Adverse effects of artificial illumination on bat drinking activity

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Running title: Effects of artificial illumination on drinking bats AbstractArtificial illumination at night (ALAN) alters many aspects of animal behaviour. Commuting and foraging bats have been found to be affected by ALAN, but no study has yet addressed the impact of lighting on drinking activity, despite its critical importance for bats. We experimentally illuminated cattle troughs used by drinking bats at four forest sites in Italy, and compared drinking activity and foraging activity under lit and dark conditions. We predicted that 1) the number of bat 2 species and drinking events will be lower under illumination and 2) forest bat species will be more affected than edge specialists. We recorded 2549 drinking events from 12 species or species groups, most of which decreased drinking activity under illumination. The effects of ALAN on drinking were stronger than on foraging. Forest species never drank when the light was on. Edge-foraging species reduced drinking activity while also increasing foraging under lit conditions. We highlight a previously overlooked negative effect of ALAN on bats, whose implications may be locally catastrophic. Given the importance of water sites for both bat foraging and drinking, their illumination should be forbidden, appropriately mitigated or, if necessary, compensated for with the creation of alternative drinking sites.

Effects of artificial illumination on drinking bats: a field test in forest and desert habitats

“…Overall, apart from the above-mentioned rare exceptions, light repels bats, especially forest species whose broad, short wings are tailored to manoeuvre in clutter but not to escape predators (Mathews et al, 2015;Russo et al, 2017). The few studies that have tested the effects of ALAN in the surroundings of a roost show that bats may vacate it (Rydell, Ekl€ of & S anchez-Navarro, 2017a) with potentially negative effects on bat welfare, survival and conservation status (Zeale et al, 2016;Rydell et al, 2017a).…”

“…All bats drink in flight and do so through a complex drinking manoeuvre (Tuttle, Chambers & Theimer, 2006;Russo, Cistrone & Jones, 2012;Russo et al, 2017). Drinking activity responds more strongly than foraging, and the effect concerns not only slowly flying forest species but also species that exploit illuminated sites for hunting, i.e.…”

“…Such areas comprise temperate forests or deserts, recently also exposed to ALAN because in many cases they are facing significant urban expansion (Al-Soliman, 1993;Richer, 2009;Polak et al, 2011). Russo et al (2017) tested the effect of ALAN at forest drinking sites by comparing drinking between paired short (10-min) time intervals during which light was switched on and off, respectively. Russo et al (2017) tested the effect of ALAN at forest drinking sites by comparing drinking between paired short (10-min) time intervals during which light was switched on and off, respectively.…”

“…Russo et al (2017) tested the effect of ALAN at forest drinking sites by comparing drinking between paired short (10-min) time intervals during which light was switched on and off, respectively. In addition, Russo et al (2017) only did their tests in a mountainous region where alternative water sites were available, and they did not test whether a higher motivation to drink induced by water scarcity might make a difference. Therefore, the effects on bat drinking activity recorded during short intervals should also be tested in conditions where lights are kept on uninterruptedly for several hours.…”

“…Second, to account for motivation, we carried out the test both in the same forest area where Russo et al (2017) did their experiment and in a desert region during summer time, when water availability is a limiting factor for wildlife (Korine et al, 2015), and bats might be compelled to drink even at lit sites. First, we tested how bats react to illuminating drinking sites over four continuous hours.…”