针对水源或食物的监测；CT-RM）三种方法。本研究以3种假想物种的150个个体的模拟运动轨迹为研究对象，设置了9种不同的资源访问频率与空间聚集程度情景，以评估动物行为与景观结构对相互作用探测的潜在影响。针对三种研究方法，我们分别设置6种不同的采样强度对模拟轨迹进行采样，并量化了3个物种种群间的直接与间接相互作用。此外，我们在多尼亚纳国家公园开展了实地应用试验，以评估CT-RG与CT-RM在野外应用中的差异与局限性。模拟试验结果表明，CT-RM在探测直接相互作用方面表现最优，而GPS遥测在高采样强度下也能取得良好的探测效果；二者在探测间接相互作用时同样表现优异。反观CT-RG，其虽能准确识别所有存在间接相互作用的物种种对，但会遗漏绝大多数直接与间接相互作用。实地试验中，CT-RM与CT-RG探测到的间接相互作用物种种对数量几乎一致，但CT-RG会遗漏至少半数的直接相互作用物种种对。当资源呈空间聚集分布时，GPS遥测的表现优于CT-RM；而当资源被频繁访问时，情况则恰好相反。综上，当资源监测具备可行性时（如干旱地区的小型水塘），CT-RM是探测动物相互作用的最可靠方法；反之，GPS遥测则可能表现更优，不过其仍可能遗漏部分直接相互作用。CT-RG仅可用于探测物种间潜在的间接相互作用，无法用于量化这类相互作用。