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

Abstract

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. 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. Proportional differences in identified prey were not consistent and appeared to be species specific. Red bats, little brown bats and grey 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‐coloured 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. 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.

Assessing the effects of artificial light at night on biodiversity across latitude – Current knowledge gaps

“…Data were binned in 5° categories. (Cravens et al, 2017;Dwyer et al, 2013). Seas and large lakes have been excluded.…”

No effect of artificial light of different colors on commuting Daubenton's bats (Myotis daubentonii) in a choice experiment

“…Bats are strongly affected by light at night, and the indirect attraction of bats by accumulated insects around illumination has been known for a long time (Rydell, ; Rydell & Racey, ). This effect has more recently been shown in experimental setups (Cravens, Brown, Divoll, & Boyles, ; Minnaar, Boyles, Minnaar, Sole, & McKechnie, ; Spoelstra et al., ; Wakefield, Stone, Jones, & Harris, ). However, slow‐flying bats, such as Myotis and Plecotus species, generally avoid illumination (Furlonger, Dewar, & Fenton, ; Rydell, ; Spoelstra et al., ).…”

DNA metabarcoding in diet studies: Unveiling ecological aspects in aquatic and terrestrial ecosystems

“…Yet, the diet of several species was investigated more than twice (Table S1). For instance, after an initial description of the dietary habits of the little brown bat Myotis lucifugus based on metabarcoding approaches (Clare et al, ; Clare et al, ), this species was used in comparative dietary studies assessing human influence on feeding habits of bats (Cravens et al, ) and to improve the identification of arthropods in DNA‐based diet studies (Jusino et al, ). Favoring their place as good biological models in the assessment of vertebrates' diets, bat species have distinct feeding and foraging habits, and different ecologic requirements and are widely distributed across a variety of terrestrial ecosystems, even in human‐altered habitats (Kemp et al, ; Long, Kurta, & Clemans, ).…”

“…However, generally, these studies are mostly descriptive, and only about one third (47 out 150) addressed impacts of human‐mediated changes in diets (37% of the studies on terrestrial organisms and 22% of the studies on aquatic taxa, see Table S1). For terrestrial species, most of these studies focused on the impacts of urbanized areas (Bohmann et al, ; Coghlan et al, ; Cravens et al, ; Forin‐Wiart et al, ; Groom et al, ; Khanam, Howitt, Mushtaq, & Russell, ; Lim, Ramli, Bhassu, & Wilson, ; Quéméré et al, ; Smith, Thomas, Levi, Wang, & Wilmers, ; Sullins et al, ) and landscape changes due to agriculture (e.g., Branco et al, ; Clare et al, , ; Sugimoto et al, ) in trophic interactions. Importantly, the results obtained so far provide substantial knowledge toward effective conservation planning and management, by identifying the impacts of introduced species, both revealing competition with native fauna (Brown et al, ; Egeter, Bishop, & Robertson, ; Robeson II et al, ; Zarzoso‐Lacoste et al, ) and uncovering the importance of introduced plant species to the diet of endangered species (Ando et al, ).…”

“…There have also been some studies focusing on the diets of reintroduced or recovering populations (Kowalczyk et al, ; Pansu et al, ; Pinho et al, ) and on the effects of hunting in niche partitioning between both herbivores (Pansu et al, ) and carnivores (Smith et al, ). Additionally, the effects of pollution have been addressed twice, with light pollution having species‐specific effects on bats' feeding habits (Cravens et al, ) and trace metal pollution modulating food preferences of the wood mouse Apodemus sylvaticus (Ozaki et al, ). So far, and to the best of our knowledge and based on our compilation, only one study focused on the effects of climate change on bats trophic niche, uncovering a profound impact on trophic webs (de Oliveira, ).…”