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.

人工照明对夜间光照水平（夜间人工光；ALAN）的修改是一种迅速增长的人类干扰形式，它影响着全球的自然环境。自然环境中的光线直接影响和间接影响着多种生理和生态过程，因此，光污染对物种、群落和生态系统的影响正逐渐显现出其重要性。小型猎物物种可能特别容易受到ALAN的影响，因为它使它们更加显眼，从而更容易受到视觉捕食者的捕食。理解如ALAN等干扰的影响对于濒危或受威胁物种尤为重要，因为这些影响有可能阻碍其恢复，但由于风险物种固有的低种群数量，干扰研究很少进行。濒危的斯蒂芬斯袋鼠鼠（SKR），Dipodomys stephensi，是一种受到城市扩张导致的栖息地破坏威胁的夜间啮齿动物。ALAN对其恢复的影响程度尚不清楚。在本研究中，我们考察了两种类型的ALAN（泛光和虫灯，分别以756和300流明计）在不同光照强度下以及满月和新月条件下对SKR觅食决策的影响。我们发现，与对照相比，ALAN降低了资源斑块耗竭的概率。此外，月相、光源距离和光类型相互作用，改变了SKR的觅食行为。在新月期间，SKR在控制条件下更有可能耗竭斑块，但随着与人工光源距离的增加，斑块耗竭的概率逐渐上升。满月期间，SKR的觅食活动和人工光源的影响减弱。我们的研究强调了ALAN降低了栖息地的适宜性，并提出了ALAN可能阻碍濒危夜间啮齿动物恢复的可能性。 主要结论：人工光源、月相和光源距离的相互作用对濒危袋鼠鼠的觅食能量产生负面影响，这对夜间猎物物种的管理和恢复具有重要意义。