Stephens' kangaroo rat artificial light impacts on foraging data

Modification of nighttime light levels by artificial illumination (artificial light at night; ALAN) is a rapidly increasing form of human disturbance that affects natural environments worldwide. Light in natural environments influences a variety of physiological and ecological processes directly and indirectly and, as a result, the effects of light pollution on species, communities and ecosystems are emerging as significant. Small prey species may be particularly susceptible to ALAN as it makes them more conspicuous and thus more vulnerable to predation by visually oriented predators. Understanding the effects of disturbance like ALAN is especially important for threatened or endangered species as impacts have the potential to impede recovery, but due to low population numbers inherent to at-risk species, disturbance is rarely studied. The endangered Stephens’ kangaroo rat (SKR), Dipodomys stephensi, is a nocturnal rodent threatened by habitat destruction from urban expansion. The degree to which ALAN impacts their recovery is unknown. In this study, we examined the effects of ALAN on SKR foraging decisions across a gradient of light intensity for two types of ALAN, flood and bug lights (756 vs 300 lumen, respectfully) during full and new moon conditions. We found that ALAN decreased probability of resource patch depletion compared to controls. Moreover, lunar illumination, distance from the light source and light type interacted to alter SKR foraging. Under the new moon, SKR were consistently more likely to deplete patches under control conditions, but there was an increasing probability of patch depletion with distance from the source of artificial light. The full moon dampened SKR foraging activity and the effect of artificial lights. Our study underscores that ALAN reduces habitat suitability, and raises the possibility that ALAN may impede the recovery of at-risk nocturnal rodents. Main conclusion: Artificial light source, moon phase and distance to light interact to negatively impact foraging energetics of endangered kangaroo rats, which has implications for management and recovery of nocturnal prey species.夜间人工光（artificial light at night, ALAN）对夜间光照水平的改造，是一种在全球范围内快速加剧的人类干扰类型，正持续影响各地自然环境。自然环境中的光照会直接或间接调控多种生理与生态过程，因此光污染对物种、群落及生态系统的影响正逐渐受到广泛关注。小型猎物物种对ALAN尤其敏感：ALAN会提升其被视觉探测到的概率，进而使其更易成为视觉依赖型捕食者的捕猎目标。针对ALAN这类干扰的影响研究，对受威胁或濒危物种尤为关键——此类干扰可能阻碍其种群恢复，但由于濒危物种种群数量本就稀少，相关研究往往相对匮乏。 濒危物种斯蒂芬袋鼠鼠（Stephens’ kangaroo rat, SKR）的学名为*Dipodomys stephensi*，是一种夜行性啮齿动物，其生存受到城市扩张引发的栖息地破坏的严重威胁，目前尚不清楚ALAN对其种群恢复的影响程度。本研究设置光照强度梯度，针对泛光灯与灭虫灯两种ALAN类型（分别为756与300流明（lumen）），在满月与新月两种月相条件下，探究ALAN对SKR觅食决策的影响。 研究结果显示，相较于对照组，ALAN会降低觅食资源斑块被耗尽的概率。此外，月相光照、距光源距离以及光照类型三者的交互作用，会显著改变SKR的觅食行为：在新月条件下，SKR在对照组环境中耗尽觅食斑块的概率始终更高，但随着距人工光源距离的增加，其耗尽斑块的概率呈上升趋势；满月则会抑制SKR的觅食活动，同时削弱人工光的影响效应。 本研究证实，ALAN会降低栖息地适宜性，同时提示ALAN可能阻碍濒危夜行性啮齿动物的种群恢复。 主要结论：人工光源类型、月相以及距光源距离三者的交互作用，会对濒危袋鼠鼠的觅食能量学产生负面影响，该结果可为夜行性猎物物种的管理与种群恢复工作提供参考依据。