Illuminating prey selection in an insectivorous bat community, exposed to artificial light at night

1.Light pollution has been increasing around the globe and threatens to disturb natural rhythms of wildlife species. Artificial light impacts the behaviour of insectivorous bats in numerous ways, including foraging behaviour, which may in turn lead to altered prey selection.

2.In a manipulative field experiment, we collected faecal samples from six species of insectivorous bats in naturally dark and artificially lit conditions, and identified prey items using molecular methods to investigate effects of light pollution on prey selection.

3.Proportional differences of identified prey were not consistent and appeared to be species specific. Red bats, little brown bats, and gray bats exhibited expected increases in moths at lit sites. Beetle-specialist big brown bats had a sizeable increase in beetle consumption around lights, while tri-colored bats and evening bats showed little change in moth consumption between experimental conditions. Dietary overlap was high between experimental conditions within each species, and dietary breadth only changed significantly between experimental conditions in one species, the little brown bat.

4.Policy implications. Our results, building on others, demonstrate that bat-insect interactions may be more nuanced than the common assertion that moth consumption increases around lights. They highlight the need for a greater mechanistic understanding of bat-light interactions to predict which species will be most affected by light pollution. Given differences in bat and insect communities, we advocate biologists, land stewards, and civil planners work collaboratively to determine lighting solutions that minimize changes in foraging behaviour of species in the local bat community. Such efforts may allow stakeholders to more effectively craft management strategies to minimize unnatural shifts in prey selection caused by artificial lights.

1. 全球范围内光污染问题日益加剧，正持续威胁野生动物种群的自然节律。人工光源会通过多种途径影响食虫蝙蝠（insectivorous bats）的行为，其中包括觅食行为（foraging behaviour），进而可能改变其猎物选择偏好。
2. 本研究通过控制性野外实验（manipulative field experiment），在自然黑暗与人工光照两种环境下采集了6种食虫蝙蝠的粪便样本，并利用分子生物学方法（molecular methods）鉴定猎物种类，以此探究光污染对蝙蝠猎物选择的影响。
3. 经鉴定的猎物比例差异并不统一，且呈现出物种特异性。红蝙蝠、小棕蝠与灰蝙蝠在光照环境下的蛾类捕食量均出现了预期的提升。以甲虫为专性猎物的大棕蝠，其周边有光源时的甲虫捕食量大幅增加；而三色蝙蝠与夜蝠在两种实验环境下的蛾类捕食量则几乎无变化。各物种在两种实验条件下的饮食生态位重叠（dietary overlap）度均较高，且仅小棕蝠的食性广度（dietary breadth）在两种实验条件间发生了显著变化。
4. 政策启示
本研究结果结合已有同类研究表明，蝙蝠-昆虫互作（bat-insect interactions）或许比“光照环境下蛾类捕食量增加”这一普遍论断更为复杂精细。研究凸显了深入理解蝙蝠与光照互作机制的必要性，以此预测哪些物种最易受光污染影响。鉴于蝙蝠与昆虫群落存在物种差异，我们呼吁生物学家、土地管理者与城市规划者协同合作，制定可最大程度降低本地蝙蝠群落物种觅食行为改变的光照方案。此类举措可帮助利益相关方更有效地制定管理策略，以减少人工光源引发的猎物选择非自然偏移。