Trophic interactions of two aquatic anurans from the mid-elevation evergreen forests of the Western Ghats, India

Food is an important resource that is often partitioned among co-occurring species. Anurans (Frogs and Toads) are a diverse group of vertebrates distributed globally and are known to be generalist predators. While the dietary ecology of anurans has been extensively studied in the Neotropics, our knowledge from parts of South and SE Asia is limited. Here, we study the dietary ecology of two anurans, belonging to ancient families (Micrixalidae and Nyctibatrachidae) from a riverine ecosystem of the wet-evergreen forests of the Western Ghats, India. We quantified both the quantity and composition of diet by flushing the stomachs of anurans. The quantity of prey items consumed by the two species as well as sexes was scaled with body size. The composition, as well as dietary niche, were significantly different between the two species. Despite the diet composition being different, their diets overlapped partially but the overlap was significantly greater than expected. Finally, we found the diet composition of the two species to be correlated with morphological characteristics of the head shape and activity period. Overall, our findings suggest that the two species partition resources along temporal, microhabitat, and morphological axes and appear to be generalist, sit-and-wait foragers. Our findings underscore the need for future research on dietary ecology in the fast-changing landscapes of the Western Ghats as well as other parts of Asia.

食物是一类关键资源，常被同域共存的物种分化利用。无尾两栖类（Anurans，即蛙与蟾蜍）是一类全球分布、物种多样性丰富的脊椎动物类群，被公认为广食性捕食者。尽管学界已对新热带区的无尾两栖类食性生态开展了大量研究，但南亚与东南亚部分区域的相关研究仍较为匮乏。本研究以印度西高止山脉湿润常绿林河流生态系统中的两种无尾两栖类为研究对象，它们分别隶属于古老的扁手蛙科（Micrixalidae）与夜蛙科（Nyctibatrachidae）。我们通过胃灌洗法采集无尾两栖类的胃容物，量化了两种蛙类的食物摄入量与食性组成。两种蛙类及其不同性别的猎物摄取量均随个体体型发生缩放。二者的食性组成与生态位均存在显著差异。尽管二者食性组成存在差异，但它们的食谱仍存在部分重叠，且该重叠度显著高于随机预期水平。此外，我们发现两种蛙类的食性组成与其头部形态特征以及活动节律均存在相关性。综合来看，本研究结果表明，两种蛙类通过时间、微生境与形态维度实现资源分化，且均属于广食性的静候型捕食者。本研究结果凸显了在西高止山脉及亚洲其他区域快速变化的景观中开展无尾两栖类食性生态研究的必要性。