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Activity levels of five bat species at Great Hollow Nature Preserve, New Fairfield, Connecticut, USA, 2016 and 2017 (combined across the three lighting treatments). Boxes show the median and 25th to 75th percentiles, and whiskers represent minimum and maximum values
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Artificial light at night (ALAN) is a rapidly intensifying form of environmental degradation that can impact wildlife by altering light‐mediated physiological processes that control a broad range of behaviors. Although nocturnal animals are most vulnerable, ALAN's effects on North American bats have been surprisingly understudied. Most of what is k...
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Artificial light at night (ALAN) is a global pollutant that disrupts circadian rhythmicity and a broad range of physiological processes and behaviors in animals. However, ALAN sensitivity can vary greatly even among closely related species and urgently needs study for much of the world's nocturnal wildlife, including bats. While an increasing numbe...
Citations
... Two separate field experiments artificially lit naturally dark areas, and both found that big brown and little brown bats avoided lit sites (Seewagen and Adams 2021; Cravens and Boyles 2019). In addition, one of the studies also found the silver-haired bat to avoid lit sites (Seewagen and Adams 2021). No effect of ALAN was found on the eastern red bat, hoary bat, evening bat, or tricolored bat in these studies (Seewagen and Adams 2021; Cravens and Boyles 2019). ...
Background
The timing of behavior and habitat use of nocturnal animals can be influenced by the lunar cycle in nature. The prevalence of artificial light at night (ALAN) has been recognized as a source of environmental pollution. The interaction between ALAN and the lunar cycle on bat behavior is important for understanding anthropogenic effects on bats. We utilized a decade (2012–2022) of acoustic monitoring data collected in North Carolina, United States, to investigate the relationship between bat activity, lunar cycle, and light pollution. We examined whether the amount of lunar illumination affected species-specific nightly activity and whether hourly bat activity patterns varied between nights with different moon phases. We further investigated if the relationship between bat activity and the lunar cycle might be altered by light pollution.
Results
We found that seven bat species showed activity variation across nights in relation to the amount of moon illumination when ALAN was absent. In general, bats were less active on full moon nights compared to new moon nights. Light pollution interacted with the bat–lunar relationship in five of the seven species, masking the effect of the lunar cycle. We identified delayed bat activity patterns on nights with a full or waxing moon in seven species, and light pollution altered that pattern in four species. Overall, ALAN was associated with decreased bat activity independent of lunar cycle effects.
Conclusions
Our study demonstrated that at a broad spatial scale, ALAN negatively affected many North American temperate bat species and altered their lunar chronobiology. As light pollution is spreading to historically dark areas and habitats, ALAN might couple with other threats, such as the white-nose syndrome or climate change, to cause cascading damage in the environment that depends on ecosystem services such as pest control provided by bats. We argue that further research and conservation actions are needed to mitigate the impact of light pollution.
... Furthermore, mating likely coincides with migration (Glass, 1966;Stuewer, 1948), and eastern red bats have been observed migrating during the day (Barbour & Davis, 1969;Hatch et al., 2013). Eastern red bats also roost in well-lit conditions (i.e., in tree canopies), can emerge to forage before sunset (Beilke et al., 2023), exhibit peaks in activity at dawn and dusk (Beilke et al., 2021), and do not avoid moonlight (Arndt, 2018) or artificial light at night (Seewagen & Adams, 2021). Thus, mating events may frequently occur while there is enough ambient light for bats to discern fur color. ...
Sex differences in body color (i.e., sexual dichromatism) are rare in bats and, more broadly, in mammals. The eastern red bat ( Lasiurus borealis ) is a common tree‐roosting bat that occupies much of North America and has long been described as sexually dichromatic. However, previous research on this species found that absolute body size and collection year were better predictors of fur color in preserved specimens than sex. We revisited this issue and photographed 82 live eastern red bats under standardized conditions, then used image analysis to quantify pelage hue, saturation, and value. We used an information theoretic approach to evaluate four competing hypotheses about the principal drivers of color differences in the fur of eastern red bats. Our analyses demonstrated that sex was a better predictor of pelage color than body size; males had redder, more saturated, and lighter pelages than females. Additionally, the fur color of juvenile versus adult bats differed somewhat, as juveniles were darker than adults. In general, absolute body size (i.e., forearm length in bats) was a poor predictor of color in live eastern red bats. In an exploratory post‐hoc analysis, we confirm that fur color is related to body mass (i.e., a proxy for body condition in bats), suggesting color might serve as a sexually selected signal of mate quality in this partially diurnal species. Future work should investigate the functional role of sexual dichromatism in this species, which could be related to signaling or possibly thermoregulation.
... Artificial light at night (ALAN) corresponds to a change in the natural levels of nighttime lighting as a result of human activities that generate light (Falchi et al., 2016). ALAN is among the artificial environmental conditions that most affect wildlife in urban areas and is often described as photopollution (e.g., Russ et al., 2017;Owens et al., 2020;Seewagen and Adams, 2021). ...
This study investigated the potential influence of artificial nocturnal lighting (ALAN) on the diet and behavior of the owl Tyto furcata in the Caatinga biome, northeastern Brazil, from 2016 to 2021. The diet of T. furcata was compared between two adjacent areas, the National Park (PARNA) Furna Feia and the urban area of the municipality of Mossoró, a semiarid region of the west of the State of Rio Grande do Norte, with different ALAN intensities. The analysis of the geographic information system (GIS), using night images from the SNPP and NOAA-20 satellites, identified that ALAN in PARNA Furna Feia was absence, while in the urban perimeter of Mossoró, ALAN was present. The diet of T. furcata owls at PARNA Furna Feia comprised mostly of bats and nocturnal rodents captured at night under rocks and caves. In the urban area of Mossoró, the diet consisted mainly of diurnal birds and rodents captured during the night, when they rested in roosts under ALAN. Thus, urbanization affects the foraging behavior and diet of this bird of prey in Caatinga. ALAN appears to be one of the environmental conditions that T. furcata favors in urban habitats in the Caatinga biome, as it allows nightly hunting under artificial lighting of birds aggregated in roosts.
... Light pollution has mixed effects on bat communities and can simultaneously have negative effects on bats by reducing insect populations or disrupting foraging activity (Stone et al., 2015) but can also provide enhanced feeding opportunities for some insectivorous bat species that feed effectively at artificial lights that attract moths and other phototactic insects (Voigt et al., 2021;Barré et al., 2022;Frick et al., 2023). Responses of bat species to Artificial Light at Night (ALAN) vary with foraging behavior and landscape context but could influence bat community composition and habitat use at broad scales (Cravens et al., 2018;Seewagen and Adams, 2021;Barré et al., 2022). ...
... Reducing or avoiding use of pesticides is recommended as best-practice for supporting local insect abundance and diversity (Frampton and Dorne, 2007). Additionally, reducing certain types of artificial light in and near gardens or garden features could reduce disturbance to some bats (Mathews et al., 2015;Seewagen and Adams, 2021). In larger gardens, features such as adding a pond or other water feature could provide drinking water for bats and may be particularly beneficial in arid climates with limited water availability. ...
... Two separate eld experiments arti cially lit naturally dark areas, and both found that big brown and little brown bats avoided lit sites (Seewagen, Adams, 2021, Cravens, Boyles, 2019). Additionally, one of the studies also found the silverhaired bat to avoid lit sites (Seewagen, Adams, 2021). No effect of ALAN was found on the eastern red bat, hoary bat, evening bat, or tricolored bat in these studies (Seewagen, Adams, 2021, Cravens, Boyles, 2019). ...
Background
The timing of behavior and habitat associations of nocturnal animals can be influenced by the lunar cycle in nature. The prevalence of artificial light at night (ALAN) has been recognized as a source of environmental pollution. The interaction between ALAN pollution and the lunar cycle on bat behavior is important for understanding anthropogenic effects on bats. We utilized a decade (2012–2022) of acoustic monitoring data collected in North Carolina, United States, to investigate the relationship between bat activity, lunar cycle, and ALAN pollution in temperate insectivorous bats. We examined whether the amount of lunar illumination affected species-specific nightly activity and whether hourly bat activity patterns varied between nights with different moon phases. We further investigated if the relationship between bat activity and the lunar cycle might be altered by ALAN pollution.
Results
We found that seven bat species showed activity variation across nights in relation to the amount of moon illumination when ALAN pollution was absent. Generally, bats were less active on full moon nights compared to new moon nights. ALAN pollution interacted with the bat-lunar relationship in five of the seven species, masking the effect of the lunar cycle. We identified delayed bat activity patterns on nights with a full or waxing moon in seven species, and ALAN pollution altered that pattern in four species. Overall, ALAN pollution was associated with decreased bat activity independent of lunar cycle effects.
Conclusions
Our study demonstrated that at a broad spatial scale, ALAN pollution negatively affected many North American temperate bat species and altered their lunar chronobiology. As the cost of illumination declines and the economic benefits of nighttime farming and other activities increase, ALAN pollution is spreading to historically dark areas and habitats. ALAN pollution might couple with other threats, such as the white-nose syndrome or climate change, to cause cascading damage in the environment that depends on ecosystem services provided by bats. We argue that further research and conservation actions are needed to mitigate the impact of ALAN pollution.
... The effects of ALAN on bats are often highly species-specific, however, with some species avoidant of lights and others attracted to them by associated concentrations of insect prey (Stone et al., 2015;Rowse et al., 2016). This attraction-repulsion dynamic and the barrier ALAN poses to some species' space-use but not others can be strong enough to alter bat community composition at local to landscape scales (Azam et al., 2016;Schoeman, 2016;Seewagen and Adams, 2021). ...
... This knowledge gap is an impediment to the protection of bats in land-use planning and policy (Pauwels et al., 2019;Schroer et al., 2020). To help address this information need for North America, we built upon previous research where we documented significant LED light avoidance by the little brown bat (Myotis lucifugus) and big brown bat (Eptesicus fuscus) at an exurban study site in Connecticut, USA (Seewagen and Adams, 2021). Here, we experimentally tested the distances up to which that same LED lighting affects these species' presence and foraging activity and the composition of the foraging bat community to understand the reach of ALAN's influence on two light-averse North American bats. ...
... Our experimental design was as described in Seewagen and Adams (2021) except that we deployed three additional acoustic bat recorders at 25-m intervals away from the light array. We also mounted the lights and microphones 0.5 m higher to account for an increase in vegetation height in the wetland since the previous study and we did not include a treatment in which the lighting infrastructure was removed because we previously found no effect of the infrastructure alone on bat activity. ...
Artificial light at night (ALAN) is a global pollutant that disrupts circadian rhythmicity and a broad range of physiological processes and behaviors in animals. However, ALAN sensitivity can vary greatly even among closely related species and urgently needs study for much of the world's nocturnal wildlife, including bats. While an increasing number of bat species have recently been assessed for light tolerance, the spatial extent of ALAN's influence on bats has received little attention. This information need is a barrier to the protection of bats from ALAN in land-use planning and policy, and the development of best practices that effectively buffer bat habitat from light trespass. To help address this information gap for North America, we experimentally tested the distances up to which ALAN affects presence and activity of light-averse little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus), and the composition of a foraging bat assemblage in Connecticut, USA. We used three residential-scale, white, LED floodlights to expose bat foraging habitat to ALAN and compared acoustic activity of bats at distances of 0, 25, 50, and 75 m from the lights between nights when the lights were on versus off. Little brown bats were present on significantly fewer light than dark nights at every distance. Lighting significantly reduced little brown bat activity overall and at the farthest location from the lights (75 m), where it was only 43% of dark-night activity despite < 1 lx of illuminance. Presence of big brown bats was not significantly affected at any distance. Big brown bat activity on light nights averaged 48-75% of dark-night activity at each distance but was significantly lower only at 0 m. As expected , lighting had no effect on eastern red (Lasiurus borealis) or hoary bat (L. cinereus) presence or activity. Community composition on dark and light nights had an average dissimilarity of 38% and significantly differed at 0 m and 25 m. We conclude the type of ALAN we studied has a disturbance radius of at least 75 m for the little brown bat and up to 25 m for the big brown bat, with a resulting influence on community composition for up to 50 m. Cumulative habitat loss for the imperiled little brown bat caused by ALAN could therefore be substantial. We urge planners and natural resources regulators to consider these footprints when evaluating indirect impacts to bat habitat from current and future sources of ALAN across these species' ranges.
... Light at night can also affect foraging activities of nocturnal species. Since some species are more light tolerant than others, this can lead to shifts in community composition (Seewagen and Adams 2021). Road traffic also has an important toll on mammals, increasing road-kills in urban areas. ...
The United Arab Emirates (UAE) has had dramatic economic and population growth since its 1971 federation, with the built environment, green spaces, water features and other urban amenities growing to support its burgeoning population. These features, in turn, often provide unique habitats and microenvironments for a wide variety of resident and migratory species that benefit from their association with urban ecosystems, both on land and in nearshore coastal environments. While urbanization has undoubtedly caused important environmental challenges that should not be discounted, our growing cities have developed unique and important ecologies, much of which remains underappreciated and understudied in the UAE. Here we summarize the current understanding of urban ecology in the Emirates, providing insights into features that make cities amenable environments for organisms, particularly in the context of the UAE’s extreme environment. We also discuss several representative groups of organisms that benefit from the artificial environments provided by cities in both terrestrial and marine urban settings.
... The most widespread curtailment strategy is only based on a windspeed threshold below which the turbine is curtailed due to expected high bat activity. While curtailment has been shown to be efficient, its results remain variable and it does not fully reduce fatalities (Adams et al., 2021;Whitby et al., 2021). ...
... dusk and dawn) than during the rest of the night. However, the curtailment algorithm of Behr et al. (2017), which is now the standard method for mitigating bat collision risks of at wind farms in Germany, is one of the only algorithms we know of that consider bat diel activity patterns (Adams et al., 2021;Whitby et al., 2021). Adding an interaction between the time of the year and the time of the night could even increase the performance of such algorithms. ...
... Assessing the effect of replacing of old lighting technologies with LEDs on biodiversity should therefore be an urgent concern.McNaughton et al.(2021)found that a switch from HPS lamps to LEDs resulted in alterations of the timing of dawn song in birds, modifications in the avian community composition, an increase in avian species richness and an increase in ground insect activity.Likewise, found that LED light traps captured more insects than light traps fitted with HPS lamps. While some studies have shown a repulsive or attractive effect of LED lights on bats compared to dark sites(Rowse et al., 2018;Seewagen and Adams, 2021;Stone et al., 2012), to date, very few studies have focused on the impact of switching from old lighting technologies to LEDs on bats. ...
Electric lights have proliferated rapidly over the last century and have changed the night-time environment globally. Over the past decades, scientific studies have shown the effects of artificial light at night (ALAN) on biodiversity. Light pollution has been shown to disrupt a wide range of ecological processes and taxa. In this PhD, we aimed to fill some of the knowledge gaps that could prevent the effects of light pollution on biodiversity from being effectively addressed by mitigation measures. We used bats as model species because they are considered good indicators of the effect of anthropogenic pressures on biodiversity and because, being nocturnal, they are directly exposed to ALAN.We advocated considering the temporal distribution of species in conservation measures, a prerequisite being to have access to knowledge on their temporal ecology. We used data from a national bat monitoring program (Vigie-Chiro) based on acoustic monitoring to characterise bat diel activity patterns (9807 nights monitored, 20 species). We found that bat species could be separated into three functional groups characterised by a crepuscular activity, an activity that occurs when it is completely dark or an intermediate activity. We showed variations of diel activity patterns depending on the season. Accounting for these complex diel activity patterns would help to design efficient mitigation measures. For instance, it would allow the design of part-night lighting schemes covering the range of activity of the target species. Early emerging bats are mostly “light tolerant” species known to feed on insects attracted to lights. However, at the landscape scale, these species tend to be less abundant because of ALAN. This could be explained by disruptions in the diel activity patterns of bats due to ALAN, with potential consequences for population dynamics. Using the Vigie-Chiro dataset, we tested whether ALAN was responsible for such disruptions on a “light tolerant” species (Eptesicus serotinus). ALAN, and to a lesser extent moonlight, reduced its abundance. ALAN delayed activity, this delay was amplified during overcast nights, probably because cloud cover amplified skyglow. Further analyses suggested that two other “light tolerant” species might delay their activity because of ALAN. Thus, even “light tolerant” species should be protected from light pollution. Where it is not possible to switch off lights, other mitigation measures include changing the intensity, directionality and spectrum of light. Many countries are retrofitting lighting equipment with light emitting diodes (LEDs). Despite potential impacts on biodiversity, few studies have focused on this shift. By reanalysing the data from a previously published study, we found that changes in light spectrum and intensity during such a shift have additive and interactive effects on bats. Bat activity decreased with increasing LED intensity. Using the Vigie-Chiro dataset, we showed that the adoption of LEDs would decrease landscape connectivity for bats, with this impact possibly being mitigated by better orienting the light flux. We recommended using LEDs with warmer colours and reduced light intensity. Multiscale spatiotemporal approaches are needed to assess ALAN effect on biodiversity. Although some knowledge gaps remain, there is overwhelming evidence of the impact of light pollution on ecosystems. Mitigation measures are being developed, so there is a need to assess their effectiveness and possible improvements. Considering the reduction of ALAN at the landscape scale is a necessary next step, hence the emergence of the concept of dark ecological networks. A transdisciplinary project on lighting practices and their evolution in municipalities was initiated during this PhD. Indeed, as ALAN has not only ecological but also health and socio-cultural implications, a transdisciplinary perspective is needed to shift the paradigm from conventional lighting to new forms of lighting.
... Several radio-telemetry or GPS tracking studies have shown avoidance of well-illuminated areas in bat flights [18][19][20][21]. When experimentally introducing ALAN to naturally unlit environments, ALAN disrupted flight patterns and reduced activity in many species, regardless of the light source types (light-emitting diodes/LED, sodium pressure, or mercury vapor) of ALAN [22][23][24][25][26]. Acoustic studies that focused on ALAN in urban settings also found negative impacts of ALAN on bat commuting activity [27][28][29], even though urban bats might have adapted behaviorally to the city [30][31][32]. ...
... Very little is known about how North American bats respond to ALAN. A field experiment in Connecticut, USA, found that no bat species responded positively to ALAN when LED floodlights illuminated a dark nature preserve [24]. Similarly, another field experiment in the forest in Missouri, USA also found that most species avoided experimentally lit areas regardless of their foraging strategies except for the eastern red bat (Lasiurus borealis, species abbreviation LABO, [36,37]). ...
... No bat species in our study negatively responded to ALAN. Even though our results do not align with previous studies of ALAN and North American bats [24,36], they could be explained by the possibility that urbandwelling bats might have adapted to ALAN. Considering that previous studies of North American bats were conducted in areas where ALAN was generally absent, urban bats in our studies were very likely to respond to ALAN differently, which might be another example of urban wildlife adapting to a city life [30][31][32]. ...
Predators respond to the increase of prey by aggregation in space or foraging more often. However, foraging habitat suitability limits predators’ responses. For nocturnal insectivorous bats, artificial light at night (ALAN) can trigger insect prey aggregation. It is not clear how ALAN might affect predator-prey relationships in the urban setting, where urban bats could have adapted to the city, and novel spatial complexity introduced by man-made objects might alter foraging habitat suitability. We strategically selected sites to represent different levels of ALAN and spatial complexity. We recorded bat commuting and foraging activities and collected aerial insects to examine how ALAN and spatial complexity affected bat-insect relationships. We found that insect biomass was positively correlated with ALAN, but was not affected by spatial complexity. Large-sized big brown bats and hoary bats positively responded to change of prey in open sites whereas small-sized eastern red bats and silver-haired bats positively responded in cluttered sites, suggesting that the impact of ALAN could vary when ALAN is coupled with urban spatial complexity. Our study demonstrates that foraging habitat suitability can alter which species might benefit from ALAN. Predator-prey relationships in cities are complex, but general ecological principles still apply in novel urban ecosystems.
... In contrast [87,88], other research reported increased foraging activity near flood lights for Kuhl's pipistrelle bats (Pipistrellus kuhlii), a species that occurs throughout southern Europe, north Africa, and west Asia, suggesting the perception of light wavelength and/or foraging behavior as potential indicators for light's effect on bat species. Using acoustic monitoring in North America, Seewagen et al. [89] concluded that eastern red and hoary bats displayed no significant differences in activity between dark and LED-lit conditions. ...
Patterns of bat activity and mortalities at wind energy facilities suggest that bats are attracted to wind turbines based on bat behavioral responses to wind turbines. For example, current monitoring efforts suggest that bat activity increases post-wind turbine construction, with bats making multiple passes near wind turbines. We separated the attraction hypothesis into five previously proposed explanations of bat interactions at or near wind turbines, including attraction based on noise, roost sites, foraging and water, mating behavior, and lights, and one new hypothesis regarding olfaction, and provide a state of the knowledge in 2022. Our review indicates that future research should prioritize attraction based on social behaviors, such as mating and scent-marking, as this aspect of the attraction hypothesis has many postulates and remains the most unclear. Relatively more data regarding attraction to wind turbines based on lighting and noise emission exist, and these data indicate that these are unlikely attractants. Analyzing attraction at the species-level should be prioritized because of differences in foraging, flight, and social behavior among bat species. Lastly, research assessing bat attraction at various scales, such as the turbine or facility scale, is lacking, which could provide important insights for both wind turbine siting decisions and bat mortality minimization strategies. Identifying the causes of bat interactions with wind turbines is critical for developing effective impact minimization strategies.
