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The effects of the illumination of buildings on house-dwelling bats and its conservation consequences

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Abstract

As the illumination of buildings at night increases, light pollution and negative impacts on wildlife also increase. In order to assess the effect of direct lighting on house-dwelling bats, we examined colonies of Rhinolophus ferrumequinum, Myotis emarginatus and M. oxygnathus in illuminated and non-illuminated buildings found in close proximity to each other. We investigated the onset and timing of nocturnal emergence and measured the body mass and the forearm length of juvenile bats. Results show that bright artificial lighting delays the onset or significantly prolongs the duration of emergence and, in the worst cases, may destroy the whole colony. Juveniles are significantly smaller in illuminated buildings than in non-illuminated ones. The differences in length of the forearm and in body mass may suggest that the parturition time starts later and/or the growth rate is lower in bats living in illuminated buildings. Thus, the illumination of buildings could have serious implications for the conservation of house-dwelling bat colonies.
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... Roost illumination has been shown to delay the emergence of narrow-space-foraging bat species (Boldogh et al., 2007;Duvergé et al., 2000;Luo et al., 2021). Some localised studies also suggest that the timing of bat activity might be disrupted at foraging sites due to ALAN. ...
... The delayed timing of activity around light-polluted foraging sites could be explain by several hypotheses. First, bat emergence from roosts might be delayed because of ALAN, as shown by a few studies on narrow-space-foraging species (Boldogh et al., 2007;Duvergé et al., 2000;Luo et al., 2021;McAney & Fairley, 1988). Also, as light pollution is known to decrease landscape connectivity for bats (Hale et al., 2015;Laforge et al., 2019;Stone et al., 2009), a delayed timing of activity at foraging sites could be the result of longer flights to reach them. ...
... However, as light pollution is a constant stressor, delays caused by ALAN may eventually prevent bats from reaching their energetic needs in the medium-and long-terms, which could have cascading effects on individual fitness and population dynamics, and thus result in lower bat abundance at landscape scale when exposed to ALAN. For instance, Boldogh et al. (2007) showed that juveniles of narrow-space-foraging bat species were smaller in illuminated buildings, where bat emergence was delayed because of ALAN. However, our study only focuses on the gestation period and further investigations should be carried out for the lactation onewhen energetic needs are even higherto assess whether ALAN still has an effect on the timing of E. serotinus activity. ...
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... Doren et al., 2017) and has cascade effects on ecosystems (Bennie et al., 2018;Knop et al., 2017). All these ALAN effects are particularly well-known for insectivorous bats (Boldogh et al., 2008;Mathews et al., 2015;Rydell et al., 2017), and ALAN is even proposed as one of the main global threats to bats (Voigt and Kingston, 2016). ...
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... Adverse conditions leads to delayed development and stunted offspring in bats (Meniri et al., 2020;Ransome, 1990) with stunted females (e.g., R. ferrumequinum) having poor survival prospects (Ransome & Hutson, 2000). In Myotis species, juveniles roosting in illuminated buildings had lower body mass than their counterparts in dark roosts, but it was not determined if this reduced their survival rate (Boldogh et al., 2007). The influence of anthropogenic stressors on TL could be achieved by exploring TL differences between populations of the same species (e.g., urban vs. rural) and/or manipulation of different stressors (e.g., exposure ...
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