Focal vs. faecal: Seasonal variation in the diet of wild vervet monkeys from observational and DNA metabarcoding data

1. Assessing the diet of wild animals reveals valuable information about their ecology and trophic relationships that may help elucidate dynamic interactions in ecosystems and forecast responses to environmental changes. 2. Advances in molecular biology provide valuable research tools in this field. However, comparative empirical research is still required to highlight strengths and potential biases of different approaches. Therefore, this study compares environmental DNA and observational methods for the same study population and sampling duration. 3. We employed DNA metabarcoding assays targeting plant and arthropod diet items in 823 faecal samples collected over 12 months in a wild population of an omnivorous primate, the vervet monkey (Chlorocebus pygerythrus). DNA metabarcoding data were subsequently compared to direct observations. 4. We observed the same seasonal patterns of plant consumption with both methods, however, DNA metabarcoding showed considerably greater taxonomic coverage and resolution compared to observations, mostly due to the construction of a local plant DNA database. We found a strong effect of season on variation in plant consumption largely shaped by the dry and wet seasons. The seasonal effect on arthropod consumption was weaker but feeding on arthropods was more frequent in spring and summer, showing overall that vervets adapt their diet according to available resources. The DNA metabarcoding assay outperformed also direct observations of arthropod consumption in both taxonomic coverage and resolution. 5. Combining traditional techniques and DNA metabarcoding data can therefore not only provide enhanced assessments of complex diets or reveal trophic interactions to the benefit of wildlife conservationists and managers but also opens new perspectives for behavioural ecologists studying whether diet variation in social species is induced by environmental differences or might reflect selective foraging behaviours.

1. 评估野生动物的饮食构成，可揭示其生态学特征与营养级关系相关的宝贵信息，有助于阐明生态系统中的动态相互作用，并预测其对环境变化的响应。2. 分子生物学的进展为该领域提供了极具价值的研究工具。然而，当前仍需开展对比性实证研究，以明确不同研究方法的优势与潜在偏倚。因此，本研究针对同一研究种群与采样周期，对比了环境DNA（environmental DNA）与观测法两种研究手段。3. 本研究针对一个杂食性灵长类动物——黑长尾猴（Chlorocebus pygerythrus）的野生种群，收集了为期12个月的823份粪便样本，并针对其饮食中的植物与节肢动物类群，开展了DNA宏条形码（DNA metabarcoding）检测。随后，将DNA宏条形码检测数据与直接观测结果进行了对比。4. 两种方法均观测到了植物取食的相同季节模式，但DNA宏条形码检测的分类覆盖度与分辨率均显著优于观测法，这主要得益于本地植物DNA数据库的构建。研究发现，季节对植物取食变异存在显著影响，这种变异主要受干湿季驱动。而季节对节肢动物取食的影响相对较弱，但黑长尾猴在春夏季取食节肢动物的频率更高，整体表明黑长尾猴会根据可获取的资源调整其饮食结构。此外，在分类覆盖度与分辨率两方面，DNA宏条形码检测同样优于节肢动物取食的直接观测结果。5. 因此，将传统研究技术与DNA宏条形码数据相结合，不仅能够提升复杂饮食构成的评估精度、揭示营养级相互作用，从而为野生动物保护者与管理者提供助力，同时也为行为生态学家开辟了全新的研究视角——可用于探究群居物种的饮食变异究竟是由环境差异诱导产生，还是反映了选择性觅食行为。