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Dose-dependent responses of avian daily rhythms to artificial light at night

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... Birds use light cues for synchronizing their biological rhythms [5] and ALAN can alter their photoperiodic perception [6][7][8][9]. Consequently, ALAN can affect the timing of reproductive physiology and behaviour [8,10,11], timing of dawn singing [10,12,13] and sleep behaviour [14] of freeliving passerine songbird species. Experimental studies on captive songbirds have confirmed work in the wild [7,15]. ...
... Consequently, ALAN can affect the timing of reproductive physiology and behaviour [8,10,11], timing of dawn singing [10,12,13] and sleep behaviour [14] of freeliving passerine songbird species. Experimental studies on captive songbirds have confirmed work in the wild [7,15]. Blackbirds increase locomotor activity at night when roosting under light compared with darkness [15]. ...
... Blackbirds increase locomotor activity at night when roosting under light compared with darkness [15]. Similarly, great tits advance activity, delay activity offset, and move a higher proportion of their daily activity into the night when exposed to ALAN [7]. ...
Article
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Artificial light at night (ALAN) is an increasing phenomenon associated with worldwide urbanization. In birds, broad-spectrum white ALAN can have disruptive effects on activity patterns, metabolism, stress response and immune function. There has been growing research on whether the use of alternative light spectra can reduce these negative effects, but surprisingly, there has been no study to determine which light spectrum birds prefer. To test such a preference, we gave urban and forest great tits (Parus major) the choice where to roost using pairwise combinations of darkness, white light or green dim light at night (1.5 lux). Birds preferred to sleep under artificial light instead of darkness, and green was preferred over white light. In a subsequent experiment, we investigated the consequence of sleeping under a particular light condition, and measured birds' daily activity levels, daily energy expenditure (DEE), oxalic acid as a biomarker for sleep debt and cognitive abilities. White light affected activity patterns more than green light. Moreover, there was an origin-dependent response to spectral composition: in urban birds, the total daily activity and night activity did not differ between white and green light, while forest birds were more active under white than green light. We also found that individuals who slept under white and green light had higher DEE. However, there were no differences in oxalic acid levels or cognitive abilities between light treatments. Thus, we argue that in naive birds that had never encountered light at night, white light might disrupt circadian rhythms more than green light. However, it is possible that the negative effects of ALAN on sleep and cognition might be observed only under intensities higher than 1.5 lux. These results suggest that reducing the intensity of light pollution as well as tuning the spectrum towards long wavelengths may considerably reduce its impact.
... Urban birds were selected as the focal species in this research. ALAN pollution has a significant impact on the organismal functions of birds because it disrupts their internal clock and circadian rhythm (Dominoni et al., 2013), even when the intensity is as low as 0.05lux (de Jong et al., 2016a). The melatonin levels in birds were found to decrease with the increase in ALAN intensity (de Jong et al., 2016a). ...
... ALAN pollution has a significant impact on the organismal functions of birds because it disrupts their internal clock and circadian rhythm (Dominoni et al., 2013), even when the intensity is as low as 0.05lux (de Jong et al., 2016a). The melatonin levels in birds were found to decrease with the increase in ALAN intensity (de Jong et al., 2016a). White ALAN will cause sleep deprivation and stress response in birds (Ouyang et al., 2017). ...
... Indirect effects indicate that ALAN attracts prey species, which consequently may change the activities of birds such as foraging and flight (de Jong et al., 2016b;Spoelstra et al., 2015). Several bird species have been proven to use ALAN to extend foraging into the night and advance the onset of daily activities compared with conspecifics in dark areas (Klenke, 2015), and this trend became more pronounced as the ALAN intensity increased (de Jong et al., 2016a). Hence, urban bird activities at night can be divided into active (forage and flight) and non-active (sleep) (Dominoni et al., 2014). ...
... In many animals (including humans), nocturnal melatonin production is sensitive to light [7], even at low levels of light [1], thereby disrupting the circadian rhythm. This disruption can be either in the form of reductions in melatonin levels or in shifts in rhythms [15]. As the melatonin pathway has peak sensitivity in the blue region [16], exposure to ALAN rich in blue wavelength has a higher potential of melatonin suppression. ...
... Out of 10 studies included in the review, only five were explicitly designed to test the hypothesis that ALAN suppresses melatonin in birds (Table 4). These studies used five different Passeriformes species: Eurasian blackbird (Turdus merula) [96], western scrub-jay (Aphelocoma californica) [97], great tit (Parus major) [15], Indian weaver bird (Ploceus philippinus) [98], and Eurasian tree sparrow (Passer montanus) [99]. The other five studies used an experimental dim illumination at night in the context of circadian rhythms research [100][101][102] and/or photoperiodism [103,104]. ...
... The intensity and exposure of ALAN varied greatly between studies. The experiments that were explicitly designed to test for the effects of ALAN on behavior and physiology of birds used a light intensity that ranged from 0.3 lx [96] to 2 lx [98], 3.2 lx [97], 5 lx [15], and 8 lx [99]. Two studies used a single level of light intensity applied constantly throughout the night [96,97]. ...
Article
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Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin-the "hormone of darkness" and a key player in circadian regulation-can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01-0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower, wavelength-dependent intensities are implied by some studies and require rigorous testing in ecological contexts. In many studies, melatonin suppression occurs at the minimum light levels tested, and, in better-studied groups, melatonin suppression is reported to occur at lower light levels. We identify major research gaps and conclude that, for most groups, crucial information is lacking. No studies were identified for amphibians and reptiles and long-term impacts of low-level ALAN exposure are unknown. Given the high sensitivity of vertebrate melatonin production to ALAN and the paucity of available information, it is crucial to research impacts of ALAN further in order to inform effective mitigation strategies for human health and the wellbeing and fitness of vertebrates in natural ecosystems.
... It can increase the spatial resistance, cause habitat fragmentation for various organisms (Table 3) and deteriorate the suitability of habitat for migrating species (Table 4). While there is empirical evidence from laboratory and experimental studies that light level comparable to urban skyglow has adverse effects on organisms (e.g., references [86,109,286]), there is as of yet only limited evidence from field monitoring (e.g., references [253,287]). ...
... Feeding places for songbirds are being visited longer [217] and in higher numbers [300]. Prolongation of the daily activity of songbirds was observed [67,97,101,103,104], and the extended activity phase correlated with the level of luminance in many birds such as robins, chaffinches, blackbirds, great and blue tits [286]. At lit beaches, waders have been observed hunting for sandworms even after dark [95]. ...
... However, one of the most effective methods to limit or reduce the adverse effects of ALAN is to reduce the light intensity. (e.g., references [54,286,303]). ...
Article
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The fundamental change in nocturnal landscapes due to the increasing use of artificial light at night (ALAN) is recognized as being detrimental to the environment and raises important regulatory questions as to whether and how it should be regulated based on the manifold risks to the environment. Here, we present the results of an analysis of the current legal obligations on ALAN in context with a systematic review of adverse effects. The legal analysis includes the relevant aspects of European and German environmental law, specifically nature conservation and immission control. The review represents the results of 303 studies indicating significant disturbances of organisms and landscapes. We discuss the conditions for prohibitions by environmental laws and whether protection gaps persist and, hence, whether specific legislation for light pollution is necessary. While protection is predominantly provided for species with special protection status that reveal avoidance behavior of artificially lit landscapes and associated habitat loss, adverse effects on species and landscapes without special protection status are often unaddressed by existing regulations. Legislative shortcomings are caused by difficulties in proving adverse effect on the population level, detecting lighting malpractice, and applying the law to ALAN-related situations. Measures to reduce ALAN-induced environmental impacts are highlighted. We discuss whether an obligation to implement such measures is favorable for environmental protection and how regulations can be implemented.
... Disturbance of natural light environment would cause birds to alter flight behaviors, activity rhythms or physiological functions Grubisic et al. 2019;Sanders et al. 2021). There is accumulating evidence showing the disruptive effects of artificial light on birds, including collisions (Jones and Francis 2003;Gehring et al. 2009;Zhao et al. 2014Zhao et al. , 2020, interferences of magnetic orientations (Wiltschko et al. 1993(Wiltschko et al. , 2001(Wiltschko et al. , 2008Pinzon-Rodriguez and Muheim 2017;Nießner et al. 2018), disruptions of circadian and circannual rhythms (Ziegler et al. 2021;Kempenaers et al. 2010;Dominoni et al. 2013aDominoni et al. , 2013bDominoni et al. , 2020bDa Silva et al. 2015) and interventions of hormone levels (Ziegler et al. 2021;Ouyang et al. 2015;de Jong et al. 2016;Alaasam et al. 2018;Grunst et al. 2020;Jiang et al. 2020;Moaraf et al. 2020). Sleep is an essential circadian function and is fundamental for birds' energy conservation (Roth et al. 2010;Vorster and Born 2015). ...
... The effect of light does not only confine to advancing activity in the morning, but in some circumstances delays the end of daytime activity at dusk. A study on Great tits showed white light postponed daytime activity offset as intensity increased, and the delaying effect maximally reached half an hour at 5 lux (de Jong et al. 2016). A more recent study on Great tits showed that the forest birds delayed daytime activity offset under 1.5 lux white light by 19 min., either in the treatment with light only or with both light and noise (Dominoni et al. 2020a). ...
... Yet, the exact sleeping rhythm of birds under natural light still needs to be explored through studies in longer periods. The delaying effect of artificial light on sleep onset of Chestnut buntings is in line with the laboratory studies which showed artificial light caused a later daytime activity offset of Great tits (de Jong et al. 2016) or Blue tits . However, the magnitudes of delaying effect were different. ...
Article
Artificial light owns a rapid-expanding pattern, which may disrupt the sleep behaviors of birds roosting in illuminated urban areas. Whether the birds’ sleep would variably be affected by light with different wavelengths or intensities has not been broadly explored, and the species in Eastern China have rarely been investigated. The study chose Chestnut buntings that are a common migratory species flying via Eastern China as the subjects and investigated their sleep in response to five light spectrums at three ecologically relevant intensities. It shows that artificial light mainly delayed sleep onset, reduced sleep duration and increased frequency of awakenings, which to the largest degrees resulted in a 3-h delay of sleep onset, 25% reduction of sleep and 0.31 times/h more nocturnal awakenings. Awakening time was delayed at higher light intensity while being advanced in dimmed light. The effect of light spectrums overall ranked from the most to the least as 510 nm green, 580 nm yellow or white, and 470 nm blue or 620 nm orange light; the sleep parameters were affected more with higher light intensities. The study highlights the potential of adjusting spectral compositions of light source to mitigate the disturbance of artificial light to avian sleep.
... Artificial light at night (ALAN) is increasing worldwide by about 3-6% annually [1], with more than 80% of the world population living under lightpolluted skies [2]. Awareness of the harmful effects of ALAN on living organisms is also increasing [3,4], including reports of changes in the length and quality of sleep [5,6], and in temporal activity shifts in mammals [5,7,8], birds [6,9,10], anurans [11] and marine species [12,13]. In insects, ALAN-induced changes in foraging activity could lead to higher predation risk [14,15], possible nocturnal or crepuscular way of life [26,27]. ...
... Despite increasing concern regarding the harmful effects of ALAN on humans and other animals [18,[52][53][54], there is still insufficient knowledge regarding its impact on insects, which constitute a major bio-indicator of environmental changes and pollution [55,56]. The ALAN intensities investigated here had been previously reported as prevalent and ecologically relevant in urban environments, affecting the behaviour and ecology of various species [5,9,17,54,57], as well as having a 'sink' effect on flying insects attracted towards street lights [3,18,20,58,59]. We explored the effect of ALAN on two key behaviours: locomotion, which is important in foraging; and stridulation, which is a major component of the cricket's courtship behaviour, sexual selection and intraspecific communication [60][61][62][63][64][65][66]. ...
Article
Full-text available
Living organisms experience a worldwide continuous increase in artificial light at night (ALAN), negatively affecting their behaviour. The field cricket, an established model in physiology and behaviour, can provide insights into the effect of ALAN on insect behaviour. The stridulation and loco-motion patterns of adult male crickets reared under different lifelong ALAN intensities were monitored simultaneously for five consecutive days in custom-made anechoic chambers. Daily activity periods and acro-phases were compared between the experimental groups. Control crickets exhibited a robust rhythm, stridulating at night and demonstrating locomotor activity during the day. By contrast, ALAN affected both the relative level and timing of the crickets' nocturnal and diurnal activity. ALAN induced free-running patterns, manifested in significant changes in the median and variance of the activity periods, and even arrhythmic behaviour. The magnitude of disruption was light intensity dependent, revealing an increase in the difference between the activity periods calculated for stridu-lation and locomotion in the same individual. This finding may indicate the existence of two peripheral clocks. Our results demonstrate that ecologically relevant ALAN intensities affect crickets' behavioural patterns, and may lead to decoupling of locomotion and stridulation behaviours at the individual level, and to loss of synchronization at the population level.
... Light-emitting diodes covering a wide spectrum (450 < λ < 700 nm) affect daily rhythms of locomotor activity, body temperature, singing and sleep (duration and quality), night-time production of melatonin, proliferation of brain stem cells, immunity and oxidative stress markers, as reported in several species, including the Great Tit Parus major Raap et al., 2015Raap et al., , 2016ade Jong et al., 2016ade Jong et al., , 2017Raap, 2018), Blackbird Turdus merula (Dominoni et al., 2013b), Indian Weaver Bird Ploceus philippinus (Kumar et al., 2018), Japanese Quail Coturnix japonica, chicken G. domesticus and King Quail Excalfactoria chinesis (Saini C. et al., 2019), Zebra Finches Taeniopygia guttata (Moaraf et al., 2020), and Weaver Ploceus philippinus (Singh et al., 2012). In laboratory experiments the effects were dose-dependent (0.05 to 5 lx) and varied with the spectral composition (de Jong et al., 2016a(de Jong et al., , 2017. ...
... Light-emitting diodes covering a wide spectrum (450 < λ < 700 nm) affect daily rhythms of locomotor activity, body temperature, singing and sleep (duration and quality), night-time production of melatonin, proliferation of brain stem cells, immunity and oxidative stress markers, as reported in several species, including the Great Tit Parus major Raap et al., 2015Raap et al., , 2016ade Jong et al., 2016ade Jong et al., , 2017Raap, 2018), Blackbird Turdus merula (Dominoni et al., 2013b), Indian Weaver Bird Ploceus philippinus (Kumar et al., 2018), Japanese Quail Coturnix japonica, chicken G. domesticus and King Quail Excalfactoria chinesis (Saini C. et al., 2019), Zebra Finches Taeniopygia guttata (Moaraf et al., 2020), and Weaver Ploceus philippinus (Singh et al., 2012). In laboratory experiments the effects were dose-dependent (0.05 to 5 lx) and varied with the spectral composition (de Jong et al., 2016a(de Jong et al., , 2017. In urban areas with conventional street lighting, whenever possible tits avoided night-time illumination (de Jong et al., 2016b). ...
Article
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The present review draws together wide-ranging studies performed over the last decades that catalogue the effects of artificial-light-at-night (ALAN) upon living species and their environment. We provide an overview of the tremendous variety of light-detection strategies which have evolved in living organisms - unicellular, plants and animals, covering chloroplasts (plants), and the plethora of ocular and extra-ocular organs (animals). We describe the visual pigments which permit photo-detection, paying attention to their spectral characteristics, which extend from the ultraviolet into infrared. We discuss how organisms use light information in a way crucial for their development, growth and survival: phototropism, phototaxis, photoperiodism, and synchronization of circadian clocks. These aspects are treated in depth, as their perturbation underlies much of the disruptive effects of ALAN. The review goes into detail on circadian networks in living organisms, since these fundamental features are of critical importance in regulating the interface between environment and body. Especially, hormonal synthesis and secretion are often under circadian and circannual control, hence perturbation of the clock leads to hormonal imbalance. The review addresses how the ubiquitous introduction of light-emitting diode technology may exacerbate, or in some cases reduce, the generalized ever-increasing light pollution. Numerous examples are given of how widespread exposure to ALAN is perturbing many aspects of plant and animal behaviour and survival: foraging, orientation, migration, seasonal reproduction, colonization and more. We examine the potential problems at the level of individual species and populations and extend the debate to the consequences for ecosystems. We stress, through a few examples, the synergistic harmful effects resulting from the impacts of ALAN combined with other anthropogenic pressures, which often impact the neuroendocrine loops in vertebrates. The article concludes by debating how these anthropogenic changes could be mitigated by more reasonable use of available technology – for example by restricting illumination to more essential areas and hours, directing lighting to avoid wasteful radiation and selecting spectral emissions, to reduce impact on circadian clocks. We end by discussing how society should take into account the potentially major consequences that ALAN has on the natural world and the repercussions for ongoing human health and welfare.
... In the last decade, numerous studies have reported the effects of ALAN on many physiological processes in a large panel of animals. This anthropogenic light modifies illuminance levels so that the perception of fine changes in natural light level can be impaired, thus desynchronizing daily or seasonal activities (Robert et al., 2015;de Jong et al., 2016). Hence, the internal circadian timekeeping system is impacted by ALAN mainly through alterations in the expression of clock genes (Bedrosian et al., 2013;Fonken et al., 2013;Honnen et al., 2016Honnen et al., , 2019Khan et al., 2018). ...
... The higher the ALAN illuminance, the greater the deregulation of transcriptome expression. This observation had previously been noted in several species exposed to a range of ALAN levels on biological processes, such as hormonal synthesis (Brüning et al., 2015;Grubisic et al., 2019;Kupprat et al., 2020), activity rhythms (de Jong et al., 2016;Barré et al., 2020;Secondi et al., 2021), reproductive physiology (Dominoni et al., 2018), and individual's abundance (Sanders et al., 2018). More specifically, our high light intensity at night (5 lx) left a strong impact on diurnal gene expression, while our low light intensity at night (0.1 lx) left a weak impact on diurnal gene expression. ...
Preprint
Artificial light at night (ALAN) affects numerous physiological and behavioural mechanisms in various species by potentially disturbing circadian timekeeping systems. Although gene-specific approaches have already shown the deleterious effect of ALAN on the circadian clock, immunity and reproduction, large-scale transcriptomic approaches with ecologically relevant light levels are still lacking to assess the global impact of ALAN on biological processes. Moreover, studies have focused mainly on variations in gene expression during the night in the presence of ALAN but never during the day. In a controlled laboratory experiment, transcriptome sequencing of Bufo bufo tadpoles revealed that ALAN affected gene expression at both night and daytime with a dose-dependent effect and globally induced a downregulation of genes. ALAN effects were detected at very low levels of illuminance (0.1 lux) and affected mainly genes related to the innate immune system and, to a lesser extend to lipid metabolism. These results indicate that a broad range of physiological pathways is impacted at the molecular level by very low levels of ALAN potentially resulting in reduced survival under environmental immune challenges.
... We exposed female zebra finches to ALAN for 7 weeks, and compared the recruitment of new neurons and total neuronal densities in selected brain regions (MSt, NC, HC) with control birds that were kept under dark nights. The ALAN intensity that we used was 5 lux, as it is ecologically relevant to birds [22,23] and had the greatest effect on cell proliferation in the VZ in our previous study [8]. In addition, in the present study, ALAN exposure was longer than in our previous one, to allow enough time for the new neurons to arrive at their final destination, and to check whether the previous exposure to ALAN was too short for the brain to reach an equilibrium between neuronal death and compensatory neuronal recruitment. ...
... Nocturnal MEL levels under ALAN conditions were significantly lower compared to control birds that were exposed to dark nights (Figure 4), similar to previous reports in zebra finches [8,47], as well as in other bird species [23], diurnal mammals [48], and fish [49]. Evidently, very low ALAN intensities can suppress MEL biosynthesis not only in nocturnal [50], but also in diurnal species. ...
Article
Full-text available
Despite growing evidence that demonstrate adverse effects of artificial light at night (ALAN) on many species, relatively little is known regarding its effects on brain plasticity in birds. We recently showed that although ALAN increases cell proliferation in brains of birds, neuronal densities in two brain regions decreased, indicating neuronal death, which might be due to mortality of newly produced neurons or of existing ones. Therefore, in the present study we studied the effect of long-term ALAN on the recruitment of newborn neurons into their target regions in the brain. Accordingly, we exposed zebra finches (Taeniopygia guttata) to 5 lux ALAN, and analysed new neuronal recruitment and total neuronal densities in several brain regions. We found that ALAN increased neuronal recruitment, possibly as a compensatory response to ALAN-induced neuronal death, and/or due to increased nocturnal locomotor activity caused by sleep disruption. Moreover, ALAN also had a differential temporal effect on neuronal densities, because hippocampus was more sensitive to ALAN and its neuronal densities were more affected than in other brain regions. Nocturnal melatonin levels under ALAN were significantly lower compared to controls, indicating that very low ALAN intensities suppress melatonin not only in nocturnal, but also in diurnal species.
... Typically, urban birds are active earlier in the day and in the season compared to rural counterparts (Miller, 2006;Da Silva et al., 2015). Sometimes, differences in the morning are followed by differences in the rest of the day: short or disturbed nights may be compensated with a nap (Raap et al., 2016) or with just lower activity levels during daytime (de Jong et al., 2016). This may yield further divergence in daily activity patterns between birds of different habitats. ...
... This pattern is, as far as we know, the first time this has been shown at this scale, but may indicate that rising early is associated with inserting periods of no or low activity more often during the rest of the day (c.f. de Jong et al., 2016;Raap et al., 2016). Our data are in line with the growing awareness that the presence of human settlements and infrastructure can alter environmental cues and make urban and rural birds of the same species alter their activity patterns over the day. ...
Article
Full-text available
Human settlements and activities alter the natural environment acoustically and visually. Traffic noise and street lights are two of the most prominent pollutants which may affect animal activity patterns. Birds in urban areas have been reported to sing nocturnally and to have an earlier dawn chorus compared to their rural counterparts. However, few studies have measured whether singing more at night or earlier in the morning means singing less during daytime. It is therefore unclear whether they shift or extend or overall increase their activities. Furthermore, few studies on anthropogenic noise-related shifts in song activity replicated well at the habitat level. We recorded singing activity in urban and rural great tits (Parus major) for 24 h and sampled 11 urban–rural pairs of territories, inside and outside 11 different cities across the Netherlands. We found that urban birds sing earlier during the day, have similar singing effort in the dawn chorus, but sing less than rural birds during the rest of the day. The shift in timing between urban and rural birds was 22 min on average and resulted in more songs for urban birds during a less noisy time of the day. The lower singing activity over the day made that urban birds sang less when it was more noisy compared to the natural rhythm of rural great tits. We currently lack insight into whether these differences yield any positive or negative fitness consequences, but it is a clear case of how anthropogenic effects on the natural environment influence fundamental aspects of daily life in the animal communities with which we share the urban habitat.
... However, the physiological and behavioral effects of ALAN on birds may not be consistent across species. For example, studies have shown that adult great tits (Parus major) wake up earlier and sleep less (de Jong et al., 2016a;Raap et al., 2015;Ouyang et al., 2017) and their nestlings grow more slowly (de Jong et al., 2015;Raap et al., 2016a) when being exposed to stronger ALAN; in contrast, similar effects are not observed in a closely related species, the blue tit (Cyanistes caeruleus; Sun et al., 2017), or another cavity-nesting bird, the pied flycatcher (Ficedula hypoleuca;de Jong et al., 2015). In addition, ALAN is found to prolong the feeding time of parent birds after sunset in northern mockingbirds (Mimus polyglottos; Stracey et al., 2014), but not in great tits (Titulaer et al., 2012). ...
... Barn swallows (Hirundo rustica) are one of the most widespread passerines likely because they nest on man-made structures (Turner and Rose, 1989;Smith et al., 2018), including those in urban areas (e.g., Wang and Hung, 2019;Zhao et al., 2020). ALAN intensity in cities is particularly high that may induce behavioral changes in birds living in urban areas (Dominoni et al., 2013;de Jong et al., 2016a;de Jong et al., 2016b). In addition, barn swallows sleep and raise their offspring in open nests that are often built nearby streetlight in cities (Fig. 1), making the species directly exposed to ALAN. ...
Article
Full-text available
Understanding how artificial light at night (ALAN) impacts wildlife is increasingly important because more and more species are colonizing urban areas. As most of the bird studies on ALAN use controlled light set inside or around nest-boxes, the ecological effect of ALAN resulting from in situ streetlight on birds remains contentious. The barn swallow (Hirundo rustica) often builds open nests on buildings, which are directly exposed to varying intensity of ALAN, and thus provides a good system to examine the effect of in situ ALAN on birds. By examining the nest-site selection, reproductive success and behavior of barn swallows under various ALAN intensity in Taipei City, we found a positive effect of ALAN on their fledging success; nonetheless, such effect was only found in the swallows' first brood, but not second one. We also found that parent birds in the nests with higher ALAN intensity had higher feeding rates and more extended feeding time past sunset, which were likely stimulated by the increased begging behavior of their chicks. The night-feeding behavior might contribute to the increased fledging success, especially at the early breeding season. Interestingly, despite of the reproductive benefits obtained from ALAN, we found that the barn swallows did not select nest sites regarding ALAN intensity. The weak nest-site selection perhaps result from the complex life history interactions involving ALAN and/or confounding factors associated with ALAN in cities. This study improves our understanding of how urban birds, especially open-nesting ones, respond to in situ ALAN and provides useful information for developing urban conservation strategies.
... In the last decade, numerous studies have reported the effects of ALAN on many physiological processes in a large panel of animals. This anthropogenic light modifies illuminance levels so that the perception of fine changes in natural light level can be impaired, thus desynchronizing daily or seasonal activities (Robert et al., 2015;de Jong et al., 2016). Hence, the internal circadian timekeeping system is impacted by ALAN mainly through alterations in the expression of clock genes (Bedrosian et al., 2013;Fonken et al., 2013;Honnen et al., 2016Honnen et al., , 2019Khan et al., 2018). ...
... The higher the ALAN illuminance, the greater the deregulation of transcriptome expression. This observation had previously been noted in several species exposed to a range of ALAN levels on biological processes, such as hormonal synthesis (Brüning et al., 2015;Grubisic et al., 2019;Kupprat et al., 2020), activity rhythms (de Jong et al., 2016;Barré et al., 2020;Secondi et al., 2021), reproductive physiology (Dominoni et al., 2018), and individual's abundance (Sanders et al., 2018). More specifically, our high light intensity at night (5 lx) left a strong impact on diurnal gene expression, while our low light intensity at night (0.1 lx) left a weak impact on diurnal gene expression. ...
Article
Artificial light at night (ALAN) affects numerous physiological and behavioural mechanisms in various species by potentially disturbing circadian timekeeping systems and modifying melatonin levels. However, given the multiple direct and indirect effects of ALAN on organisms, large-scale transcriptomic approaches are essential to assess the global effect of ALAN on biological processes. Moreover, although studies have focused mainly on variations in gene expression during the night in the presence of ALAN, it is necessary to investigate the effect of ALAN on gene expression during the day. In this study, we combined de novo transcriptome sequencing and assembly, and a controlled laboratory experiment to evaluate the transcriptome-wide gene expression response using high-throughput (RNA-seq) in Bufo bufo tadpoles exposed to ecologically relevant light levels. Here, we demonstrated for the first time that ALAN affected gene expression at night (3.5% and 11% of differentially expressed genes when exposed to 0.1 and 5 lx compared to controls, respectively), but also during the day (11.2% of differentially expressed genes when exposed to 5 lx compared to controls) with a dose-dependent effect. ALAN globally induced a downregulation of genes (during the night, 58% and 62% of the genes were downregulated when exposed to 0.1 and 5 lx compared to controls, respectively, and during the day, 61.2% of the genes were downregulated when exposed to 5 lx compared to controls). ALAN effects were detected at very low levels of illuminance (0.1 lx) and affected mainly genes related to the innate immune system and, to a lesser extend to lipid metabolism. These results provide new insights into understanding the effects of ALAN on organism. ALAN impacted the expression of genes linked to a broad range of physiological pathways at very low levels of ALAN during night-time and during daytime, potentially resulting in reduced immune capacity under environmental immune challenges.
... By disrupting natural light cycles, artificial light can disrupt daily rhythms of behavior and physiology in humans and wildlife (Stevens and Zhu, 2015;Dominoni et al., 2016). Effects on behavior are particularly well-documented for diurnal birds, which often show earlier onset of daily activity (Kempenaers et al., 2010;Dominoni et al., 2013b;Da Silva et al., 2014;de Jong et al., 2017;Spoelstra et al., 2018;Ulgezen et al., 2019) and increased night-time activity (Dominoni et al., 2013a;de Jong et al., 2016de Jong et al., , 2017Ouyang et al., 2017;Alaasam et al., 2018;Ulgezen et al., 2019) when exposed to light at night. These behavioral changes may arise as a direct result of artificial light enhancing the visual environment, leading diurnal animals to forage more at night (Russ et al., 2014) or become more vigilant (Yorzinski et al., 2015). ...
... The effects of ecologically-realistic artificial lighting on sleep are seldom tested; most studies have been on captive or laboratory animals, with relatively few exceptions (Aulsebrook et al., 2018). Although animals exposed to lights inside a cage or nest box show reduced sleep behavior and night-time rest (Raap et al., 2015;Yorzinski et al., 2015;de Jong et al., 2016;Raap et al., 2016;de Jong et al., 2017;Alaasam et al., 2018), it is unclear whether, in real-world, heterogeneously-lit environments, animals would inhabit such intensely-lit spaces in the first place (Yorzinski et al., 2015;Aulsebrook et al., 2018;Raap et al., 2018;Caorsi et al., 2019). To address these gaps in the literature, we conducted our study in a large, naturalistic, heterogeneously-lit outdoor environment, where birds could limit their exposure to artificial lights by moving to less-lit areas at night. ...
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Artificial light at night could have widespread and detrimental impacts on sleep. To reduce disruptive effects of artificial light on sleep in humans, most smartphones and computers now have software that reduces blue light emissions at night. Little is known about whether reducing blue light emissions from city lights could also benefit urban wildlife. We investigated the effects of blue-rich (white) and blue-reduced (amber) LED streetlights on accelerometry-defined rest, electrophysiologically-identified sleep, and plasma melatonin in a diurnal bird, the black swan (Cygnus atratus). Urban swans were exposed to 20 full nights of each lighting type in an outdoor, naturalistic environment. Contrary to our predictions, we found that night-time rest was similar during exposure to amber and white lights but decreased under amber lights compared with dark conditions. By recording brain activity in a subset of swans, we also demonstrated that resting birds were almost always asleep, so amber light also reduced sleep at night. We found no effect of light treatment on total (24 h) daily rest or plasma melatonin. Our study provides the first electrophysiologically-verified evidence for effects of streetlights on sleep in an urban animal, and furthermore suggests that reducing blue wavelengths of light might not mitigate these effects.
... However, during a full moon, sleep in geese did not vary with cloud cover, likely because the light from artificially illuminated clouds was similar to moonlight. Numerous studies also found that when exposed to artificial light at night, birds show increased activity [44,55,[66][67][68][69][70][71][72][73], delayed chirping behavior [74], increased vigilance [75] and reduced sleep behavior at night [43,[76][77][78][79], but see [80,81]. There is some evidence that these changes in behavior are associated with reduced circulating oxalate [66,79], a biomarker of sleep debt in rats and humans [82]. ...
... The peak in non-REM sleep intensity also appeared delayed, which further suggests some physiological disruption of sleep regulation. Other research demonstrates that urban intensities of light at night (0.03 to 8 lux) can suppress circulating melatonin concentrations [55,68,72,89] and alter expression of clock genes [79], suggesting that circadian pathways could mediate some of the effects of artificial light at night on sleep. Together, these findings suggest that artificial light can influence sleep both directly and indirectly, and that the importance of various pathways might vary depending on the species or context. ...
Article
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Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light on sleep and subsequent performance in birds. There is accumulating evidence that exposure to natural and artificial sources of light regulates and suppresses sleep in diurnal birds. Sleep also benefits avian cognitive performance, including during early development. Nevertheless, multiple studies suggest that light can prolong wakefulness in birds without impairing performance. Although there is still limited research on this topic, these results raise intriguing questions about the adaptive value of sleep. Further research into the links between light, sleep and performance, including the underlying mechanisms and consequences for fitness, could shed new light on sleep evolution and urban ecology.
... ALAN was shown to alter behavioral responses during flight, migration, rest, and active periods during both night and day, as well during breeding periods and the egg-laying process [169][170][171]. Furthermore, ALAN was reported to impact physiological responses that involved altered reproduction [172], development [173,174], body mass [175], and hormonal levels [176][177][178][179]. ...
... major) [174], elevated corticosterone hormone in great tits (P. major), accelerated reproductive endocrine activation of the hypothalamic-pituitary-gonadal axis in tree sparrows (Passer montanus), low levels of estradiol in female and male scrub-jays (Aphelocoma coerulescens) [176], an earlier increase of luteinizing hormone, a lower peak in the secretion of luteinizing hormone, lowered levels of testosterone and estradiol in urban tree sparrows exposed to ALAN, and lowered or suppressed melatonin levels [177][178][179]. ...
Article
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The application of lighting technologies developed in the 20th century has increased the brightness and changed the spectral composition of nocturnal night-time habitats and night skies across urban, peri-urban, rural, and pristine landscapes, and subsequently, researchers have observed the disturbance of biological rhythms of flora and fauna. To reduce these impacts, it is essential to translate relevant knowledge about the potential adverse effects of artificial light at night (ALAN) from research into applicable urban lighting practice. Therefore, the aim of this paper is to identify and report, via a systematic review, the effects of exposure to different physical properties of artificial light sources on various organism groups, including plants, arthropods, insects, spiders, fish, amphibians, reptiles, birds, and non-human mammals (including bats, rodents, and primates). PRISMA 2020 guidelines were used to identify a total of 1417 studies from Web of Science and PubMed. In 216 studies, diverse behavioral and physiological responses were observed across taxa when organisms were exposed to ALAN. The studies showed that the responses were dependent on high illuminance levels, duration of light exposure, and unnatural color spectra at night and also highlighted where research gaps remain in the domains of ALAN research and urban lighting practice.To avoid misinterpretation, and to define a common language, key terminologies and definitions connected to natural and artificial light have been provided. Furthermore, the adverse impacts of ALAN urgently need to be better researched, understood, and managed for the development of future lighting guidelines and standards to optimize sustainable design applications that preserve night-time environment(s) and their inhabiting flora and fauna.
... Most studies to date have focused on the comparison between organisms or habitats exposed or not to ALAN, overlooking the main characteristics of artificial light, including first and foremost light intensity (but see de Jong et al. 2016;Ouyang et al. 2017;Brüning et al. 2018). Intuitively, the potential of this stressor to alter natural habitats and species would be severe at high intensities and in the immediate vicinity of light sources, but likely less so at low intensities and farther away from those sources. ...
... In this line, Gaston et al. (2015) recently concluded that one of the most important challenges in ALAN studies is determining thresholds and species dose-response functions. One of the few published examples is a study on the bird Parus major, in which researchers documented a strong dose-dependent response to ALAN in the activity pattern and melatonin level production of this species, without an obvious threshold of light intensity (de Jong et al. 2016). Similarly, Riley et al. (2015) studied the effect of various light intensities on the dispersal timing of Atlantic salmon fry (Salmo salar). ...
Article
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Artificial Light at Night (ALAN) is expanding worldwide, and the study of its influence remains limited mainly to documenting impacts, overlooking the variation in key characteristics of the artificial light such as its intensity. The potential dose–response of fitness-related traits to different light intensities has not been assessed in sandy beach organisms. Hence, this study explored dose-responses to ALAN by exposing the intertidal sandy beach isopod Tylos spinulosus to a range of light intensities at night: 0 (control), 20, 40, 60, 80 and 100 lx. We quantified the response of this species at the molecular (RNA:DNA ratios), physiological (absorption efficiency) and organismal (growth rate) levels. Linear and non-linear regressions were used to explore the relationship between light intensity and the isopod response. The regressions showed that increasing light intensity caused an overall ~ threefold decline in RNA:DNA ratios and a ~ threefold increase in absorption efficiency, with strong dose-dependent effects. For both response variables, non-linear regressions also identified likely thresholds at 80 lx (RNA:DNA) and 40 lx (absorption efficiency). By contrast, isopod growth rates were unrelated (unaltered) by the increase in light intensity at night. We suggest that ALAN is detrimental for the condition of the isopods, likely by reducing the activity and feeding of these nocturnal organisms, and that the isopods compensate this by absorbing nutrients more efficiently in order to maintain growth levels.
... Although an indispensable tool for human safety and function, nighttime artificial illumination is disruptive for many organisms, including humans, which have evolved under natural light-dark patterns (Ouyang, Davies, & Dominoni, 2018). Serious physiological effects have been identified across taxa, including disruption of circadian rhythm, immune function, reproductive physiology, and endocrine pathways (Bedrosian, Fonken, Walton, & Nelson, 2011;de Jong et al., 2016a;Dominoni, Quetting, & Partecke, 2013a;Gaston et al., 2013Gaston et al., , 2014Ouyang et al., 2017, Robert, Lesku, Partecke, & Chambers, 2015. Furthermore, there is evidence that, within species, effects of light at night differ depending on wavelength, i.e., blue light is more stimulatory for locomotor activity than red light for most taxa (Figueiro & Rea, 2010;Muheim, Bäckman, & andÅkesson, 2002;Ouyang et al., 2015). ...
... For birds in the 5000 K night-light treatment, nighttime activity patterns significantly differed from the 3000 K and control groups in both slope and intercept without changes in total locomotor activity. This pattern of activity difference is consistent with that of an experiment on dose-dependent light intensity levels on nighttime activity in freeliving great tits (Parus major;de Jong et al., 2016a). However, if we compare our activity results with the actograms presented by de Jong et al., ...
... Artificial light at night (ALAN) comprises of any source of anthropogenic illumination at night, both indoor and outdoor, which drives changes in the physiology and behavior of the urban wildlife [17][18][19][20][21][22]. Studies from Palearctic and Nearctic cities suggest that ALAN disrupts the daily rhythms in songbirds by altering the circadian rhythms of sleep and hormone production [19,[22][23][24][25]. In particular, ALAN generates similar light levels to those observed during natural twilight periods (i.e., transition between day and night when the sun drops under the horizon) altering the circadian rhythms as a consequence of twilight period extension [26]. ...
... First, some tropical birds can be sensitive to slight photoperiodic variations and use it to initiate reproductive activity [55,56], then Saffron Finches could detect variations in natural light and ALAN. Second, birds living in urban sites exposed to different levels of ALAN (0.05-6 lux) can wake up earlier and sleep less [20,24,58], meaning Saffron Finches could anticipate the onset of their daily activities by waking up earlier and then starting to sing. In fact, in the studied city Saffron Finches, as well as other common species such as the Vermilion Flycatcher (Pyrocephalus rubinus) and the Tropical Kingbird (Tyrannus melancholicus), there was evidence that showed nocturnal singing near to lamp posts (Marín-Gómez, pers. ...
Article
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Anthropogenic noise and artificial light at night (ALAN) can disrupt the morning singing routines of urban birds, however, its influence on tropical species remains poorly explored. Here, I assessed the association between light and noise pollution with the dawn chorus onset of the Saffron Finch (Sicalis flaveola) in a city in Colombia. I studied 32 sites comprised of different conditions of urban development based on built cover. I recorded the time of the first song of the Saffron Finch, the conspecific density and measured anthropogenic noise and ALAN using smartphone apps. The findings of this study show that Saffron Finches living in highly developed sites sang earlier at dawn than those occupying less urbanized sites. Unexpectedly, this timing difference was related to ALAN instead of anthropogenic noise, suggesting that light pollution could drive earlier dawn chorus in a tropical urban bird. Saffron Finches could take advantage of earlier singing for signaling territorial ownership among neighbors. Future studies need to assess the influence of ALAN on the dawn chorus timing of Neotropical urban birds.
... The costs and benefits of ALAN for organisms may vary over time as a result of behavior, developmental plasticity and evolution as well as their direct and indirect interactions with other species in the community affected by ALAN (e.g., Knop et al. 2017). Among the potential costs of ALAN are disrupted circadian rhythms (e.g., Dominoni 2015;de Jong et al. 2016); suppressed melatonin, which can decrease immune and anti-oxidant function (e.g., Durrant et al. 2015); increased risk of predation (Silva et al. 2017); and decreased or less effective sleep (e.g., Ouyang et al. 2017), which may have carry-over effects on daytime behavior (Kurvers et al. 2018). On the other hand, organisms may also benefit from ALAN through increased foraging opportunities (termed the "night-light niche"; Garber 1978) due to increased feeding times and increased abundance or concentration of prey attracted to lights, both in the night and day (e.g., Rydell 1992;Petren et al. 1993;Davies et al. 2012;Welbers et al. 2017). ...
... One clear cost of ALAN observed in our study was decreased locomotor endurance for brown anoles from ALAN plots. Circadian disruptions, including altered sleep, can lead to altered melatonin levels, changes in patterns of reproductive and foraging activity, and metabolic disruptions (Dominoni 2015;de Jong et al. 2016). Lower quality and duration of sleep is associated with lower endurance and performance in humans (Belenky et al. 2003;Oliver et al. 2009). ...
Article
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With urbanization expanding into natural areas, it is increasingly important to understand how species subject to human-induced habitat alteration respond to novel opportunities and stressors. A pervasive consequence of urbanization is artificial light at night (ALAN), which previous studies have found introduces both costs and benefits for vertebrates. This understanding, however, primarily reflects findings from laboratory-controlled experiments or comparisons of wild populations in areas with long-standing differences in ALAN regimes. Here, we investigated the short-term costs and benefits for Anolis lizards during the period of initial exposure to ALAN using realistic light levels for urban areas (mean ± SD = 87.9 ± 36.7 lx at a distance of 3 m). As compared to controls, we hypothesized that adding ALAN would result in behavioral and physiological changes over the short term for brown anoles and their arthropod prey. In contrast to predictions, ALAN did not increase arthropod abundance or extend anole activity into the night. Structural habitat and sleep site use changed little in response to ALAN, which exposed about one-third of sleeping anoles in ALAN plots to light at night due to our manipulation. However, this direct light exposure resulted in lizards being more easily roused from sleep compared to lizards sleeping in the dark in control plots or in shadows in ALAN plots. The apparent inability of some anoles to adjust their sleep sites to avoid ALAN exposure may have contributed to their increased responsiveness at night and decreased locomotor endurance in the day. Our study suggests brown anoles can experience higher short-term costs than benefits during initial exposure to ALAN.
... In addition, female blue tits (Cyanistes careuleus) breeding in close proximity of street lights laid eggs 1.5 days in advance of females breeding in dark areas (Kempenaers et al., 2010). Other field studies have shown that ALAN can extend foraging activity (Russ et al., 2015), advance dawn singing times (Kempenaers et al., 2010), and increase daily locomotor activity, with early onset and delayed offset activity time associated to ALAN exposure (Dominoni et al., 2013b;de Jong et al., 2016). Given that the majority of animals across the globe use photoperiod to time reproductive development in anticipation to the expected maxima for annual resource availability, the effects of ALAN exposure on reproduction are likely to be far-reaching (Bradshaw and Holzapfel, 2010;Helm et al., 2013). ...
Preprint
In the modern era of industrialization, illuminated nights have become a common defining feature of human-occupied environments, particularly cities. Artificial light at night (ALAN) imposes several known negative impacts on the neuroendocrine system, metabolism, and seasonal reproduction of species living in the wild. However, we know little about the impact of ALAN on populations of birds that either live year-round in the same location or move to different latitudes across seasons. To test whether ALAN has differing impact on reproductive timing of the bird populations that winter in sympatry but breed at different latitudes, we monitored sedentary and migratory male dark-eyed juncos that were or were not exposed to low intensity (~2.5 lux) ALAN. All groups were held in common conditions and day length was gradually increased to mimic natural day length changes (NDL). We assessed seasonal reproductive response from initiation to termination of the breeding cycle. As expected based on earlier research, the sedentary birds exhibited earlier gonadal recrudescence and terminated breeding later than the migratory birds. In addition, resident and migrant birds exposed to ALAN initiated gonadal recrudescence earlier and terminated reproduction sooner as compared to their conspecifics experiencing NDL. Importantly, the difference in the reproductive timing of sedentary and migratory populations was maintained even when exposed to ALAN. This variation in the seasonal reproductive timing may likely have a genetic ground or early developmental effects imposed due to different latitude of origin. This study reveals first that latitude-dependent variation in reproductive timing is maintained despite exposure to ALAN, and second that ALAN accelerated reproductive development across both migrants and residents. The results corroborating relationship between latitude, population, and ALAN impact on seasonal reproductive timing, may provide a potential mechanism to test the fitness of a population and its range expansion to exploit urban environment.
... They may also interfere with birds' circadian rhythms [93]. Artificial light pollution at night exerts a particularly adverse effect on passerine birds that migrate mainly at that time [92]. ...
Article
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This opinion piece highlights the role of migratory birds in the spread of ticks and their role in the circulation and dissemination of pathogens in Europe. Birds with different lifestyles, i.e., non-migrants residing in a specific area, or short-, medium-, and long-distance migrants, migrating within one or several distant geographical regions are carriers of a number of ticks and tick-borne pathogens. During seasonal migrations, birds that cover long distances over a short time and stay temporarily in different habitats can introduce tick and pathogen species in areas where they have never occurred. An increase in the geographical range of ticks as well as the global climate changes affecting the pathogens, vectors, and their hosts increase the incidence and the spread of emerging tick-borne diseases worldwide. Tick infestations of birds varied between regions depends on the rhythms of tick seasonal activity and the bird migration rhythms determined by for example, climatic and environmental factors. In areas north of latitude ca. 58°N, immature Ixodes ricinus ticks are collected from birds most frequently, whereas ticks from the Hyalomma marginatum group dominate in areas below 42°N. We concluded that the prognosis of hazards posed by tick-borne pathogens should take into account changes in the migration of birds, hosts of many epidemiologically important tick species.
... Similarly, establishing whether "supermoon" events disrupt the previously observed correlations between mean, minimum, and maximum daily heart rates would ascertain the functional significance of sleep interruption at the energetics level. The disruption to the typical circadian T ab rhythm in geese occurring in response to natural cycles of ambient light levels may offer insight into how animals are responding to artificial light (De Jong, et al., 2016). Prior studies have demonstrated suppression of rest-phase torpor in urban birds and mammals (Le Tallex et al., 2015) in response to artificial light, which assumingly must come at a metabolic cost (Guppy & Withers, 1999). ...
Article
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The position of the Moon in relation to the Earth and the Sun gives rise to several predictable cycles, and natural changes in nighttime light intensity are known to cause alterations to physiological processes and behaviors in many animals. The limited research undertaken to date on the physiological responses of animals to the lunar illumination has exclusively focused on the synodic lunar cycle (full moon to full moon, or moon phase) but the moon's orbit-its distance from the Earth-may also be relevant. Every month, the moon moves from apogee, its most distant point from Earth-and then to perigee, its closest point to Earth. Here, we studied wild barnacle geese (Branta leucopsis) to investigate the influence of multiple interacting lunar cycles on the physiology of diurnally active animals. Our study, which uses biologging technology to continually monitor body temperature and heart rate for an entire annual cycle, asks whether there is evidence for a physiological response to natural cycles in lunar brightness in wild birds, particularly "supermoon" phenomena, where perigee coincides with a full moon. There was a three-way interaction between lunar phase, lunar distance, and cloud cover as predictors of nighttime mean body temperature, such that body temperature was highest on clear nights when the full moon coincided with perigee moon. Our study is the first to report the physiological responses of wild birds to "supermoon" events; the wild geese responded to the combination of two independent lunar cycles, by significantly increasing their body temperature at night. That wild birds respond to natural fluctuations in nighttime ambient light levels support the documented responses of many species to anthropo-genic sources of artificial light, that birds seem unable to override. As most biological systems are arguably organized foremost by light, this suggests that any interactions between lunar cycles and local weather conditions could have significant impacts on the energy budgets of birds. K E Y W O R D S circadian, energy expenditure, lunar cycles, supermoon
... While the harmful effects of artificial light at nighttime (ALAN) are becoming clear, the attention given to light pollution in protected areas is increasing [11]. Researchers have amplified various effects of ALAN, finding that ALAN has biological consequences on fauna [12,13], such as birds [14][15][16], turtles [12,17,18], and insects [19]. For instance, Grenis and Murphy found that ALAN contributes to the loss of insect biomass by affecting the traits of plants [19]. ...
Article
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With the rapid urbanization process, the construction of lighting facilities is increasing, whereas artificial light at nighttime (ALAN) negatively affects organisms in protected areas and threatens ecosystems. Therefore, a deep research of ALAN within protected areas is significant for better preserving biodiversity by scientific ALAN management. Taking the ecological conservation redline (ECR) in Zhejiang Province as a case study, we consistently applied remotely sensed ALAN data from 2000 to 2020 for exploring spatiotemporal changing characteristics of ALAN. More importantly, both human living and ecological safety were considered to classify ALAN status in 2019 in order to propose rational suggestions for management. The results showed ALAN intensified and expanded, increasing from 3.05 × 1012 nW·sr−1 to 5.24 × 1013 nW·sr−1 at an average growth rate of 2.35 × 1012 nW·sr−1·year−1. Hotspot analysis and bivariate spatial clustering identified the aggregation situation of ALAN and the population. They showed that statistically significant ALAN hotspots accounted for only 20.40% of the study area while providing 51.82% of the total ALAN. Based on the mismatches between human demand and ALAN supply, two crucial areas were identified where regulation is needed most, and targeted policy recommendations were put forward. The study results can contribute to the effective regulation of ALAN in protected areas.
... Then, at the peak of species abundance, foraging activity and breeding periods strongly depend on seasons (e.g., Newson et al. 2015, Salvarina et al. 2018, Lučan and Radil 2010. That is why species are affected differently by artificial lighting, according to time of year, e.g., response of avian daily rhythms to light intensity (de Jong et al. 2016). Monthly and seasonal regimes of lunar sky brightness also shape biological timings and spatial repartition of species, e.g., for zooplankton's vertical migrations, and can be masked or even very negatively impacted by the skyglow generated by the extent of artificial lighting sources (Davies et al. 2013, Ludvigsen et al. 2018. ...
Article
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Artificial light at night (ALAN) is nowadays recognized as a major anthropogenic pressure on the environment on a global scale and as such is called light pollution. Through its attractive or deterrent effects, and its disruption of the biological clock for many animal and plant taxa, ALAN is increasingly recognized as a major threat to global biodiversity, which ultimately alters the amount, the quality, and the connectivity of available habitats for taxa. Biodiversity conservation tools should, therefore, include ALAN spatial and temporal effects. The ecological network, i.e., the physical and functional combination of natural elements that promote habitat connectivity, provides a valuable framework for that purpose. Understood as a social-ecological framework, it offers the opportunity to take into account the multiple uses of nocturnal spaces and times, by humans and nonhumans alike. Here we present the concept of "dark ecological network." We show this concept is able to grasp the effects of ALAN in terms of habitat disturbances and integrates temporal dimensions of ecological processes into biodiversity conservation planning. Moreover, it is also intended to trivialize the practices of darkness protection by turning them into the ordinary practices of land use planning. From an operational point of view, the challenge is to translate the levers for reducing ALAN-induced effects into a political method for its "territorialization." To achieve this objective, we propose a course of action that consists of building an interdisciplinary repertoire of contextualized knowledge (e.g., impacts on wildlife, human/lightscape relationship, existing legal tools, etc.), in order to deduce from it a number of practical supports for the governance of the dark ecological network in response to societal and ecological issues.
... MEL levels in our control groups were comparable to previously published data for this species [60]. In all groups that were exposed to ALAN, nocturnal MEL levels were lower compared to the controls that were exposed to dark nights, and this is in line with the MEL suppression previously observed by others in great tits [61], and in female zebra finches [6,7]. Under control (dark nights) conditions, females and males had similar MEL levels (417 ± 22 pg/mL and 407 ± 19.5 pg/mL, respectively; the females' concentration is calculated from the means of the control groups before ALAN exposure in [6,7], and the males' concentration is calculated from the respective means in the present study). ...
Article
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We recently reported that artificial light at night (ALAN), at ecologically relevant intensities (1.5, 5 lux), increases cell proliferation in the ventricular zone and recruitment of new neurons in several forebrain regions of female zebra finches (Taeniopygia guttata), along with a decrease of total neuronal densities in some of these regions (indicating possible neuronal death). In the present study, we exposed male zebra finches to the same ALAN intensities, treated them with 5′-bromo-2′-deoxyuridine, quantified cell proliferation and neuronal recruitment in several forebrain regions, and compared them to controls that were kept under dark nights. ALAN increased cell proliferation in the ventricular zone, similar to our previous findings in females. We also found, for the first time, that ALAN increased new neuronal recruitment in HVC and Area X, which are part of the song system in the brain and are male-specific. In other brain regions, such as the medial striatum, nidopallium caudale, and hippocampus, we recorded an increased neuronal recruitment only in the medial striatum (unlike our previous findings in females), and relative to the controls this increase was less prominent than in females. Moreover, the effect of ALAN duration on total neuronal densities in the studied regions varied between the sexes, supporting the suggestion that males are more resilient to ALAN than females. Suppression of nocturnal melatonin levels after ALAN exhibited a light intensity-dependent decrease in males in contrast to females, another indication that males might be less affected by ALAN. Taken together, our study emphasizes the importance of studying both sexes when considering ALAN effects on brain plasticity.
... The daily rhythm of melatonin production is of particular importance when studying the effects of light pollution by exposure to ALAN because the main production of melatonin occurs during the night and can be inhibited directly by the exposure to ALAN. The natural nocturnal melatonin production has been shown to be suppressed in invertebrates (e.g., Durrant et al., 2015, Jones et al., 2015 and vertebrates (e.g., Brüning et al., 2015, de Jong et al., 2016, Firth et al., 2006, Grubisic et al., 2019, Tapia-Osorio et al., 2013, Wright and Bruni, 2004. ALAN mainly derives from centers of human activities, namely cities, which typically occur close to water and especially close to bodies of freshwater (Kummu et al., 2011). ...
Thesis
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Künstliches Licht in der Nacht (ALAN) entsteht in Zentren menschlicher Aktivität und erhellt die Nacht, wodurch biologische Rhythmen von Menschen und Wildtieren gestört werden können. Skyglow ist eine diffuse Aufhellung des Nachthimmels aufgrund von Reflexion und Streuung von ALAN, welche indirekt große Bereiche (vor-)städtischer Ökosysteme beleuchtet. Da sich Zentren menschlicher Aktivität häufig in der Nähe von Flüssen und Seen befinden, kann sich Skyglow unverhältnismäßig stark auf wildlebende Tiere in Süßwassergebieten auswirken. In drei Experimenten wurden die Auswirkungen von ALAN auf die Physiologie des Europäischen Flussbarsches untersucht. Die Fische wurden verschiedenen Versuchsbedingungen ausgesetzt: 1) niedrige ALAN-Intensitäten von 0,01, 0,1 und 1 lx unter kontrollierten Bedingungen, 2) höhere ALAN-Intensitäten von 1, 10 und 100 lx unter kontrollierten Bedingungen und 3) eine niedrige ALAN-Intensität von 0,06 lx in einem Feldexperiment. In den vorgestellten Experimenten unterdrückten niedrige ALAN-Intensitäten den nächtlichen Melatoninspiegel sowie teilweise Reproduktionshormone bei Weibchen. Höhere ALAN-Intensitäten verringerten das aktivste Schilddrüsenhormon und das relative Lebergewicht der Fische. Diese Arbeit zeigt physiologische Veränderungen bereits bei schwachen ALAN-Intensitäten, wie sie in großen Bereichen (vor-)städtischer Ökosysteme in Form von Skyglow vorkommen. Die empfindlichste Reaktionsvariable auf die Belastung durch ALAN bei Fischen ist der nächtliche Melatoninspiegel. Mögliche Wirkungen von ALAN auf andere physiologische Parameter können durch direkten Lichteinfall oder indirekt über reduziertes Melatonin ausgelöst werden. Diese Arbeit trägt zum Verständnis der Schwellenwerte für verschiedene physiologische Effekte durch eine mehrwöchige ALAN-Exposition bei. Schwellenwerte für ALAN-Intensitäten könnten zukünftig notwendige Deskriptoren für die Ausarbeitung von regulierenden Maßnahmen zur Reduzierung von Lichtverschmutzung liefern.
... Among avian species, European blackbirds that experienced artificial light at night developed reproductively a month earlier than blackbirds not exposed to light, which may limit male reproductive success if they do not have access to breeding females (Dominoni et al., 2013). Great tits lost approximately 40 min of sleep when they were exposed to artificial light inside their nest boxes throughout the night (Raap et al., 2017), and the more intense the light was at night, the more active great tits were throughout the day and night (de Jong et al., 2016). Greater exposure to artificial light at night was associated with decreased nitric oxide levels and increased haptoglobin levels in free-living nestling great tits' blood (Raap et al., 2016). ...
Article
Popular evening events, such as Zoo Lights, increase the exposure of animals in managed care to stressors such as artificial light and noise, which may alter their behavior and negatively affect animal well-being. The pair of great Indian hornbills (Buceros bicornis) at Denver Zoo provided an opportunity to study the impacts of these stressors because their exhibit was open every evening during Zoo Lights 2017. We expected the hornbills to display increased aggressive behaviors during Zoo Lights due to more exposure to stressors compared to the periods before and after the holiday event. Alternatively, if behavioral changes were associated with hornbills' breeding season which runs from December-March, we expected the hornbills to engage in more affiliative behaviors, and to increase conspecific and nest proximity, during and after Zoo Lights compared to before it due to the onset and progression of the breeding season. The hornbills did not engage in significantly more aggressive behavior during Zoo Lights than before or after it. By contrast, the hornbills engaged in significantly more affiliative behaviors and increased conspecific proximity during and after Zoo Lights compared to before the event. These results are consistent with the timing of the hornbills' breeding season and not with the increased exposure to stressors during Zoo Lights. This case study provides an early step in assessing the impact of Zoo Lights on animals whose exhibits are part of these holiday events. Studies like this will help inform best practices for Zoo Lights events such that they are positive experiences for the zoo, visitors, and animals.
... Exposure to night-time light disrupts the circadian system and desynchronizes the associated behavioural rhythms in both wild and captive birds. In Eurasian Blackbird (Turdus merula) and Great Tits (Parus major), LAN induced activity in dark phase and nocturnal restlessness was observed [21,22]. Interestingly, the effects of ALAN on activity behaviour have been shown to be intensity and wavelength dependent in Great Tits [11]. ...
Article
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In recent times, there has been an unprecedented increase in usage of electrical lightning. This has led to increase in artificial light at night (ALAN), and it has been suggested as a source of environmental pollution. ALAN exposure has been reported to be associated with disruption of daily rhythms and serious health consequences, such as immune, metabolic, and cognitive dysfunctions in both birds and mammals. Given the worldwide pervasiveness of ALAN, this research topic is also important from an ecological perspective. In birds, daily timings and appropriate temporal niches are important for fitness and survival. Daily rhythms in a wide array of functions are regulated by the circadian clock(s) and endogenous oscillators present in the body. There is accumulating evidence that exposure to ALAN disrupts clock-regulated daily rhythms and suppresses melatonin and sleep in birds. Circadian clock, melatonin, and sleep regulate avian cognitive performance. However, there is limited research on this topic, and most of the insights on the adverse effects of ALAN on cognitive functions are from behavioural studies. Nevertheless, these results raise an intriguing question about the molecular underpinning of the ALAN-induced negative consequences on brain functions. Further research should be focused on the molecular links between ALAN and cognitive performance, including the role of melatonin, which could shed light on the mechanism by which ALAN exposures lead to negative consequences.
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The global catastrophe of natural biodiversity and ecosystem services are expedited with the growing human population. Repercussions of artificial light at night ALAN are much wider, as it varies from unicellular to higher organism. Subsequently, hastened pollution and over exploitation of natural resources accelerate the expeditious transformation of climatic phenomenon and further cause global biodiversity losses. Moreover, it has a crucial role in global biodiversity and ecosystem services losses via influencing the ecosystem biodiversity by modulating abundance, number and aggregation at every levels as from individual to biome levels. Along with these affects, it disturbs the population, genetics and landscape structures by interfering inter- and intra-species interactions and landscape formation processes. Furthermore, alterations in normal light/dark (diurnal) signalling disrupt the stable physiological, biochemical, and molecular processes and modulate the regulating, cultural and provisioning ecosystem services and ultimately disorganize the stable ecosystem structure and functions. Moreover, ALAN reshapes the abiotic component of the ecosystem, and as a key component of global warming via producing greenhouse gases via emitting light. By taking together the above facts, this review highlights the impact of ALAN on the ecosystem and its living and non-living components, emphasizing to the terrestrial and aquatic ecosystem. Further, we summarize the means of minimizing strategies of ALAN in the environment, which are very crucial to reduce the further spread of night light contamination in the environment and can be useful to minimize the drastic impacts on the ecosystem.
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Der hier vorgelegte Leitfaden zur Neugestaltung und Umrüstung von Beleuchtungsanlagen soll Entscheidungsträgerinnen und Entscheidungsträgern helfen, indem Vorgaben an die Beleuchtung im Außenraum konkretisiert und Maximalwerte definiert werden. Dadurch sollen nachteilige Auswirkungen durch Beleuchtungen auf Tiere, Pflanzen und ihre Lebensräume, sowie den Menschen vermieden bzw. minimiert werden. Zudem sollen Hinweise und Maßnahmen für eine nachhaltige, naturschutzfreundliche und effiziente öffentliche Beleuchtung aufgezeigt und damit der fortschreitenden Erhellung der Nachtlandschaften entgegengewirkt werden.
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We investigated whether nocturnal eating was causal to the impairment of metabolism and sleep disruption in diurnal animals exposed to illuminated nights. Adult zebra finches hatched and raised in 12 h light: 12 h darkness (LD) were exposed to 5-lux dim light at night (dLAN, two groups), with a control group maintained on LD. For the next 3 weeks, the food availability to one of the dLAN groups was restricted to the 12 h light period (dLAN -F); the other dLAN (dLAN +F) and LD groups were continued on ad lib feeding. In spite of similar food intakes, dLAN +F condition led to the fat accumulation and weight gain. These birds showed concurrent changes in hepatic expression of genes associated with carbohydrate and lipid metabolism, suggesting an enhanced gluconeogenesis and impaired fatty acids synthesis. Increased sirt1 mRNA levels indicated the activation of molecular mechanisms to counter-balance the metabolic damage under dLAN +F. Furthermore, reduced bout length and total duration of the nocturnal sleep suggested a poorer sleep in dLAN +F condition. Negative sleep effects of dLAN were supported by the lower hypothalamic expression of sleep promoting sik3 and camkii genes, and higher mRNA expression of awake promoting achm3 gene in dLAN +F, compared to the LD condition. Importantly, dLAN-induced negative effects in metabolism and sleep were alleviated in the dLAN –F group. These results suggest the role of timed feeding in alleviating the negative impact of illuminated nights in metabolism and sleep in diurnal zebra finches.
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Reproduction is a key biological function requiring a precise synchronization with annual and daily cues to cope with environmental fluctuations. Therefore, humans and animals have developed well-conserved photoneuroendocrine pathways to integrate and process circadian and seasonal light signals within the hypothalamic-pituitary-gonadal axis. However, in the past century, industrialization and the modern 24/7 human lifestyle have imposed detrimental changes in natural habitats and rhythms of life. Indeed, exposure to an excessive amount of artificial light at inappropriate timing because of shift work and nocturnal urban lighting, as well as the ubiquitous environmental contamination by endocrine-disrupting chemicals, threaten the integrity of the daily and seasonal timing of biological functions. Here we review recent epidemiological, field and experimental studies to discuss how light and chemical pollution of the environment can disrupt reproductive rhythms by interfering with the photoneuroendocrine timing system.
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Increased exposure to light pollution perturbs physiological processes through misalignment of daily rhythms at the cellular and tissue levels. Effects of artificial light-at-night (ALAN) on diel properties of immunity are currently unknown. We therefore tested the effects of ALAN on diel patterns of cytokine gene expression, as well as key hormones involved with the regulation of immunity, in zebra finches (Taeniopygia guttata). Circulating melatonin and corticosterone, and mRNA expression levels of pro- (IL-1β, IL-6) and anti-inflammatory (IL-10) cytokines were measured at six time points across 24-h day in brain (nidopallium, hippocampus, and hypothalamus) and peripheral tissues (liver, spleen, and fat) of zebra finches exposed to 12 h light:12 h darkness (LD), dim light-at-night (DLAN) or constant bright light (LLbright). Melatonin and corticosterone concentrations were significantly rhythmic under LD, but not under LLbright and DLAN. Genes coding for cytokines showed tissue-specific diurnal rhythms under LD and were lost with exposure to LLbright, except IL-6 in hypothalamus and liver. In comparison to LLbright, effects of DLAN were less adverse with persistence of some diurnal rhythms, albeit with significant waveform alterations. These results underscore the circadian regulation of biosynthesis of immune effectors and imply the susceptibility of daily immune and endocrine patterns to ALAN.
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Globally increasing levels of artificial light at night (ALAN) are associated with shifting rhythms of behaviour in many wild species. However, it is unclear whether changes in behavioural timing are paralleled by consistent shifts in the molecular clock and its associated physiological pathways. Inconsistent shifts between behavioural and molecular rhythms, and between different tissues and physiological systems, disrupt the circadian system, which coordinates all major body functions. We therefore compared behavioural, transcriptional and metabolomic responses of captive great tits (Parus major) to three ALAN intensities or to dark nights, recording activity and sampling brain, liver, spleen and blood at mid-day and midnight. ALAN advanced wake-up time, and this shift was paralleled by advanced expression of the clock gene BMAL1 in all tissues, suggesting close links between behaviour and clock gene expression across tissues. However, further analysis of gene expression and metabolites revealed that clock shifts were inconsistent across physiological systems. Untargeted metabolomic profiling showed that only 9.7% of the 755 analysed metabolites followed the behavioural shift. This high level of desynchronization indicates that ALAN disrupted the circadian system on a deep, easily overlooked level. Thus, circadian disruption could be a key mediator of health impacts of ALAN on wild animals.
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Ecological artificial light at night (ALAN) has been increasingly associated with negative effects on the behavior and ecology of wild birds. However, the impacts of short-term bright ALAN on the temporal biology of companion animals and the underlying mediating mechanism are unknown. We evaluated impacts of 1X60-min/middle night ALAN (200 lux, λDominant = 460 nm) nightly with or without melatonin administration on growth performance, reproductive capacity, food and water intake, and stress responses in Australian budgerigars (Melopsittacus undulatus) under captivity. 36 birds were housed in pairs under natural photoperiod and were equally divided into three groups: control, natural conditions; ALAN, control + ALAN; and melatonin, ALAN + melatonin in the drinking water during the dark period. Birds were regularly monitored for body mass, egg production, and hatchability over four months. Food intake, water consumption, and daily rhythm of fecal corticosterone were also evaluated. ALAN increased mass gain, food intake, water consumption, and drastically decreased reproductive capacity, whereas stress responses were markedly augmented. Melatonin restored food and water intake to control levels but partly reversed mass gain. Melatonin failed to ameliorate the impaired reproductive capacity despite reducing the stress responses to basal levels. These results suggest that the ALAN-induced negative impacts cannot be attributed solely to direct effects of melatonin suppression or/and exacerbated stress responses and the involvement of other photoperiodic pathway components warrant further studies. Finally, the results of our study may be of importance for improving the housing conditions of companion animals at least as concern bright ALAN exposures.
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The ecological impact of artificial light at night (ALAN) on phenological events such as reproductive timing is increasingly recognized. In birds, previous experiments under controlled conditions showed that ALAN strongly advances gonadal growth, but effects on egg‐laying date are less clear. In particular, effects of ALAN on timing of egg‐laying are found to be year‐dependent, suggesting an interaction with climatic conditions such as spring temperature, which is known have strong effects on the phenology of avian breeding. Thus, we hypothesized that ALAN and temperature interact to regulate timing of reproduction in wild birds. Field studies have suggested that sources of ALAN rich in short wavelengths can lead to stronger advances in egg‐laying date. We therefore tested this hypothesis in the great tit (Parus major), using a replicated experimental setup where eight previously unlit forest transects were illuminated with either white, green, or red LED light, or left dark as controls. We measured timing of egg‐laying for 619 breeding events spread over six consecutive years and obtained temperature data for all sites and years. We detected overall significantly earlier egg‐laying dates in the white and green light versus the dark treatment, and similar trends for red light. However, there was a strong inter‐annual variability in mean egg‐laying dates in all treatments, which was explained by spring temperature. We did not detect any fitness consequence of the changed timing of egg‐laying due to ALAN, which suggests that advancing reproduction in response to ALAN might be adaptive.
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Nighttime lighting is an increasingly important anthropogenic environmental stress on plants and animals. Exposure to unnatural lighting environments may disrupt circadian rhythm. However, studies involved in molecular biology, e.g. disruption of molecular circadian clock by light pollution, always have a small sample sizes. The small sample sizes result in a low statistical power and difficulties in replicating prior results. Here, a power-calibrated meta-analysis was developed to overcome these weakness. The results demonstrated that effect size of 2.48 in clock genes induced by artificial light would promised the reproducibility of the results as high as 80%. Long wavelength light entrained the positive core clock genes and negative core clock genes with robust circadian rhythmic expression, whereas some of those genes, e.g. cClock, cCry1, cCry2, cPer2, and cPer3, were arrhythmic in short wavelength light. Artificial light entrained the transcriptional-translational feedback loop of molecular clock in a wavelength-dependent manner. The expression positive core clock genes (cBmal1, cBmal2 and cClock), cAanat gene and melatonin were the greatest in short wavelength light and the lowest in long wavelength light. However, for negative regulators of molecular clock (cCry1, cCry2, cPer2 and cPer3), the greatest were in long wavelength light and the lowest were in short wavelength light. Our study opens up new opportunities to understand and strengthen conclusions based on the studies with small sample sizes and provides further insight about the disrupting in circadian rhythm by short wavelength light. Especially, the global lighting is shifting from “yellow” sodium lamps toward blue-enriched “white” light-emitting diodes (LEDs).
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Natural light cycles are being eroded over large areas of the globe by the direct emissions and sky brightening that result from sources of artificial night-time light. This is predicted to affect wild organisms, particularly because of the central role that light regimes play in determining the timing of biological activity. Although many empirical studies have reported such effects, these have focused on particular species or local communities and have thus been unable to provide a general evaluation of the overall frequency and strength of these impacts. Using a new database of published studies, we show that exposure to artificial light at night induces strong responses for physiological measures, daily activity patterns and life history traits. We found particularly strong responses with regards to hormone levels, the onset of daily activity in diurnal species and life history traits, such as the number of offspring, predation, cognition and seafinding (in turtles). So far, few studies have focused on the impact of artificial light at night on ecosystem functions. The breadth and often strength of biological impacts we reveal highlight the need for outdoor artificial night-time lighting to be limited to the places and forms—such as timing, intensity and spectrum—where it is genuinely required by the people using it to minimize ecological impacts.
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Global expansion of human activities is associated with the introduction of novel stimuli, such as anthropogenic noise, artificial lights and chemical agents. Progress in documenting the ecological effects of sensory pollutants is weakened by sparse knowledge of the mechanisms underlying these effects. This severely limits our capacity to devise mitigation measures. Here, we integrate knowledge of animal sensory ecology, physiology and life history to articulate three perceptual mechanisms—masking, distracting and misleading—that clearly explain how and why anthropogenic sensory pollutants impact organisms. We then link these three mechanisms to ecological consequences and discuss their implications for conservation. We argue that this framework can reveal the presence of ‘sensory danger zones’, hotspots of conservation concern where sensory pollutants overlap in space and time with an organism’s activity, and foster development of strategic interventions to mitigate the impact of sensory pollutants. Future research that applies this framework will provide critical insight to preserve the natural sensory world. Anthropogenic sensory pollutants, such as noise, light and chemicals, are affecting biodiversity. This Perspective uses an understanding of animal sensory ecology to explore how these impacts can be mitigated.
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The large-scale impact of urbanization on wildlife is rather well documented, however the mechanisms underlying the effects of urban environments on animal physiology and behaviour are still poorly understood. Here, we focused on one major urban pollutant - artificial light at night (ALAN) - and its effects on the capacity to mount an innate immune response in wild great tit Parus major nestlings. Exposure to ALAN alters circadian rhythms of physiological processes, by disrupting the nocturnal production of the hormone melatonin. Nestlings were exposed to a light source emitting 3 lux for seven consecutive nights. Subsequently, nestlings were immune-challenged with a lipopolysaccharide injection, and we measured haptoglobin and nitric oxide levels pre- and post-injection. Both haptoglobin and nitric oxide are important markers for innate immune function. We found that ALAN exposure altered the innate immune response, with ALAN nestlings having lower haptoglobin and higher nitric oxide levels after the immune-challenge compared to dark-night nestlings. Unexpectedly, nitric oxide levels were overall, lower after the immune-challenge than before. These effects were likely mediated by melatonin, since ALAN-treated birds had on average 49% lower melatonin levels than the dark-night birds. ALAN exposure did not have any clear effects on nestling growth. This study provides a potential physiological mechanism underlying the documented differences in immune function between urban and rural birds observed in other studies. Moreover, it gives evidence that ALAN exposure affects nestling physiology, potentially causing long-term effects on physiology and behaviour, which ultimately can affect their fitness.
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Light pollution is a widespread phenomenon with major consequences on nocturnal organisms from individual to community. However, its effects on diurnal organisms are still scarcely studied. We exposed diurnal parasitoid wasps (Venturia canescens) to low (0.7 lux) or high (20 lux) artificial light for two to eight consecutive nights, and quantified its consequences on their physiology and daytime behaviour compared to a control group (0 lux). We next considered potential trans‐generational effects on offspring whose mothers were exposed to light pollution. While in the dark night the wasps showed no activity, exposure to artificial light triggered nocturnal activity and altered diurnal behaviours related to foraging. Wasps exposed to light at night had a greater propensity to choose hosts rather than food compared to controls. They also spent more time feeding when exposed to 0.7 lux of light at night. However, these behavioural modifications were not related to changes in individual energy reserves. Light pollution effects persisted at trans‐generational level: offspring development time and latency before feeding increased when mothers were exposed to 0.7 lux light at night. Even at low intensity, light pollution alters foraging behaviour of a diurnal insect. Searching for hosts or food being essential for fitness, light pollution is likely to have long‐term repercussions on insect populations. Light pollution caused behavioural modifications potentially beneficial for V. canescens in the short term. However, longer term studies (e.g. on lifetime reproductive success) are needed to fully understand its consequences on insects
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Artificial light at night (ALAN) is closely associated with modern societies and is rapidly increasing worldwide. A dynamically growing body of literature shows that ALAN poses a serious threat to all levels of biodiversity - from genes to ecosystems. Many “unknowns” remain to be addressed however, before we fully understand the impact of ALAN on biodiversity and can design effective mitigation measures. Here, we distilled the findings of a workshop on the effects of ALAN on biodiversity at the first World Biodiversity Forum in Davos attended by several major research groups in the field from across the globe. We argue that 11 pressing research questions have to be answered to find ways to reduce the impact of ALAN on biodiversity. The questions address fundamental knowledge gaps, ranging from basic challenges on how to standardize light measurements, through the multi-level impacts on biodiversity, to opportunities and challenges for more sustainable use.
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Citation: Poblete, V.; Espejo, D.; Vargas, V.; Otondo, F.; Huijse, P. Characterization of Sonic Events Present in Natural-Urban Hybrid Habitats Using UMAP and SEDnet: The Case of the Urban Wetlands. Appl. Sci. 2021, 11, 8175. https://
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Artificial light is transforming the nighttime environment and quickly becoming one of the most pervasive pollutants on earth. Across taxa, light entrains endogenous circadian clocks that function to synchronize behavioral and physiological rhythms with natural photoperiod. Artificial light at night (ALAN) disrupts these photoperiodic cues and has consequences for humans and wildlife including sleep disruption, physiological stress and increased risk of cardiovascular disease. However, the mechanisms underlying organismal responses to dim ALAN, resembling light pollution, remain elusive. Light pollution exists in the environment at lower levels (<5 lux) than tested in many laboratory studies that link ALAN to circadian rhythm disruption. Few studies have linked dim ALAN to both the upstream regulators of circadian rhythms and downstream behavioral and physiological consequences. We exposed zebra finches (Taeniopygia gutatta) to dim ALAN (1.5 lux) and measured circadian expression of five pacemaker genes in central and peripheral tissues, plasma melatonin, locomotor activity, and biomarkers of cardiovascular health. ALAN caused an increase in nighttime activity and, for males, cardiac hypertrophy. Moreover, downstream effects were detectable after just short duration exposure (10 days) and at dim levels that mimic the intensity of environmental light pollution. However, ALAN did not affect circulating melatonin nor oscillations of circadian gene expression in the central clock (brain) or liver. These findings suggest that dim ALAN can alter behavior and physiology without strong shifts in the rhythmic expression of molecular circadian pacemakers. Approaches that focus on ecologically-relevant ALAN and link complex biological pathways are necessary to understand the mechanisms underlying vertebrate responses to light pollution.
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A most crucial feature of biological adaptation is the maintenance of a close temporal relationship of behaviour and physiology with prevailing 24-h light-dark environment, which is rapidly changing with increasing nighttime illumination. This study investigated developmental effects of the loss of night on circadian behaviour, metabolism and gene expressions in diurnal zebra finches born and raised under LL, with controls on 12 L:12D. Birds under LD were entrained, and showed normal body mass and a significant 24-h rhythm in both activity-rest pattern and mRNA expression of candidate genes that we measured. But, under LL, birds gained weight and accumulated lipid in the liver. Intriguingly, at the end of the experiment, the majority (4/5th) of birds under LL were rhythmic in activity despite arrhythmic expression in the hypothalamus of c-Fos (neuronal activity), Rhodopsin and Mel1-a genes (light perception), and clock genes (Bmal1, Per2 and Rev-erb β). In peripheral tissues, LL induced variable clock gene expressions. Whereas 24-h mRNA rhythm was abolished for Bmal1 in both liver and gut, it persisted for Per2 and Rev-erb β in liver, and for Per2 in gut. Further, we found under LL, the loss of 24-h rhythm in hepatic expression of Fasn and Cd36/Fat (biosynthesis and its uptake), and gut expression of Sglt1, Glut5, Cd36 and Pept1 (nutrient absorption) genes. As compared to LD, baseline mRNA levels of Fasn and Cd36 genes were attenuated under LL. Among major transporter genes, Sglt1 (glucose) and Cd36 (fat) genes were arrhythmic, while Glut5 (glucose) and Pept1 (protein) genes were rhythmic but with phase differences under LL, compared to LD. These results demonstrate dissociation of circadian behaviour from clock gene rhythms, and provide molecular insights into possible mechanisms at different levels (behaviour and physiology) that diurnal animals might employ in order to adapt to an emerging overly illuminated-night urban environment.
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Urbanization drives phenotypic variation in many animal species. This includes behavioral and physiological traits such as activity patterns, aggression, and hormone levels. A current challenge of urban evolutionary ecology is to understand the environmental drivers of phenotypic variation in cities. Moreover, do individuals develop tolerance to urban environmental factors, which underlie adaptative responses and contribute to the evolution of urban populations? Most available evidence comes from correlative studies and rare experiments where a single urban-related environmental factor has been manipulated in the field. Here we present the results of an experiment in which we tested for differences in the glucocorticoid (CORT) response of urban and rural blue tits nestlings (Cyanistes caeruleus) to artificial light at night (ALAN). ALAN has been suggested to alter CORT response in several animal species, but to date no study has investigated whether this effect of ALAN differs between urban and rural populations. Immediately after hatching, urban and forest broods were either exposed to 2 lux of ALAN (using an LED source mounted inside the nestbox) or received no treatment (dark control). The experiment lasted until the chicks fledged. When the chicks were 13 days old plasma samples were collected to measure baseline CORT concentrations, and feather samples to provide an integrative measure of CORT during growth. Forest birds had higher plasma CORT (pCORT) concentrations than their urban counterparts, irrespective of whether they were exposed to ALAN or not. Conversely, we found population-specific responses of feather CORT to ALAN. Specifically, urban birds that received ALAN had increased feather CORT compared with the urban dark controls, while the opposite was true for the forest birds. pCORT concentrations were negatively associated to fledging success, irrespective of population and treatment, while feather CORT was positively associated to fledging success in broods exposed to ALAN, but negatively in the dark control ones. Our results demonstrate that ALAN can play a role in determination of the glucocorticoid phenotype of wild animals, and may thus contribute to phenotypic differences between urban and rural animals.
Article
Photoperiod is a major factor regulating biological rhythms in animals and plants. At low latitudes, annual variation in daylength is low and species are expected to strongly rely on photic cues to reset their circadian clocks. A corollary is that individuals should be strongly affected by sudden changes in the photic regime as those generated by artificial light at night (ALAN). We tested this hypothesis in an anuran in Costa Rica (10°N). Using an outdoor experimental design, we exposed adult cane toads Rhinella marina, a broadly distributed tropical anuran species to two ALAN intensities (0.04 and 5 lx). Locomotor activity was reduced at the lowest intensity, and the activity pattern shifted from crepuscular to nocturnal. Contrary to humans and mice in which ALAN favor obesity, toads from the two exposed groups did not gain mass whereas controls did. Corticosterone was reduced at the highest intensity, a possible consequence of the reduced activity of toads or the altered regulation of their circadian pattern. Thus, the behavioral and physiological disruption that we observed supports the hypothesis of the strong reliance on photic cues to regulate circadian rhythms and control homeostasis in this intertropical anuran. Furthermore, our results suggest that the negative effects of ALAN on physiology, in particular body mass regulation, may differ between vertebrate groups, thus preventing anticipated generalization before more comparative studies have been carried out. We stress the importance of considering the impact of the changing nocturnal environment in the intertropical zone which host the largest fraction of biodiversity.
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In the modern era of industrialization, illuminated nights have become a common defining feature of human-occupied environments, particularly cities. Artificial light at night (ALAN) imposes several known negative impacts on the neuroendocrine system, metabolism, and seasonal reproduction of species living in the wild. However, we know little about the impact of ALAN on populations of birds that either live year-round in the same location or move to different latitudes across seasons. To test whether ALAN has a differing impact on the reproductive timing of bird populations that winter in sympatry but breed at different latitudes, we monitored sedentary and migratory male dark-eyed juncos that were or were not exposed to low intensity (∼2.5 ± 0.5 lux) ALAN. All groups were held in common conditions and day length was gradually increased to mimic natural day length changes (NDL). We assessed seasonal reproductive response from initiation to termination of the breeding cycle. As expected based on earlier research, the sedentary birds exhibited earlier gonadal recrudescence and terminated breeding later than the migratory birds. In addition, resident and migrant birds exposed to ALAN initiated gonadal recrudescence earlier and terminated reproductive events sooner as compared to their conspecifics experiencing NDL. Importantly, the difference in the reproductive timing of sedentary and migratory populations was maintained even when exposed to ALAN. This variation in the seasonal reproductive timing may likely have a genetic basis or be the result of early developmental effects imposed due to different light regimes related to the latitude of origin. This study reveals first that ALAN accelerated reproductive development across both migrants and residents and second that latitude-dependent variation in reproductive timing is maintained despite exposure to ALAN. These results corroborate a relationship between latitude, population, and reproductive timing while also revealing ALAN’s impact on seasonal reproductive timing. This study reveals that, ALAN accelerated reproductive development but maintained latitude-dependent variation in reproductive timing across both migrant and resident bird populations.
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Artificial lighting can alter individual behaviour, with often drastic and potentially negative effects on biological rhythms, daily activity and reproduction. Whether this is caused by a disruption of sleep, an important widespread behaviour enabling animals to recover from daily stress, is unclear. We tested the hypothesis that light pollution disrupts sleep by recording individual sleep behaviour of great tits, Parus major, that were roosting in dark nest-boxes and were exposed to light-emitting diode light the following night. Their behaviour was compared to that of control birds sleeping in dark nest-boxes on both nights. Artificial lighting caused experimental birds to wake up earlier, sleep less (–5%) and spent less time in the nest-box as they left their nest-box earlier in the morning. Experimental birds did not enter the nest-box or fall asleep later than controls. Although individuals in lit nest-boxes did not wake up more often nor decreased the length of their sleep bouts, females spent a greater proportion of the night awake. Our study provides the first direct proof that light pollution has a significant impact on sleep in free-living animals, in particular in the morning, and highlights a mechanism for potential effects of light pollution on fitness.
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Artificial light at night is one of the most apparent environmental changes accompanying anthropogenic habitat change. The global increase in light pollution poses new challenges to wild species, but we still have limited understanding of the temporal and spatial pattern of exposure to light at night. In particular, it has been suggested by several studies that animals exposed to light pollution, such as songbirds, perceive a longer daylength compared with conspecifics living in natural darker areas, but direct tests of such a hypothesis are still lacking. Here, we use a combination of light loggers deployed on individual European blackbirds, as well as automated radio-telemetry, to examine whether urban birds are exposed to a longer daylength than forest counterparts. We first used activity data from forest birds to determine the level of light intensity which defines the onset and offset of daily activity in rural areas. We then used this value as threshold to calculate the subjective perceived daylength of both forest and urban blackbirds. In March, when reproductive growth occurs, urban birds were exposed on average to a 49-min longer subjective perceived daylength than forest ones, which corresponds to a 19-day difference in photoperiod at this time of the year. In the field, urban blackbirds reached reproductive maturity 19 day earlier than rural birds, suggesting that light pollution could be responsible of most of the variation in reproductive timing found between urban and rural dwellers. We conclude that light at night is the most relevant change in ambient light affecting biological rhythms in avian urban-dwellers, most likely via a modification of the perceived photoperiod. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Article
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Daily, lunar and seasonal cycles of natural light have been key forms of environmental variation across the Earth’s surface since the first emergence of life. They have driven the development of biological phenomena from the molecule to the ecosystem, including metabolic and physiological pathways, the behaviour of individuals, geographical patterns of adaptation and species richness, and ecosystem cycles (e.g. [1–4]). Indeed, biological systems are arguably organized foremost by light [5–7]. The natural patterns of light have over the last 100 years come to be greatly disrupted through the introduction of artificial light into the night-time environment: artificial light at night (ALAN). This derives from a diversity of sources, including street lighting, advertising lighting, architectural lighting, security lighting, domestic lighting and vehicle lighting. ALAN disrupts natural patterns of light both via direct effects of illumination from these sources as well as via skyglow (the scattering by atmospheric molecules or aerosols in the atmosphere of ALAN that is emitted or reflected upwards; [8–10]).
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Artificial night-time illumination of natural habitats has increased dramatically over the past few decades. Generally, studies that assess the impact of artificial light on various species in the wild make use of existing illumination and are therefore correlative. Moreover, studies mostly focus on short-term consequences at the individual level, rather than long-term consequences at the population and community level-thereby ignoring possible unknown cascading effects in ecosystems. The recent change to LED lighting has opened up the exciting possibility to use light with a custom spectral composition, thereby potentially reducing the negative impact of artificial light. We describe here a large-scale, ecosystem-wide study where we experimentally illuminate forest-edge habitat with different spectral composition, replicated eight times. Monitoring of species is being performed according to rigid protocols, in part using a citizen-science-based approach, and automated where possible. Simultaneously, we specifically look at alterations in behaviour, such as changes in activity, and daily and seasonal timing. In our set-up, we have so far observed that experimental lights facilitate foraging activity of pipistrelle bats, suppress activity of wood mice and have effects on birds at the community level, which vary with spectral composition. Thus far, we have not observed effects on moth populations, but these and many other effects may surface only after a longer period of time. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
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The effects of artificial night lighting on animal behaviour and fitness are largely unknown. Most studies report short-term consequences in locations that are also exposed to other anthropogenic disturbance. We know little about how the effects of nocturnal illumination vary with different light colour compositions. This is increasingly relevant as the use of LED lights becomes more common, and LED light colour composition can be easily adjusted. We experimentally illuminated previously dark natural habitat with white, green and red light, and measured the effects on life-history decisions and fitness in two free-living songbird species, the great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) in two consecutive years. In 2013, but not in 2014, we found an effect of light treatment on lay date, and of the interaction of treatment and distance to the nearest lamp post on chick mass in great tits but not in pied flycatchers. We did not find an effect in either species of light treatment on breeding densities, clutch size, probability of brood failure, number of fledglings and adult survival. The finding that light colour may have differential effects opens up the possibility to mitigate negative ecological effects of nocturnal illumination by using different light spectra. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
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Artificial night lighting is expanding globally, but its ecological consequences remain little understood. Animals often use changes in day length as a cue to time seasonal behaviour. Artificial night lighting may influence the perception of day length, and may thus affect both circadian and circannual rhythms. Over a 3.5 month period, from winter to breeding, we recorded daily singing activity of six common songbird species in 12 woodland sites, half of which were affected by street lighting. We previously reported on analyses suggesting that artificial night lighting affects the daily timing of singing in five species. The main aim of this study was to investigate whether the presence of artificial night lighting is also associated with the seasonal occurrence of dawn and dusk singing. We found that in four species dawn and dusk singing developed earlier in the year at sites exposed to light pollution. We also examined the effects of weather conditions and found that rain and low temperatures negatively affected the occurrence of dawn and dusk singing. Our results support the hypothesis that artificial night lighting alters natural seasonal rhythms, independently of other effects of urbanization. The fitness consequences of the observed changes in seasonal timing of behaviour remain unknown.
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In passerine birds, the periodic secretion of melatonin by the pineal organ represents an important component of the pacemaker that controls overt circadian functions. The daily phase of low melatonin secretion generally coincides with the phase of intense activity, but the precise relationship between the melatonin and the behavioral rhythms has not been studied. Therefore, we investigated in European starlings (Sturnus vulgaris) (1) the temporal relationship between the circadian plasma melatonin rhythm and the rhythms in locomotor activity and feeding; (2) the persistence of the melatonin rhythm in constant conditions; and (3) the effects of light intensity on synchronized and free-running melatonin and behavioral rhythms. There was a marked rhythm in plasma melatonin with high levels at night and/or the inactive phase of the behavioral cycles in almost all birds. Like the behavioral rhythms, the melatonin rhythm persisted for at least 50 days in constant dim light. In the synchronized state, higher day-time light intensity resulted in more tightly synchronized rhythms and a delayed melatonin peak. While all three rhythms usually assumed a rather constant phase relationship to each other, in one bird the two behavioral rhythms dissociated from each other. In this case, the melatonin rhythm retained the appropriate phase relationship with the feeding rhythm.
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This review examines how birds use the annual cycle in photoperiod to ensure that seasonal events--breeding, molt, and song production--happen at the appropriate time of year. Differences in breeding strategies between birds and mammals reflect basic differences in biology. Avian breeding seasons tend to be of shorter duration and more asymmetric with respect to changes in photoperiod. Breeding seasons can occur at the same time each year (predictable) or at different times (opportunistic), depending on the food resource. In all cases, there is evidence for involvement of photoperiodic control, nonphotoperiodic control, and endogenous circannual rhythmicity. In predictable breeders (most nontropical species), photoperiod is the predominant proximate factor. Increasing photoperiods of spring stimulate secretion of gonadotropin-releasing hormone (GnRH) and consequent gonadal maturation. However, breeding ends before the return of short photoperiods. This is the consequence of a second effect of long photoperiods--the induction of photorefractoriness. This dual role of long photoperiods is required to impart the asymmetry in breeding seasons. Typically, gonadal regression through photorefractoriness is associated with a massive decrease in hypothalamic GnRH, essentially a reversal to a pre-pubertal condition. Although breeding seasons are primarily determined by photoperiodic control of GnRH neurons, prolactin may be important in determining the exact timing of gonadal regression. In tropical and opportunistic breeders, endogenous circannual rhythmicity may be more important. In such species, the reproductive system remains in a state of "readiness to breed" for a large part of the year, with nonphotic cues acting as proximate cues to time breeding. Circannual rhythmicity may result from a temporal sequence of different physiological states rather than a molecular or cellular mechanism as in circadian rhythmicity. Avian homologues of mammalian clock genes Per2, Per3, Clock, bmal1, and MOP4 have been cloned. At the molecular level, avian circadian clocks appear to function in a similar manner to those of mammals. Photoperiodic time measurement involves interaction between a circadian rhythm of photoinducibility and, unlike mammals, deep brain photoreceptors. The exact location of these remains unclear. Although the eyes and pineal generate a daily cycle in melatonin, this photoperiodic signal is not used to time seasonal breeding. Instead, photoperiodic responses appear to involve direct interaction between photoreceptors and GnRH neurons. Thyroid hormones are required in some way for this system to function. In addition to gonadal function, song production is also affected by photoperiod. Several of the nuclei involved in the song system show seasonal changes in volume, greater in spring than in the fall. The increase in volume is, in part, due to an increase in cell number as a result of neurogenesis. There is no seasonal change in the birth of neurons but rather in their survival. Testosterone and melatonin appear to work antagonistically in regulating volume.