Data from: Insectivorous birds and bats outperform ants in the top-down regulation of arthropods across strata of a Japanese temperate forest

Birds, bats, and ants are recognized as significant arthropod predators. However, empirical studies reveal inconsistent trends in their relative roles in top-down control across strata. Here, we describe the differences between forest strata in the separate effects of birds, bats, and ants on arthropod densities and their cascading effects on plant damage. We implemented a factorial design to exclude vertebrates and ants in both the canopy and understory. Additionally, we separately excluded birds and bats from the understory using diurnal and nocturnal exclosures. At the end of the experiments, we collected all arthropods and assessed herbivory damage. Arthropods responded similarly to predator exclusion across forest strata, with a density increase of 81% on trees without vertebrates and 53% without both vertebrates and ants. Additionally, bird exclusion alone led to an 89% increase in arthropod density, while bat exclusion resulted in a 63% increase. Herbivory increased by 42% when vertebrates were excluded and by 35% when both vertebrates and ants were excluded. Bird exclusion alone increased herbivory damage by 28%, while the exclusion of bats showed a detectable but non-significant increase (by 22%). In contrast, ant exclusion had no significant effect on arthropod density or herbivory damage across strata. Our results reveal that the effects of birds and bats on arthropod density and herbivory damage are similar between the forest canopy and understory in this temperate forest. In addition, ants were not found to be significant predators in our system. Furthermore, birds, bats, and ants appeared to exhibit antagonistic relationships in influencing arthropod density. These findings highlight, unprecedentedly, the equal importance of birds and bats in maintaining ecological balance across different strata of a temperate forest.

鸟类、蝙蝠与蚂蚁均被视为节肢动物（arthropod）的重要捕食者。然而现有实证研究表明，不同森林层位中三者在下行调控（top-down control）中的相对作用呈现出不一致的趋势。本研究旨在阐明不同森林层位中，鸟类、蝙蝠及蚂蚁各自对节肢动物密度的影响，以及其对植物受害程度的级联效应（cascading effects）差异。本研究采用析因实验设计（factorial design），在林冠层（canopy）与林下层（understory）中分别开展脊椎动物与蚂蚁的排除实验；此外，针对林下层，我们通过日间与夜间排除笼分别实现鸟类与蝙蝠的排除处理。实验结束后，我们采集所有节肢动物样本并评估植食性损伤（herbivory damage）程度。
不同森林层位的节肢动物对捕食者排除的响应模式相似：脊椎动物排除组的节肢动物密度提升81%，同时排除脊椎动物与蚂蚁的处理组密度提升53%。此外，仅排除鸟类的处理组节肢动物密度增加89%，仅排除蝙蝠的处理组则增加63%。植食性损伤程度在脊椎动物排除组中提升42%，同时排除脊椎动物与蚂蚁的处理组提升35%。仅排除鸟类的处理组植食损伤增加28%，仅排除蝙蝠的处理组虽有可观测到的提升（22%）但未达到显著性水平。相较而言，蚂蚁排除处理在所有森林层位中均未对节肢动物密度或植食性损伤产生显著影响。
本研究结果表明，在该温带森林中，鸟类与蝙蝠对节肢动物密度及植食性损伤的调控效应在林冠层与林下层之间并无显著差异；此外，本实验体系中蚂蚁并未表现出显著的捕食者作用。进一步分析显示，鸟类、蝙蝠与蚂蚁在调控节肢动物密度时呈现出拮抗关系。本研究首次揭示，鸟类与蝙蝠在维持温带森林不同层位生态平衡方面具有同等重要的作用。