1 Impact of weather conditions, seasonality and moonlight on the use of artificial canopy 1 bridges by nocturnal arboreal mammals 2 K.A.I. Nekaris 1 *, Victoria Handby 1 , Marco Campera 1 3 1 Nocturnal Primate Research Group, Department of Social Sciences, Oxford Brookes University, Oxford, UK 4 *corresponding author email address: anekaris@brookes.ac.uk 5 Other email addresses: mcampera@brookes.ac.uk; v.handby94@hotmail.co.uk 6 7 ORCID: K.A.I. Nekaris: 0000-0001-5523-7353 Marco Campera: 0000-0003-2643-8329 Victoria Handby: 0000- 8 0001-9273-6776 9 10 Abstract 11 Natural and artificial canopy bridges can be used to mitigate the effects of habitat fragmentation. Understanding 12 the ecological factors that influence bridge use is imperative to the effective design and placement of this 13 potential conservation intervention. Moonlight, seasonality and weather may influence the cost and risk of using 14 bridges, potentially reducing their effectiveness. We installed five artificial waterline bridges and, between 2017 15 and 2019, monitored via camera trapping their use by Javan palm civets Paradoxurus musanga javanicus and 16 Javan slow lorises Nycticebus javanicus. We used a weather station to record microclimate data (temperature 17 and relative humidity) and calculated the illumination percentage of the moon. We tested the influence of moon 18 luminosity, relative humidity, seasonality (Julian day) and temperature on the frequency of bridge use via 19 Generalised Additive Models. Camera traps captured 938 instances of bridge use by civets, which was 20 significantly lower than the reference value at moon luminosity >90%, temperatures >20°C, humidity >90%, and 21 during the drier period (May-July). Camera traps captured 1036 instances of bridge use by lorises, which was 22 significantly lower than the reference value during the drier period and higher than the reference value at 23 temperatures >20°C. Lorises showed peaks in bridge use close to sunset and sunrise whereas civets showed 24 peaks around 2 h after sunset and 2 h before sunrise. Our study illustrates the utility of simple-to-construct 25 bridges by two sympatric nocturnal mammals facing severe habitat loss, with bridge use differing between those 26 species according to abiotic factors. In particular, less use by both taxa during the drier season could suggest 27 modifying placement of bridges or providing another intervention during that time. Camera traps were an 28 excellent mechanism to record these differences and to validate the importance of the bridges, including during 29 inclement weather and dark nights, when observations would be more difficult for human observers. By 30 understanding the influence that abiotic factors have on the use of artificial bridges, we can improve bridge 31 placement and construction to encourage use by a variety of species, particularly those threatened by habitat 32 fragmentation. 33 34 Key words: Paradoxurinae, Lorisinae lunarphobic, lunarphilic, wildlife crossings, fragmentation 35 36