Insectivorous predators, including birds and bats, play crucial roles in trophic cascades. However, previous research on these cascades has often relied on permanent predator exclosures, which prevent the isolation of specific effects of birds and bats, given their different activity patterns throughout the day. Moreover, limited knowledge exists regarding the variations in individual effects of these predators under different biotic and abiotic conditions, such as changes in elevation. To address these uncertainties, our study aimed to investigate the distinct effects of bats and birds on arthropod densities in foliage and herbivory damage in lowland and highland rainforests of Papua New Guinea (PNG). Predator exclosures were established for one month to exclude diurnal or nocturnal predators across 120 saplings (ca. 2.5–4 m tall) selected from two lowland and two highland forests (i.e., 30 saplings per study site) along the Mt. Wilhelm transect in PNG. Arthropods were collected and measured, and herbivory damage was analyzed at the end of the experiment. Birds significantly reduced arthropod densities by 30%, particularly in arthropods longer than 10 mm, regardless of elevation. Additionally, both birds and bats appeared to mitigate herbivory damage in highland forests, with protected saplings displaying up to 189% more herbivory. Our results support previous studies that have demonstrated the ability of insectivorous predators to reduce leaf damage through the control of arthropods. Furthermore, our approach highlights the importance and necessity of further research on the role of seasons and elevations in trophic cascades.

中文翻译：

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鸟类和蝙蝠减少了巴布亚新几内亚高原森林的食草破坏


食虫捕食者，包括鸟类和蝙蝠，在营养级联中起着至关重要的作用。然而，以前对这些级联的研究通常依赖于永久性捕食者封闭，鉴于鸟类和蝙蝠全天的活动模式不同，这可以防止隔离它们的特定影响。此外，关于这些捕食者在不同生物和非生物条件下的个体影响变化（例如海拔变化）的知识有限。为了解决这些不确定性，我们的研究旨在调查蝙蝠和鸟类对巴布亚新几内亚 （PNG） 低地和高地热带雨林树叶节肢动物密度和食草动物损害的不同影响。从巴布亚新几内亚威廉山横断面的两个低地和两个高地森林（即每个研究地点 30 棵树苗）中选择的 120 棵树苗（约 2.5-4 m 高）中，建立了为期一个月的捕食者围栏，以排除昼夜或夜间捕食者。收集并测量节肢动物，并在实验结束时分析食草性损伤。鸟类将节肢动物密度显著降低了 30%，尤其是在长度超过 10 毫米的节肢动物中，无论海拔高度如何。此外，鸟类和蝙蝠似乎都能减轻高原森林中的食草危害，受保护的树苗的食草性增加了 189%。我们的结果支持以前的研究，这些研究已经证明食虫捕食者能够通过控制节肢动物来减少叶子损伤。此外，我们的方法强调了进一步研究季节和高程在营养级联中的作用的重要性和必要性。