Light pollution and habitat fragmentation in the grey mouse lemur

Light pollution and habitat fragmentation in the grey mouse lemur | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Light pollution and habitat fragmentation in the grey mouse lemur Thomas Le Tallec, Clara Hozer, Martine Perret, Marc Théry This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3220013/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Jan, 2024 Read the published version in Scientific Reports → Version 1 posted 8 You are reading this latest preprint version Abstract Light pollution, by changing organisms’ behavior, affects locomotion, migration and can ultimately fragment the habitat. To investigate the effects of light pollution on habitat fragmentation, we conducted an experimental study on a nocturnal and photosensitive primate, the grey mouse lemur ( Microcebus murinus ). Twelve males were housed individually in an apparatus with two cages connected by two corridors, opaque and transparent. During 4 nights, the transparent corridor was illuminated by specific light intensities: 0 lux, 0.3 lux, 20 lux and 51.5 lux corresponding respectively to total darkness, full moon, minimal intensity recommended by the European standard EN-13201 on public lighting, and to light pollution recorded in an urban area. Each night, general activity, use of corridors and cage occupancy were recorded using an infrared camera. For the first time in a nocturnal primate, results demonstrate that light pollution changes the preference of use of corridors, modifies the locomotor pattern and limits the ability of animals to efficiently exploit their environment according to a light intensity-dependent relationship. However, results indicate that a dark corridor allows partial compensation partly preserving general activities. This study highlights the necessity to consider light pollution during the implementation of conservation plans and the relevance of nocturnal frames. Biological sciences/Ecology/Behavioural ecology Biological sciences/Ecology/Conservation Biological sciences/Ecology/Urban ecology Biological sciences/Zoology/Animal behaviour artificial light corridor habitat fragmentation light pollution mammal Microcebus murinus mouse lemur Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Habitat fragmentation, which is one major factor implicated in the global decline of populations and species 1–3 , refers to the process of subdividing a continuous habitat into smaller discontinuous patches 4 . Specifically, habitat fragmentation simultaneously involves four processes: 1) reduction in habitat amount; 2) increase in number of habitat patches; 3) decrease in size of patches; 4) increase in isolation of patches 5 . In turn, these processes affect abiotic and biotic habitat conditions and, consequently, modify ecosystem equilibrium. Depending on species, these changes can have either positive or negative consequences on survival and fitness 6–8 . Over the past decades, extensive research has investigated habitat fragmentation related mechanisms 9–14 but only few studies have taken into account the introduction of artificial light in the nocturnal environment and its potential consequences on habitat fragmentation (Challéat et al., 2021; Laforge et al., 2019; Schirmer et al., 2019; Eisenbeis, 2006). However, light pollution has demonstrable effects on organisms’ behaviour, such as changes in orientation or attraction exerted by the illuminated environment, the ‘flight-to-light’ behaviour of nocturnal insects and migratory birds around artificial light being the best documented effect 18,19 . As a result, these behavioral disturbances can affect locomotion and migration patterns 20 and contribute to habitat fragmentation. There are two scenarios identified in which light pollution limits locomotion and migration: 1) the ‘captivity’ effect when organisms are disturbed from their normal activity by contact with artificial light and are unable to escape from the proximity of lighting, and 2) the ‘crash barrier’ effect when organisms are disturbed during long-distance movement by artificial light encountered in their travel path. Artificial light prevents organisms from following their original flyway and makes them unable to leave the illuminated environment. In mammals, few studies have documented habitat fragmentation through the effects of light pollution, whereas it is thought that mammals could be, along with birds, more behaviourally affected by artificial light because of the physical structure of their eye 21 . In a study of dispersing puma ( Puma concolor ), artificial light was detrimental for juveniles exploring new habitat, as they moved away from the urban artificial lights and navigated toward the darkest horizon, especially in a road undercrossing or in open habitats 22 . In bats, light pollution fragmented commuting routes with associated negative conservation consequences 23,24 . Specifically, slower-flying bats ( Rhinolophus hipposideros and Myotis spp.) avoided artificial light due to light-dependent predation risk. Similarly, another study highlighted that nighttime artificial illumination reduced total home size and home range overlap between conspecifics of two mammal species, the bank vole ( Myodes glareolus ) and the striped field mouse ( Apodemus agrarius ) 25 . In a study assessing the effect of artificial light on wildlife use of a passage structure submitted to different light treatments, the authors demonstrated that several mammal species, such as the columbia black-tailed deer ( Odocoileus hemionus columbianus ), the deer mouse ( Peromyscus maniculatus ) or the opossum ( Didelphis virginiana ) traversed a bridge under-road passage much less when sections or neighboring sections were lit compared to when none were, suggesting avoidance due to direct or nearby presence of artificial light 26 . These studies point out that light pollution, by changing movement patterns and interindividual interactions, establishes barriers to connectivity on the landscape and can isolate populations. This can result in reducing mammals’ ability to maintain genetic diversity, increasing their susceptibility to disturbance and disease, and limiting their access to resources, potentially leading to fitness consequences on the population level. These studies also highlight the need of finding mitigation solution of artificial light at night, such as under-road unlit corridors, and to examine their efficiency. To explore the effects of light pollution on locomotion in mammals and to extend the knowledge on habitat fragmentation, we conducted an experimental study on male grey mouse lemurs ( Microcebus murinus ). The grey mouse lemur, a Malagasy primate, is a convenient model to study the impact of light pollution because of the strong dependence of its behaviours, biological rhythms and physiological functions on photoperiod in the wild and in captivity and of the strong inhibitory effect of light on its general activity 27–29 . In this study, we investigated the effect of light pollution on behavioural activities of male mouse lemurs by testing the choice for travelling between a non-illuminated corridor and a corridor illuminated by different light intensities, increasing from full moon to streetlight (from 0.3 lux to 51.5 lux). In this photophobic and nocturnal mammal, we predict that male mouse lemurs will prefer the use of the non-illuminated corridor and this preference will increase according to a light intensity-dependent relationship. METHODS Animals We included 12 adult male grey mouse lemurs (35.5 ± 3.0 months) in this study, all in active sexual state. In captivity, seasonal variations of behaviours, daily rhythms and physiological functions are entrained by alternating 6-months periods of winter-like short-days photoperiod (SD; light/dark 10:14) and summer-like long-days photoperiod (LD; light/dark 14:10) under artificial light. Mouse lemurs were studied during 4 consecutive nights in mid-summer. They were housed individually at constant ambient temperature (24–26°C) and relative humidity (55%) with food in excess including a homemade milky mixture (46 kJ/day) and fresh fruits (18.5 kJ/day) delivered every day during the diurnal resting phase and water available ad libitum . Ethical Note All experiments were performed in the laboratory breeding-colony of Brunoy (UMR 7179 CNRS/MNHN, France; agreement n° E91-114-1 from the Direction Départementale de la Protection des Populations de l’Essonne) under the authorization n° Ce5/2011/067 from the Charles Darwin Ethics Committee in Animal Experiment and the Internal Review Board of the UMR 7179. All experiments were conducted under personal license to T. Le Tallec (authorization n° A91-621 from the Direction Départementale de la Protection des Populations de l’Essonne) and followed guidelines approved by the Association for the Study of Animal Behaviour and by the Animal Behavior Society 30 . The study is reported in accordance with ARRIVE guidelines (to reduce the number of animals involved in the experiment, animals were used as their own control, outcome measures are clearly defined, statistical analysis is fully detailed and the code is available on the following Figshare repository: [ https://doi.org/10.6084/m9.figshare.24047478 ], the species, sex and age of animals are reported, the experimental procedures are described in detail). Apparatus Animals were housed individually in an apparatus consisting of two cages (50×50×50 cm) connected by two Plexiglas® tubes (respectively opaque and transparent; length: 50 cm; diameter: 8 cm). Cage 1 was enriched with two tree branches and a nest box. Cage 2 was enriched with two tree branches and a feeder. The black opaque tube did not allow the transmission of any light. The transparent tube allowed the transmission of 92% of external light. Consequently, to feed after leaving the nesting box in cage 1, animals needed to cross one of the two tubes to reach cage 2. To rest and leave from cage 2, animals needed to cross again one of the two tubes to return to cage 1 (Fig. 1 ). Experimental protocol During 4 nights, the transparent tube was illuminated by four yellow LEDs (model L-1503YD, Kingbright, Taipei, Taiwan) regularly distributed every 12.5 cm (Fig. 1 ). LEDs simulated the irradiance spectra of streetlights with high pressure sodium lamps, the most common artificial light used for outdoor lighting characterized by emission lines from 569 to 616 nm 31 . Night 0 was a habituation period without any light treatment. Each following night, the transparent tube received a different illumination treatment with a specific light intensity: 1) 0 nmol photons.s − 1 .m − 2 in night 1 (control treatment, CTL); 2) 3.5 ± 0.1 nmol photons.s − 1 .m − 2 in night 2 (0.3 lux treatment), corresponding to the intensity of full moon 32 , the most important source of natural light at night 33 ; 3) 246.3 ± 0.9 nmol photons.s − 1 .m − 2 in night 3 (20 lux treatment), corresponding to the minimal light intensity to maintain in urban areas as recommended by the European standard EN-13201-02 on public lighting 34 ; 4) 628.0 ± 2.1 nmol photons.s − 1 .m − 2 in night 4 (51.5 lux treatment), corresponding to the average light intensity of streetlights with high pressure sodium lamps sampled in the city (77 lamps). For each LED, the average light intensity was calibrated before the experiment using a JAZ spectrometer (Ocean Optics, Dunedin, Florida, USA) between 300–700 nm. Before the experiment, we randomly determined the initial position of each tube (black or transparent) that was reversed between each light treatment, to prevent any laterality effect. In addition, before the experiment and between each light treatment, both tubes were cleaned to remove any olfactory cues. Daytime light was provided by fluorescent lamps (1 000 lux), placed in the ceiling of the experimental room. Throughout the experiment, the activity of each animal was filmed all night (10 hours) using an infrared camera (Handycam HDR-SR7, Sony, Tokyo, Japan) placed above the apparatus. We then determined for each light treatment the total number of crossings of both tubes. In addition, we determined for the black tube and the transparent tube separately the respective number of crossings (Nb and Nt) and the speed of crossing (Sb and St in cm.s − 1 ). The animal was considered to be in a tube when its four paws were seen in it. We also determined for each light treatment the proportion of time spent in each cage. The animal was considered to be in a cage when its four paws were seen in it. Before the experiment, values of body mass were controlled to ensure of their homogeneity (76.8 ± 2.9 g). Daily caloric food intake (CI in kJ) was calculated each day for each animal from the difference between provided and remaining food mass corrected for dehydration. Statistical Analysis All analyses were performed with R version 2.14.2 (R Development Core Team, 2001). We performed two mixed linear models (LMMs) using the ‘lmer’ function of the ‘lme4’ package with individuals’ identity as random variable to assess the effects of light treatment (CTL, 0.3 lux, 20 lux or 51.5 lux), tube (transparent or black) and the interaction between light treatment and tube on the number of crossings and on the mean speed of crossing. We further checked the distribution of residuals with ‘qqPlot’ function of the ‘car’ package for LMMs, and with Shapiro tests. The residuals did not comply with normality in the mean speed model, so we used the ‘boxcox’ function of the ‘MASS’ package to estimate an optimal power transformation that maximizes the normality of the transformed variable. Subsequently, we reran the model by applying the power transformation of -1.5 to the mean speed variable. We then ran post-hoc tests using the function ‘emmeans’ of the ‘emmeans’ package with the Tukey correction, in order to determine which specific groups differed from each other. We ran another LMM with individuals’ identity as random variable to assess the effect of light treatment on the proportion of occupancy of cage 2. Finally, we ran a generalized LMM with individuals’ identity as random variable and a poisson error structure to assess the effect of light treatment on the caloric intake. The probability level for statistical significance was p < 0.05. All values are presented as means ± standard error of the means. RESULTS Number of crossings and speed of crossing We observed a significant effect of the light treatment on the total number of tubes crossings (LMM: χ²=40.94, df = 3, p < 0.001). The total number of tubes crossings was not significantly different between the CTL and the 0.3 lux treatment (post-hoc test: t 77 = -0.39, p = 0.98, Fig. 2 A), nor between the 0.3 lux and the 20 lux treatments (post-hoc test: t 77 = 2.40, p = 0.09, Fig. 2 A), but was significantly reduced during the 20 lux and 51.5 lux treatments compared to the CTL treatment (respectively post-hoc tests: CTL-20 lux: t 77 = -2.79, p = 0.03 and CTL-51.5 lux: t 77 = -5.67, p < 0.001; Fig. 2 A), and was significantly reduced during the 51.5 lux treatment compared to the 0.3 and 20 lux treatments (respective post-hoc tests: 0.3lux-51.5 lux: t 77 = 5.27, p < 0.001 and 20 lux-51.5 lux: t 77 = 2.88, p = 0.03, Fig. 2 A). We also observed a significantly higher total number of crossings in the black tube than in the transparent tube (LMM: χ²=207.06, df = 1, p < 0.001), as well as a significant interaction between the tube and the light treatment on the number of crossings (LMM: χ²=209.53, df = 3, p < 0.001). While the number of crossings in the black tube was not different between the CTL, 0.3 lux and 20 lux treatments but significantly higher in the 51.5 lux treatment compared to the CTL and 0.3 lux treatments (respective post-hoc tests: CTL-0.3 lux: t 77 = 0.26, p = 1.00; CTL-20 lux: t 77 = 2.16, p = 0.38; CTL-51.5 lux: t 77 = 5.06, p < 0.001; 0.3 lux-20 lux: t 77 =-1.90, p = 0.55; 0.3 lux-51.5 lux: t 77 =-4.80, p < 0.001; 20 lux-51.5 lux: t 77 =-2.90, p = 0.09, Fig. 2 B), the number of crossings the transparent tube significantly decreased in the 20 lux and 51.5 lux treatments compared to the CTL and the 0.3 lux treatments (respective post-hoc tests: CTL-0.3 lux: t 77 =-0.82, p = 0.99; CTL-20 lux: t 77 =-6.11, p < 0.001; CTL-51.5 lux: t 77 =-13.07, p < 0.001; 0.3 lux-20 lux: t 77 = 5.29, p < 0.001; 0.3 lux-51.5 lux: t 77 = 12.25, p < 0.001; 20 lux-51.5 lux: t 77 = 6.96, p < 0.001, Fig. 2 B), but not between the CTL and the 0.3 lux treatments (t 77 =-0.82, p = 0.99, Fig. 2 B). Finally, the number of crossings the black tube was significantly higher than the transparent tube in the 20 lux and 51.5 lux treatment (respective post-hoc tests: 20 lux: t77 = 8.60, p < 0.001 and 51.5 lux: t 77 = 18.46, p < 0.001, Fig. 2 B) but not in the CTL and 0.3 lux treatments (respective post-hoc tests: CTL: t 77 = 0.32, p = 1; 0.3 lux: t 77 = 1.40, p = 0.85, Fig. 2 B). We observed a significant higher mean speed in the transparent tube than in the black tube (LMM: χ²=154.12, df = 1, p < 0.001), as well as a significant interaction between the tube and the light treatment on the mean speed (LMM: χ²=99.50, df = 3, p < 0.001). While the mean speed in the black tube was not different between the different treatments (respective post-hoc tests: CTL-0.3 lux: t 77 = 0.31, p = 1; CTL-20 lux: t 77 = 0.95, p = 0.98; CTL-51.5 lux: t 77 = 0.85, p = 0.99; 0.3 lux-20 lux: t 77 =-0.64, p = 1; 0.3 lux-51.5 lux: t 77 =-0.54, p = 1; 20 lux-51.5 lux: t 77 = 0.10, p = 1, Fig. 3 ), the mean speed in the transparent tube was significantly higher in the 20 lux and 51.5 lux treatments compared to the CTL and the 0.3 lux treatments (respective post-hoc tests: CTL-20 lux: t 77 = 12.38, p < 0.001; CTL-51.5 lux: t 77 = 25.22 p < 0.001; 0.3 lux-20 lux: t 77 =-10.31, p < 0.001; 0.3 lux-51.5 lux: t 77 =-23.15, p < 0.001, Fig. 3 ), as well as in the 51.5 lux treatment compared to the 20 lux treatment (20 lux-51.5 lux: t 77 =-12.84, p < 0.001, Fig. 3 ), but not between the CTL and the 0.3 lux treatments (t 77 = 2.07, p = 0.44, Fig. 3 ). Finally, the mean speed in the transparent tube was significantly higher than in the black tube in the 20 lux and 51.5 lux treatment (respective post-hoc tests: 20 lux: t 77 =-11.72, p < 0.001 and 51.5 lux: t 77 =-24.66, p < 0.001, Fig. 3 ) but not in the CTL and 0.3 lux treatments (respective post-hoc tests: CTL: t 77 =-0.29, p = 1; 0.3 lux: t 77 =-2.05, p = 0.46, Fig. 3 ). Duration of Cage Occupancy During the nocturnal active phase, male mouse lemurs spent most of their time in cage 1 near their next box and occasionally moved to cage 2 for feeding. Animals exposed to the CTL treatment, spent on average 25% of their time in cage 2 (Fig. 4 ). We observed a significant effect of the light treatment on the proportion of time spent in cage 2 (LMM: χ²=39.64, df = 3, p < 0.001). There was no significant difference in time spent in cage 2 between the CTL and 0.3 lux treatments (post-hoc test: t 33 = 0.166, P = 0.99). However, animals spent significantly less time in cage 2 during the 20 lux and 51.5 lux treatments compared to the CTL and 0.3 lux treatments (respectively post-hoc test: CTL-20 lux: t 33 =-2.91, p = 0.03; and CTL-51.5 lux: t 33 = -5.21, p < 0.001; 0.3 lux-20 lux: t 33 = 3.07, p = 0.02; 0.3 lux-51.5 lux: t 33 = 5.38, p < 0.001, Fig. 4 ), but we observed no significant difference between 20 lux and 51.5 lux treatments (t 33 = 2.30, p = 0.12, Fig. 4 ). Daily Caloric Food Intake There was no significant difference of daily caloric food intake between the CTL, 0.3 lux, 20 lux and 51.5 lux treatments (GLMM: χ²=0.32, df = 3, p = 0.95). DISCUSSION In this study, we demonstrate for the first time in a nocturnal primate that light pollution changes the preference of use of corridors, modifies the locomotor pattern, limits the ability of animals to move from one area to another and to efficiently exploit their environment according to light intensity, and thus fragments the habitat. Indeed, during the experiment, the total number of crossings through both corridors, illuminated or not, decreased according a light intensity-dependent relationship. Especially, the number of crossings decreased and the speed of crossing significantly increased when using the illuminated corridor. Consequently, light pollution limited the ability to move and changed the locomotor pattern with animals avoiding illumination. In addition, according to light intensity, mouse lemurs reduced the time spent in cage 2, i.e. the time allocated to foraging. Similar results have been previously reported in male mouse lemurs exposed to light pollution. Indeed, animals under illumination reduced their locomotor activity, spent less time outside their nest box, tended to spend less time feeding outside and brought more fruits into the nest box 35 . However, in both the previous and present study, there was no effect neither on the daily caloric food intake nor on body mass, most likely because food was provided ad libitum . Nevertheless, in another study, under constant illumination (free-running conditions), animals did not feed at all because of the strong inhibitory effect of light on general activity 27 . Similarly, in the Darwin’s leaf-eared mouse ( Phyllotis darwini ), animals exposed to simulated moonlight carried 40% of their food to the refuge site, consumed 15% less food during the experiment and lost 4.4 g in body mass (around 10% of the mean body weight in this species) in only one trial night 36 . This response probably reflected an anti-predator behaviour because light affects visual abilities in both nocturnal predators and preys and the perceived risk of predation increases with illumination of the environment 37,38 . Consequently, to minimize predation risk, preys limit their general activity even at the cost of loss of body mass. In the wild, including Madagascar, where food availability is highly unpredictable 39 , the impact on body mass could be increased. All these results confirm that light pollution fragments the habitat and limits the ability of animals to move and to effectively exploit their environment and its resources and could, therefore, threaten survival. In Madagascar, light pollution could exacerbate the detrimental effects of habitat loss and fragmentation observed in the past century on all lemur species. As they become increasingly confined to smaller and isolated forest patches, their population numbers, genetic diversity, and distribution have been altered, sometimes leading to local extinctions 40–42 . Given that light pollution in Malagasy protected areas has been relatively low but gradually increasing in the past decades 43 , it is crucial to promptly address and mitigate its potential future effects on habitat fragmentation. In our experiment, the apparatus provided two corridors. Interestingly, while the number of crossings through the illuminated corridor decreased according to light intensity, it increased proportionally through the black corridor. In addition, the speed of crossing through the black corridor did not change throughout the study. Concretely, when conditions of locomotion through one corridor were not optimal ( i.e. illumination), mouse lemurs reversed their preference on the other ( i.e. without illumination). However, this compensation was only partial because despite the presence of an optimal corridor, the total number of crossings through both corridors decreased according to light intensity. This point is crucial for the implementation of conservation plans. For example, in France, following the multiparty debate on the environment that took place in 2007, the conservation plan ‘green and blue Frame’ was initiated. This plan has for objective to reconstitute a network (reserves and corridors) on the national territory allowing animal species to communicate, to circulate, to feed and to reproduce within protected natural areas 44 . However, this plan has been initiated without recommendations relative to light pollution. Today, several associations for environmental protection ask for the implementation of a complementary ‘nocturnal frame’ to protect living organisms from the impacts of light pollution (ANPCEN, 2013), which has been included in the french Biodiversity Act since 2016 (Assemblée nationale, 2016). Considering that 28% of vertebrates and 64.4% of invertebrates live exclusively or partially at night, i.e. many species susceptible to be disturbed by light pollution 47 and considering the extent of light pollution, this inclusion is relevant. Indeed, in our study light pollution extended on 50 cm only and habitat fragmentation occurred on a fine scale. However, for a city of 10,000 inhabitants, the sky glow extends up to 20 km and can extend up to 120 km for a city of 1 million inhabitants 48 . Consequently, urban light pollution could fragment the habitat on a broad scale. Recently, Mu et al published an evaluation of light pollution in global protected areas from 1992 to 2018 and reported that there was a significant or a trend of increase in nighttime light in 53% of polluted protected areas in Europe, 78% in South America, and 81% in Africa 49 . In these impacted areas, light pollution, homogenizing the physical environment and being detrimental to photosensitive species, could reinforce biotic homogenization, threaten biodiversity and defeat conservation plans 50 . On the other hand, Japan and the United States of America (USA) exhibit opposite trends (In Japan, 85% of polluted protected areas demonstrated a significant or trend of decrease in nighttime light, while in the USA, the figure stood at 65%), highlighting the significant and positive impact that well-planned ecological conservation policies can have on mitigating light pollution 49 . Finally, our study shows that light intensities commonly found in urban area or recommended by the European standard EN-13201 on public lighting are sufficient to fragment the habitat. This point demonstrates the necessity to find a trade-off between human needs and environmental protection, by implementing public lighting policies, urbanization plans and conservation plans that take the light pollution factor into account. Declarations ACKNOWLEDGEMENTS We acknowledge Lauriane Dezaire and Eric Gueton for their assistance in animal care. Thomas Le Tallec was funded by a PhD grant [DRH/DS/n°1/2011] from the Ministère de l’Enseignement Supérieur et de la Recherche. AUTHORS CONTRIBUTION T.L., M.P. and M.T. designed the experimental protocol. T.L. made the experiments. C.H. made the data analysis. T.L. wrote the first draft of the manuscript. C.H. wrote parts of the manuscript. T.L., C.H., M.P. and M.T. reviewed the manuscript. DATA AVAILABILITY STATEMENT The data generated and analysed during the current study are available in the Figshare repository [https://doi.org/10.6084/m9.figshare.24047475]. 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Precision of the celestial compass in moonlight and sunlight. Philos. Trans. R. Soc. Lond. B. Biol. Sci. 366, 697–702 (2011). AFNOR. (Association Française de Normalisation). Norme française - Norme Européenne: NF EN 13201-2, éclairage public (2016). Le Tallec, T., Perret, M. & Théry, M. Light pollution modifies the expression of daily rhythms and behavior patterns in a nocturnal primate. PLoS One 8, (2013). Vasquez, R. A. Assessment of predation risk via illumination level: facultative central place foraging in the cricetif rodent Phyllotis darwini. Behav. Ecol. Sociobiol. 34, 375–381 (1994). Lima, S. & Dill, L. Behavorial decisions made under the risk predation: a review and prospectus. Can. J. Zool. 68, 619–640 (1990). Lima, S. L. Nonlethal Effects in the Ecology of Predator-Prey Interactions. Bioscience 48, 25–34 (1998). Dewar, R. E. & Richard, A. F. Evolution in the hypervariable environment of Madagascar. Proceedings of the National Academy of Sciences of the United States of America 104, 13723–13727 (2007). Aleixo-Pais, I. et al. The genetic structure of a mouse lemur living in a fragmented habitat in Northern Madagascar. Conserv. Genet. 20, 229–243 (2019). Andriatsitohaina, B. et al. Ecological fragmentation effects in mouse lemurs and small mammals in northwestern Madagascar. Am. J. Primatol. 82, 1–11 (2020). Schneider, N., Chikhi, L., Currat, M. & Radespiel, U. Signals of recent spatial expansions in the grey mouse lemur (Microcebus murinus). BMC Evol. Biol. 10, (2010). Zheng, Z. et al. Africa’s protected areas are brightening at night: A long-term light pollution monitor based on nighttime light imagery. Glob. Environ. Chang. 69, 102318 (2021). Centre de ressources Trame verte et bleue. Trame verte et bleue. (2007). ANPCEN - Association nationale pour la protection du ciel et de l’environnement Nocturnes. Les plaidoyers nationaux de l’ANPCEN. (2013). Assemblée nationale. Loi n° 2016–1087 du 8 août 2016 pour la reconquête de la biodiversité, de la nature et des paysages. J. Off. la République française 2016 (2016). Hölker, F., Wolter, C., Perkin, E. K. & Tockner, K. Light pollution as a biodiversity threat. Trends Ecol. Evol. 25, 681–2 (2010). Berry, R. The Darkness of the Night Sky. Int. Amat. Photoelectr. Photom. Commun. 9, 10–15 (1983). Mu, H. et al. Evaluation of light pollution in global protected areas from 1992 to 2018. Remote Sens. 13, 1–16 (2021). McKinney, M. L. Urbanization as a major cause of biotic homogenization. Biol. Conserv. 127, 247–260 (2006). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 18 Jan, 2024 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Major revision 10 Oct, 2023 Reviews received at journal 14 Sep, 2023 Reviewers agreed at journal 07 Sep, 2023 Reviewers invited by journal 04 Sep, 2023 Editor assigned by journal 30 Aug, 2023 Editor invited by journal 30 Aug, 2023 Submission checks completed at journal 30 Aug, 2023 First submitted to journal 31 Jul, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3220013","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":229841836,"identity":"db39cc86-0d5e-4336-8cac-3091794ef8af","order_by":0,"name":"Thomas Le Tallec","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA20lEQVRIie2PMQuCQBSAnwi6vHB9QfQbhECEgv5Kk5PuDRKGcC7Rb2lyvjhyst1daGgSAmmKrhqCBi+3oPuGx8fxPu4OQKP5ScxEDn8khUuhkTJAMBLgQAhgLR4J9knQfR2omIOxrpuY0LHLy7mKfQRbHHaKW1KXF4TDTZRPQymAQVApEkbcInSrQT4JpchHeqoku/Ib4bzC0yS8fZcw2DN5C6FZR+ybRBgpHbeEVAaeGUmxVH+xs3TfLNvZ2MlEfQnb1dixRdGZgPlWi56zc/2zbvpsazQazf9wB1IYPpCJOnjpAAAAAElFTkSuQmCC","orcid":"","institution":"UMR 7179 MECADEV, Centre National de la Recherche Scientifique, Muséum National d’Histoire Naturelle","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Thomas","middleName":"Le","lastName":"Tallec","suffix":""},{"id":229841837,"identity":"8b94c57e-8270-4258-be96-fa2e128904ad","order_by":1,"name":"Clara Hozer","email":"","orcid":"","institution":"UMR 7179 MECADEV, Centre National de la Recherche Scientifique, Muséum National d’Histoire Naturelle","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Clara","middleName":"","lastName":"Hozer","suffix":""},{"id":229841838,"identity":"b05ce73a-bd4d-4620-a2fc-3d8189110a9a","order_by":2,"name":"Martine Perret","email":"","orcid":"","institution":"UMR 7179 MECADEV, Centre National de la Recherche Scientifique, Muséum National d’Histoire Naturelle","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Martine","middleName":"","lastName":"Perret","suffix":""},{"id":229841839,"identity":"f14231d1-98be-4b8f-83aa-3835c3ce2f08","order_by":3,"name":"Marc Théry","email":"","orcid":"","institution":"UMR 7179 MECADEV, Centre National de la Recherche Scientifique, Muséum National d’Histoire Naturelle","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Marc","middleName":"","lastName":"Théry","suffix":""}],"badges":[],"createdAt":"2023-07-31 09:29:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3220013/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3220013/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-024-51853-7","type":"published","date":"2024-01-18T15:00:50+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":42647464,"identity":"fb46b704-478e-4122-9fcf-a79ebf734848","added_by":"auto","created_at":"2023-09-05 14:45:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":615313,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExperimental apparatus\u003c/strong\u003e. Mouse lemurs were housed individually in an apparatus consisting of two cages (1 and 2) connected by two tubes (black and transparent). The sleeping box was placed in cage 1, whereas food was provided in cage 2. Four yellow LEDs were regularly placed under the transparent tube to illuminate it with different light intensities from 0 to 51.5 lux.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3220013/v1/99fa41b6d48f3217e5804ea8.png"},{"id":42647465,"identity":"16d04e56-4359-41a5-ba49-c685e447b51f","added_by":"auto","created_at":"2023-09-05 14:45:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1419732,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTotal number of crossings (A) and number of crossings for black and transparent tubes (B)\u003c/strong\u003e. The total number of crossings decreased in the 20 lux and 51.5 lux treatments compared to the CTL treatment. Additionally, the number of crossings increased significantly for the black tube and decreased significantly for the transparent tube according to a light intensity-dependent relationship. a-b-c - differences for the total number of crossings between light treatments (CTL, 0.3 lux, 20 lux or 51.5 lux); a\u003csub\u003e1\u003c/sub\u003e,b\u003csub\u003e1\u003c/sub\u003e – significant differences for the number of crossings of the black tube between light treatments; a\u003csub\u003e2\u003c/sub\u003e-b\u003csub\u003e2\u003c/sub\u003e – significant differences for the number of crossings of the transparent tube between light treatments. *** - significant differences (p\u0026lt;0.001) for the number of crossings between the black tube and the transparent tube. N\u003csub\u003eb\u003c/sub\u003e = number of crossings the black tube; N\u003csub\u003et \u003c/sub\u003e= number of crossings the transparent tube.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3220013/v1/c6ca7b4e67ebd17922da42b0.png"},{"id":42647467,"identity":"b6196ab3-1214-4c53-9363-ecbc444b7b7e","added_by":"auto","created_at":"2023-09-05 14:45:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1426160,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSpeed of crossing black and transparent tubes.\u003c/strong\u003e The mean speed increased significantly for the transparent tube according to a light intensity-dependent relationship but remained constant in the black tube. a\u003csub\u003e1\u003c/sub\u003e,b\u003csub\u003e1\u003c/sub\u003e– significant differences for the mean speed of the transparent tube between light treatments; *** - significant differences (p\u0026lt;0.001) for the number of crossings between the black tube and the transparent tube. The speed of crossing was significantly higher through the transparent tube compared to the black tube in the 20 lux and the 51.5 lux treatments. S\u003csub\u003eb\u003c/sub\u003e = mean speed in the black tube; S\u003csub\u003et \u003c/sub\u003e= mean speed in the transparent tube.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3220013/v1/2e6adffdac5353281dafd6b0.png"},{"id":42648755,"identity":"0c95ef15-87c2-4f15-8d4c-15291171c83e","added_by":"auto","created_at":"2023-09-05 14:53:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1060428,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProportion of time spent in cage 2\u003c/strong\u003e. Male mouse lemurs spent significantly less time in cage 2 during the 20 lux and the 51.5 lux treatments compared to the control (CTL) and the 0.3 lux treatments. a - significant differences for the proportion of occupancy of cage 2 between light treatments.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3220013/v1/1ff72344e9be438b64ccd3f2.png"},{"id":49978588,"identity":"c358641a-2d72-48b6-91d0-a7b247d3b935","added_by":"auto","created_at":"2024-01-22 15:07:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":893666,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3220013/v1/667ab120-3a1e-4283-ba62-e5b54f439112.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Light pollution and habitat fragmentation in the grey mouse lemur","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHabitat fragmentation, which is one major factor implicated in the global decline of populations and species \u003csup\u003e1\u0026ndash;3\u003c/sup\u003e, refers to the process of subdividing a continuous habitat into smaller discontinuous patches \u003csup\u003e4\u003c/sup\u003e. Specifically, habitat fragmentation simultaneously involves four processes: 1) reduction in habitat amount; 2) increase in number of habitat patches; 3) decrease in size of patches; 4) increase in isolation of patches \u003csup\u003e5\u003c/sup\u003e. In turn, these processes affect abiotic and biotic habitat conditions and, consequently, modify ecosystem equilibrium. Depending on species, these changes can have either positive or negative consequences on survival and fitness \u003csup\u003e6\u0026ndash;8\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOver the past decades, extensive research has investigated habitat fragmentation related mechanisms \u003csup\u003e9\u0026ndash;14\u003c/sup\u003e but only few studies have taken into account the introduction of artificial light in the nocturnal environment and its potential consequences on habitat fragmentation (Chall\u0026eacute;at et al., 2021; Laforge et al., 2019; Schirmer et al., 2019; Eisenbeis, 2006). However, light pollution has demonstrable effects on organisms\u0026rsquo; behaviour, such as changes in orientation or attraction exerted by the illuminated environment, the \u0026lsquo;flight-to-light\u0026rsquo; behaviour of nocturnal insects and migratory birds around artificial light being the best documented effect \u003csup\u003e18,19\u003c/sup\u003e. As a result, these behavioral disturbances can affect locomotion and migration patterns \u003csup\u003e20\u003c/sup\u003e and contribute to habitat fragmentation. There are two scenarios identified in which light pollution limits locomotion and migration: 1) the \u0026lsquo;captivity\u0026rsquo; effect when organisms are disturbed from their normal activity by contact with artificial light and are unable to escape from the proximity of lighting, and 2) the \u0026lsquo;crash barrier\u0026rsquo; effect when organisms are disturbed during long-distance movement by artificial light encountered in their travel path. Artificial light prevents organisms from following their original flyway and makes them unable to leave the illuminated environment.\u003c/p\u003e \u003cp\u003eIn mammals, few studies have documented habitat fragmentation through the effects of light pollution, whereas it is thought that mammals could be, along with birds, more behaviourally affected by artificial light because of the physical structure of their eye \u003csup\u003e21\u003c/sup\u003e. In a study of dispersing puma (\u003cem\u003ePuma concolor\u003c/em\u003e), artificial light was detrimental for juveniles exploring new habitat, as they moved away from the urban artificial lights and navigated toward the darkest horizon, especially in a road undercrossing or in open habitats \u003csup\u003e22\u003c/sup\u003e. In bats, light pollution fragmented commuting routes with associated negative conservation consequences \u003csup\u003e23,24\u003c/sup\u003e. Specifically, slower-flying bats (\u003cem\u003eRhinolophus hipposideros\u003c/em\u003e and \u003cem\u003eMyotis\u003c/em\u003e spp.) avoided artificial light due to light-dependent predation risk. Similarly, another study highlighted that nighttime artificial illumination reduced total home size and home range overlap between conspecifics of two mammal species, the bank vole (\u003cem\u003eMyodes glareolus\u003c/em\u003e) and the striped field mouse (\u003cem\u003eApodemus agrarius\u003c/em\u003e) \u003csup\u003e25\u003c/sup\u003e. In a study assessing the effect of artificial light on wildlife use of a passage structure submitted to different light treatments, the authors demonstrated that several mammal species, such as the columbia black-tailed deer (\u003cem\u003eOdocoileus hemionus columbianus\u003c/em\u003e), the deer mouse (\u003cem\u003ePeromyscus maniculatus\u003c/em\u003e) or the opossum (\u003cem\u003eDidelphis virginiana\u003c/em\u003e) traversed a bridge under-road passage much less when sections or neighboring sections were lit compared to when none were, suggesting avoidance due to direct or nearby presence of artificial light \u003csup\u003e26\u003c/sup\u003e. These studies point out that light pollution, by changing movement patterns and interindividual interactions, establishes barriers to connectivity on the landscape and can isolate populations. This can result in reducing mammals\u0026rsquo; ability to maintain genetic diversity, increasing their susceptibility to disturbance and disease, and limiting their access to resources, potentially leading to fitness consequences on the population level. These studies also highlight the need of finding mitigation solution of artificial light at night, such as under-road unlit corridors, and to examine their efficiency.\u003c/p\u003e \u003cp\u003eTo explore the effects of light pollution on locomotion in mammals and to extend the knowledge on habitat fragmentation, we conducted an experimental study on male grey mouse lemurs (\u003cem\u003eMicrocebus murinus\u003c/em\u003e). The grey mouse lemur, a Malagasy primate, is a convenient model to study the impact of light pollution because of the strong dependence of its behaviours, biological rhythms and physiological functions on photoperiod in the wild and in captivity and of the strong inhibitory effect of light on its general activity \u003csup\u003e27\u0026ndash;29\u003c/sup\u003e. In this study, we investigated the effect of light pollution on behavioural activities of male mouse lemurs by testing the choice for travelling between a non-illuminated corridor and a corridor illuminated by different light intensities, increasing from full moon to streetlight (from 0.3 lux to 51.5 lux). In this photophobic and nocturnal mammal, we predict that male mouse lemurs will prefer the use of the non-illuminated corridor and this preference will increase according to a light intensity-dependent relationship.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eAnimals\u003c/h2\u003e \u003cp\u003eWe included 12 adult male grey mouse lemurs (35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0 months) in this study, all in active sexual state. In captivity, seasonal variations of behaviours, daily rhythms and physiological functions are entrained by alternating 6-months periods of winter-like short-days photoperiod (SD; light/dark 10:14) and summer-like long-days photoperiod (LD; light/dark 14:10) under artificial light. Mouse lemurs were studied during 4 consecutive nights in mid-summer. They were housed individually at constant ambient temperature (24\u0026ndash;26\u0026deg;C) and relative humidity (55%) with food in excess including a homemade milky mixture (46 kJ/day) and fresh fruits (18.5 kJ/day) delivered every day during the diurnal resting phase and water available \u003cem\u003ead libitum\u003c/em\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEthical Note\u003c/h2\u003e \u003cp\u003e All experiments were performed in the laboratory breeding-colony of Brunoy (UMR 7179 CNRS/MNHN, France; agreement n\u0026deg; E91-114-1 from the Direction D\u0026eacute;partementale de la Protection des Populations de l\u0026rsquo;Essonne) under the authorization n\u0026deg; Ce5/2011/067 from the Charles Darwin Ethics Committee in Animal Experiment and the Internal Review Board of the UMR 7179. All experiments were conducted under personal license to T. Le Tallec (authorization n\u0026deg; A91-621 from the Direction D\u0026eacute;partementale de la Protection des Populations de l\u0026rsquo;Essonne) and followed guidelines approved by the Association for the Study of Animal Behaviour and by the Animal Behavior Society\u003csup\u003e30\u003c/sup\u003e. The study is reported in accordance with ARRIVE guidelines (to reduce the number of animals involved in the experiment, animals were used as their own control, outcome measures are clearly defined, statistical analysis is fully detailed and the code is available on the following Figshare repository: [\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.6084/m9.figshare.24047478\u003c/span\u003e\u003cspan address=\"10.6084/m9.figshare.24047478\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e], the species, sex and age of animals are reported, the experimental procedures are described in detail).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eApparatus\u003c/h2\u003e \u003cp\u003eAnimals were housed individually in an apparatus consisting of two cages (50\u0026times;50\u0026times;50 cm) connected by two Plexiglas\u0026reg; tubes (respectively opaque and transparent; length: 50 cm; diameter: 8 cm). Cage 1 was enriched with two tree branches and a nest box. Cage 2 was enriched with two tree branches and a feeder. The black opaque tube did not allow the transmission of any light. The transparent tube allowed the transmission of 92% of external light. Consequently, to feed after leaving the nesting box in cage 1, animals needed to cross one of the two tubes to reach cage 2. To rest and leave from cage 2, animals needed to cross again one of the two tubes to return to cage 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eExperimental protocol\u003c/h2\u003e \u003cp\u003eDuring 4 nights, the transparent tube was illuminated by four yellow LEDs (model L-1503YD, Kingbright, Taipei, Taiwan) regularly distributed every 12.5 cm (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). LEDs simulated the irradiance spectra of streetlights with high pressure sodium lamps, the most common artificial light used for outdoor lighting characterized by emission lines from 569 to 616 nm \u003csup\u003e31\u003c/sup\u003e. Night 0 was a habituation period without any light treatment. Each following night, the transparent tube received a different illumination treatment with a specific light intensity: 1) 0 nmol photons.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in night 1 (control treatment, CTL); 2) 3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 nmol photons.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in night 2 (0.3 lux treatment), corresponding to the intensity of full moon \u003csup\u003e32\u003c/sup\u003e, the most important source of natural light at night \u003csup\u003e33\u003c/sup\u003e; 3) 246.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9 nmol photons.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in night 3 (20 lux treatment), corresponding to the minimal light intensity to maintain in urban areas as recommended by the European standard EN-13201-02 on public lighting \u003csup\u003e34\u003c/sup\u003e; 4) 628.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1 nmol photons.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in night 4 (51.5 lux treatment), corresponding to the average light intensity of streetlights with high pressure sodium lamps sampled in the city (77 lamps). For each LED, the average light intensity was calibrated before the experiment using a JAZ spectrometer (Ocean Optics, Dunedin, Florida, USA) between 300\u0026ndash;700 nm. Before the experiment, we randomly determined the initial position of each tube (black or transparent) that was reversed between each light treatment, to prevent any laterality effect. In addition, before the experiment and between each light treatment, both tubes were cleaned to remove any olfactory cues. Daytime light was provided by fluorescent lamps (1 000 lux), placed in the ceiling of the experimental room.\u003c/p\u003e \u003cp\u003eThroughout the experiment, the activity of each animal was filmed all night (10 hours) using an infrared camera (Handycam HDR-SR7, Sony, Tokyo, Japan) placed above the apparatus. We then determined for each light treatment the total number of crossings of both tubes. In addition, we determined for the black tube and the transparent tube separately the respective number of crossings (Nb and Nt) and the speed of crossing (Sb and St in cm.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The animal was considered to be in a tube when its four paws were seen in it. We also determined for each light treatment the proportion of time spent in each cage. The animal was considered to be in a cage when its four paws were seen in it. Before the experiment, values of body mass were controlled to ensure of their homogeneity (76.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9 g). Daily caloric food intake (CI in kJ) was calculated each day for each animal from the difference between provided and remaining food mass corrected for dehydration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eAll analyses were performed with R version 2.14.2 (R Development Core Team, 2001). We performed two mixed linear models (LMMs) using the \u0026lsquo;lmer\u0026rsquo; function of the \u0026lsquo;lme4\u0026rsquo; package with individuals\u0026rsquo; identity as random variable to assess the effects of light treatment (CTL, 0.3 lux, 20 lux or 51.5 lux), tube (transparent or black) and the interaction between light treatment and tube on the number of crossings and on the mean speed of crossing. We further checked the distribution of residuals with \u0026lsquo;qqPlot\u0026rsquo; function of the \u0026lsquo;car\u0026rsquo; package for LMMs, and with Shapiro tests. The residuals did not comply with normality in the mean speed model, so we used the \u0026lsquo;boxcox\u0026rsquo; function of the \u0026lsquo;MASS\u0026rsquo; package to estimate an optimal power transformation that maximizes the normality of the transformed variable. Subsequently, we reran the model by applying the power transformation of -1.5 to the mean speed variable. We then ran post-hoc tests using the function \u0026lsquo;emmeans\u0026rsquo; of the \u0026lsquo;emmeans\u0026rsquo; package with the Tukey correction, in order to determine which specific groups differed from each other. We ran another LMM with individuals\u0026rsquo; identity as random variable to assess the effect of light treatment on the proportion of occupancy of cage 2. Finally, we ran a generalized LMM with individuals\u0026rsquo; identity as random variable and a poisson error structure to assess the effect of light treatment on the caloric intake. The probability level for statistical significance was \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05. All values are presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of the means.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eNumber of crossings and speed of crossing\u003c/h2\u003e \u003cp\u003eWe observed a significant effect of the light treatment on the total number of tubes crossings (LMM: χ\u0026sup2;=40.94, df\u0026thinsp;=\u0026thinsp;3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The total number of tubes crossings was not significantly different between the CTL and the 0.3 lux treatment (post-hoc test: t\u003csub\u003e77\u003c/sub\u003e = -0.39, p\u0026thinsp;=\u0026thinsp;0.98, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), nor between the 0.3 lux and the 20 lux treatments (post-hoc test: \u003cem\u003et\u003c/em\u003e\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.40, p\u0026thinsp;=\u0026thinsp;0.09, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), but was significantly reduced during the 20 lux and 51.5 lux treatments compared to the CTL treatment (respectively post-hoc tests: CTL-20 lux: \u003cem\u003et\u003c/em\u003e\u003csub\u003e77\u003c/sub\u003e = -2.79, p\u0026thinsp;=\u0026thinsp;0.03 and CTL-51.5 lux: \u003cem\u003et\u003c/em\u003e\u003csub\u003e77\u003c/sub\u003e = -5.67, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), and was significantly reduced during the 51.5 lux treatment compared to the 0.3 and 20 lux treatments (respective post-hoc tests: 0.3lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;5.27, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 and 20 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.88, p\u0026thinsp;=\u0026thinsp;0.03, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). We also observed a significantly higher total number of crossings in the black tube than in the transparent tube (LMM: χ\u0026sup2;=207.06, df\u0026thinsp;=\u0026thinsp;1, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), as well as a significant interaction between the tube and the light treatment on the number of crossings (LMM: χ\u0026sup2;=209.53, df\u0026thinsp;=\u0026thinsp;3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). While the number of crossings in the black tube was not different between the CTL, 0.3 lux and 20 lux treatments but significantly higher in the 51.5 lux treatment compared to the CTL and 0.3 lux treatments (respective post-hoc tests: CTL-0.3 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.26, p\u0026thinsp;=\u0026thinsp;1.00; CTL-20 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.16, p\u0026thinsp;=\u0026thinsp;0.38; CTL-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;5.06, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-20 lux: t\u003csub\u003e77\u003c/sub\u003e=-1.90, p\u0026thinsp;=\u0026thinsp;0.55; 0.3 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-4.80, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 20 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-2.90, p\u0026thinsp;=\u0026thinsp;0.09, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), the number of crossings the transparent tube significantly decreased in the 20 lux and 51.5 lux treatments compared to the CTL and the 0.3 lux treatments (respective post-hoc tests: CTL-0.3 lux: t\u003csub\u003e77\u003c/sub\u003e=-0.82, p\u0026thinsp;=\u0026thinsp;0.99; CTL-20 lux: t\u003csub\u003e77\u003c/sub\u003e=-6.11, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; CTL-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-13.07, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-20 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;5.29, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;12.25, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 20 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;6.96, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), but not between the CTL and the 0.3 lux treatments (t\u003csub\u003e77\u003c/sub\u003e=-0.82, p\u0026thinsp;=\u0026thinsp;0.99, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Finally, the number of crossings the black tube was significantly higher than the transparent tube in the 20 lux and 51.5 lux treatment (respective post-hoc tests: 20 lux: t77\u0026thinsp;=\u0026thinsp;8.60, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 and 51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;18.46, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) but not in the CTL and 0.3 lux treatments (respective post-hoc tests: CTL: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.32, p\u0026thinsp;=\u0026thinsp;1; 0.3 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1.40, p\u0026thinsp;=\u0026thinsp;0.85, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe observed a significant higher mean speed in the transparent tube than in the black tube (LMM: χ\u0026sup2;=154.12, df\u0026thinsp;=\u0026thinsp;1, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), as well as a significant interaction between the tube and the light treatment on the mean speed (LMM: χ\u0026sup2;=99.50, df\u0026thinsp;=\u0026thinsp;3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). While the mean speed in the black tube was not different between the different treatments (respective post-hoc tests: CTL-0.3 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.31, p\u0026thinsp;=\u0026thinsp;1; CTL-20 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.95, p\u0026thinsp;=\u0026thinsp;0.98; CTL-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.85, p\u0026thinsp;=\u0026thinsp;0.99; 0.3 lux-20 lux: t\u003csub\u003e77\u003c/sub\u003e=-0.64, p\u0026thinsp;=\u0026thinsp;1; 0.3 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-0.54, p\u0026thinsp;=\u0026thinsp;1; 20 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.10, p\u0026thinsp;=\u0026thinsp;1, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), the mean speed in the transparent tube was significantly higher in the 20 lux and 51.5 lux treatments compared to the CTL and the 0.3 lux treatments (respective post-hoc tests: CTL-20 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;12.38, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; CTL-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;25.22 p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-20 lux: t\u003csub\u003e77\u003c/sub\u003e=-10.31, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-23.15, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), as well as in the 51.5 lux treatment compared to the 20 lux treatment (20 lux-51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-12.84, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), but not between the CTL and the 0.3 lux treatments (t\u003csub\u003e77\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.07, p\u0026thinsp;=\u0026thinsp;0.44, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Finally, the mean speed in the transparent tube was significantly higher than in the black tube in the 20 lux and 51.5 lux treatment (respective post-hoc tests: 20 lux: t\u003csub\u003e77\u003c/sub\u003e=-11.72, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 and 51.5 lux: t\u003csub\u003e77\u003c/sub\u003e=-24.66, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) but not in the CTL and 0.3 lux treatments (respective post-hoc tests: CTL: t\u003csub\u003e77\u003c/sub\u003e=-0.29, p\u0026thinsp;=\u0026thinsp;1; 0.3 lux: t\u003csub\u003e77\u003c/sub\u003e=-2.05, p\u0026thinsp;=\u0026thinsp;0.46, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eDuration of Cage Occupancy\u003c/h2\u003e \u003cp\u003eDuring the nocturnal active phase, male mouse lemurs spent most of their time in cage 1 near their next box and occasionally moved to cage 2 for feeding. Animals exposed to the CTL treatment, spent on average 25% of their time in cage 2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). We observed a significant effect of the light treatment on the proportion of time spent in cage 2 (LMM: χ\u0026sup2;=39.64, df\u0026thinsp;=\u0026thinsp;3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). There was no significant difference in time spent in cage 2 between the CTL and 0.3 lux treatments (post-hoc test: t\u003csub\u003e33\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.166, P\u0026thinsp;=\u0026thinsp;0.99). However, animals spent significantly less time in cage 2 during the 20 lux and 51.5 lux treatments compared to the CTL and 0.3 lux treatments (respectively post-hoc test: CTL-20 lux: t\u003csub\u003e33\u003c/sub\u003e =-2.91, p\u0026thinsp;=\u0026thinsp;0.03; and CTL-51.5 lux: t\u003csub\u003e33\u003c/sub\u003e = -5.21, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; 0.3 lux-20 lux: t\u003csub\u003e33\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;3.07, p\u0026thinsp;=\u0026thinsp;0.02; 0.3 lux-51.5 lux: t\u003csub\u003e33\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;5.38, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), but we observed no significant difference between 20 lux and 51.5 lux treatments (t\u003csub\u003e33\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.30, p\u0026thinsp;=\u0026thinsp;0.12, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eDaily Caloric Food Intake\u003c/h2\u003e \u003cp\u003eThere was no significant difference of daily caloric food intake between the CTL, 0.3 lux, 20 lux and 51.5 lux treatments (GLMM: χ\u0026sup2;=0.32, df\u0026thinsp;=\u0026thinsp;3, p\u0026thinsp;=\u0026thinsp;0.95).\u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn this study, we demonstrate for the first time in a nocturnal primate that light pollution changes the preference of use of corridors, modifies the locomotor pattern, limits the ability of animals to move from one area to another and to efficiently exploit their environment according to light intensity, and thus fragments the habitat.\u003c/p\u003e \u003cp\u003eIndeed, during the experiment, the total number of crossings through both corridors, illuminated or not, decreased according a light intensity-dependent relationship. Especially, the number of crossings decreased and the speed of crossing significantly increased when using the illuminated corridor. Consequently, light pollution limited the ability to move and changed the locomotor pattern with animals avoiding illumination. In addition, according to light intensity, mouse lemurs reduced the time spent in cage 2, \u003cem\u003ei.e.\u003c/em\u003e the time allocated to foraging. Similar results have been previously reported in male mouse lemurs exposed to light pollution. Indeed, animals under illumination reduced their locomotor activity, spent less time outside their nest box, tended to spend less time feeding outside and brought more fruits into the nest box \u003csup\u003e35\u003c/sup\u003e. However, in both the previous and present study, there was no effect neither on the daily caloric food intake nor on body mass, most likely because food was provided \u003cem\u003ead libitum\u003c/em\u003e. Nevertheless, in another study, under constant illumination (free-running conditions), animals did not feed at all because of the strong inhibitory effect of light on general activity \u003csup\u003e27\u003c/sup\u003e. Similarly, in the Darwin\u0026rsquo;s leaf-eared mouse (\u003cem\u003ePhyllotis darwini\u003c/em\u003e), animals exposed to simulated moonlight carried 40% of their food to the refuge site, consumed 15% less food during the experiment and lost 4.4 g in body mass (around 10% of the mean body weight in this species) in only one trial night \u003csup\u003e36\u003c/sup\u003e. This response probably reflected an anti-predator behaviour because light affects visual abilities in both nocturnal predators and preys and the perceived risk of predation increases with illumination of the environment \u003csup\u003e37,38\u003c/sup\u003e. Consequently, to minimize predation risk, preys limit their general activity even at the cost of loss of body mass. In the wild, including Madagascar, where food availability is highly unpredictable \u003csup\u003e39\u003c/sup\u003e, the impact on body mass could be increased. All these results confirm that light pollution fragments the habitat and limits the ability of animals to move and to effectively exploit their environment and its resources and could, therefore, threaten survival. In Madagascar, light pollution could exacerbate the detrimental effects of habitat loss and fragmentation observed in the past century on all lemur species. As they become increasingly confined to smaller and isolated forest patches, their population numbers, genetic diversity, and distribution have been altered, sometimes leading to local extinctions \u003csup\u003e40\u0026ndash;42\u003c/sup\u003e. Given that light pollution in Malagasy protected areas has been relatively low but gradually increasing in the past decades \u003csup\u003e43\u003c/sup\u003e, it is crucial to promptly address and mitigate its potential future effects on habitat fragmentation.\u003c/p\u003e \u003cp\u003eIn our experiment, the apparatus provided two corridors. Interestingly, while the number of crossings through the illuminated corridor decreased according to light intensity, it increased proportionally through the black corridor. In addition, the speed of crossing through the black corridor did not change throughout the study. Concretely, when conditions of locomotion through one corridor were not optimal (\u003cem\u003ei.e.\u003c/em\u003e illumination), mouse lemurs reversed their preference on the other (\u003cem\u003ei.e.\u003c/em\u003e without illumination). However, this compensation was only partial because despite the presence of an optimal corridor, the total number of crossings through both corridors decreased according to light intensity. This point is crucial for the implementation of conservation plans. For example, in France, following the multiparty debate on the environment that took place in 2007, the conservation plan \u0026lsquo;green and blue Frame\u0026rsquo; was initiated. This plan has for objective to reconstitute a network (reserves and corridors) on the national territory allowing animal species to communicate, to circulate, to feed and to reproduce within protected natural areas \u003csup\u003e44\u003c/sup\u003e. However, this plan has been initiated without recommendations relative to light pollution. Today, several associations for environmental protection ask for the implementation of a complementary \u0026lsquo;nocturnal frame\u0026rsquo; to protect living organisms from the impacts of light pollution (ANPCEN, 2013), which has been included in the french Biodiversity Act since 2016 (Assembl\u0026eacute;e nationale, 2016). Considering that 28% of vertebrates and 64.4% of invertebrates live exclusively or partially at night, \u003cem\u003ei.e.\u003c/em\u003e many species susceptible to be disturbed by light pollution \u003csup\u003e47\u003c/sup\u003e and considering the extent of light pollution, this inclusion is relevant. Indeed, in our study light pollution extended on 50 cm only and habitat fragmentation occurred on a fine scale. However, for a city of 10,000 inhabitants, the sky glow extends up to 20 km and can extend up to 120 km for a city of 1\u0026nbsp;million inhabitants \u003csup\u003e48\u003c/sup\u003e. Consequently, urban light pollution could fragment the habitat on a broad scale. Recently, Mu et al published an evaluation of light pollution in global protected areas from 1992 to 2018 and reported that there was a significant or a trend of increase in nighttime light in 53% of polluted protected areas in Europe, 78% in South America, and 81% in Africa \u003csup\u003e49\u003c/sup\u003e. In these impacted areas, light pollution, homogenizing the physical environment and being detrimental to photosensitive species, could reinforce biotic homogenization, threaten biodiversity and defeat conservation plans \u003csup\u003e50\u003c/sup\u003e. On the other hand, Japan and the United States of America (USA) exhibit opposite trends (In Japan, 85% of polluted protected areas demonstrated a significant or trend of decrease in nighttime light, while in the USA, the figure stood at 65%), highlighting the significant and positive impact that well-planned ecological conservation policies can have on mitigating light pollution \u003csup\u003e49\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFinally, our study shows that light intensities commonly found in urban area or recommended by the European standard EN-13201 on public lighting are sufficient to fragment the habitat. This point demonstrates the necessity to find a trade-off between human needs and environmental protection, by implementing public lighting policies, urbanization plans and conservation plans that take the light pollution factor into account.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eACKNOWLEDGEMENTS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge Lauriane Dezaire and Eric Gueton for their assistance in animal care.\u0026nbsp;Thomas Le Tallec was funded by a PhD grant [DRH/DS/n\u0026deg;1/2011] from the Minist\u0026egrave;re de l\u0026rsquo;Enseignement Sup\u0026eacute;rieur et de la Recherche.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAUTHORS CONTRIBUTION\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eT.L., M.P. and M.T. designed the experimental protocol. T.L. made the experiments. C.H. made the data analysis. T.L. wrote the first draft of the manuscript. C.H. wrote parts of the manuscript. T.L., C.H., M.P. and M.T. reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDATA AVAILABILITY STATEMENT\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data generated and analysed during the current study are available in the Figshare repository [https://doi.org/10.6084/m9.figshare.24047475].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCOMPETING INTERESTS STATEMENT\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRybicki, J. \u0026amp; Hanski, I. Species-area relationships and extinctions caused by habitat loss and fragmentation. Ecol. Lett. 16, 27\u0026ndash;38 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHanski, I. Habitat fragmentation and species richness. J. Biogeogr. 42, 989\u0026ndash;993 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKeinath, D. 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Conserv. 127, 247\u0026ndash;260 (2006).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"artificial light, corridor, habitat fragmentation, light pollution, mammal, Microcebus murinus, mouse lemur","lastPublishedDoi":"10.21203/rs.3.rs-3220013/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3220013/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLight pollution, by changing organisms\u0026rsquo; behavior, affects locomotion, migration and can ultimately fragment the habitat. To investigate the effects of light pollution on habitat fragmentation, we conducted an experimental study on a nocturnal and photosensitive primate, the grey mouse lemur (\u003cem\u003eMicrocebus murinus\u003c/em\u003e). Twelve males were housed individually in an apparatus with two cages connected by two corridors, opaque and transparent. During 4 nights, the transparent corridor was illuminated by specific light intensities: 0 lux, 0.3 lux, 20 lux and 51.5 lux corresponding respectively to total darkness, full moon, minimal intensity recommended by the European standard EN-13201 on public lighting, and to light pollution recorded in an urban area. Each night, general activity, use of corridors and cage occupancy were recorded using an infrared camera. For the first time in a nocturnal primate, results demonstrate that light pollution changes the preference of use of corridors, modifies the locomotor pattern and limits the ability of animals to efficiently exploit their environment according to a light intensity-dependent relationship. However, results indicate that a dark corridor allows partial compensation partly preserving general activities. This study highlights the necessity to consider light pollution during the implementation of conservation plans and the relevance of nocturnal frames.\u003c/p\u003e","manuscriptTitle":"Light pollution and habitat fragmentation in the grey mouse lemur","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-09-05 14:45:36","doi":"10.21203/rs.3.rs-3220013/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2023-10-10T13:25:33+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-09-14T06:31:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"de3f1593-e8e2-4a4f-b22c-b443b81dea67","date":"2023-09-07T09:54:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-09-04T07:44:37+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-08-30T14:29:34+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2023-08-30T09:58:11+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2023-08-30T09:51:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2023-07-31T09:27:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e51a257c-5329-4c86-a7a6-fc6e00d6aa71","owner":[],"postedDate":"September 5th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":24348335,"name":"Biological sciences/Ecology/Behavioural ecology"},{"id":24348336,"name":"Biological sciences/Ecology/Conservation"},{"id":24348337,"name":"Biological sciences/Ecology/Urban ecology"},{"id":24348338,"name":"Biological sciences/Zoology/Animal behaviour"}],"tags":[],"updatedAt":"2024-01-22T15:02:59+00:00","versionOfRecord":{"articleIdentity":"rs-3220013","link":"https://doi.org/10.1038/s41598-024-51853-7","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2024-01-18 15:00:50","publishedOnDateReadable":"January 18th, 2024"},"versionCreatedAt":"2023-09-05 14:45:36","video":"","vorDoi":"10.1038/s41598-024-51853-7","vorDoiUrl":"https://doi.org/10.1038/s41598-024-51853-7","workflowStages":[]},"version":"v1","identity":"rs-3220013","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3220013","identity":"rs-3220013","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}