Some exceptions have investigated these impacts in the field in habitats that are naturally dark and lit for experimental purposes ( Stone et al., 2009 Minnaar et al., 2014 Bailey et al., 2019) or areas that experience temporary lighting depending on human activities, e.g., at stadiums ( Schoeman, 2015).
Many studies have focused on the impacts of noise and light individually on bat behaviour, predominantly in a laboratory setting, focusing on a single or select few species. For example, bats that benefit from foraging around artificial light sources have shown higher blood metabolite levels (ß-hydroxybutyrate) early in the evening compared to species that do not forage around lights ( Cravens and Boyles, 2019). Combined, these aspects governing responses of bats to alterations in their environment could result in physiological changes.
It is generally accepted that bats exhibit trait-based responses to these habitat-specific environmental changes based on morphology, such as differences in wing shape and associated echolocation call ( Aldridge and Rautenbach, 1987 Schoeman, 2015 Jung and Threlfall, 2018), as well as sensitivities of audiological and visual systems ( Schaub et al., 2008 Eklöf et al., 2014 Luo et al., 2015 Haddock et al., 2019 Finch et al., 2020), and by shifts in behaviour and community structure due to differential roosting and feeding preferences of different foraging groups: open air, clutter edge, and clutter ( Norberg and Rayner, 1987 Bader et al., 2015 Monadjem et al., 2020). Opencast mining allows the study of the effects of habitat degradation due to the physical removal of natural habitat and continual noise and nighttime light pollution. Our study highlights the importance of vegetation cover and the complexity of the interaction between bats and the environment incorporating anthropogenic factors (artificial lighting, continuous noise, and habitat degradation) and natural factors such as minimum temperature, moon phase, and season that confound trends in bat species richness and responses in relation to opencast mining.Īnthropogenic developments expose bats to habitat alterations and a range of pollutants, to which bats are known to be sensitive ( Jones et al., 2009 Naidoo et al., 2016 Frick et al., 2019). Anthropogenic noise had no significant impact on bat activity and species richness. Artificial light only significantly affected feeding activity with less feeding activity in the lit areas. In general, bat activity of both open-air and clutter-edge foragers was negatively impacted over areas close to mining operations that were devoid of vegetation cover.
Mixed-effect models revealed that natural vegetation was the most important factor impacting species richness and overall bat activity. Clutter-feeding bats were virtually absent compared to surrounding natural habitats, suggesting the negative impact of vegetation removal and/or light and/or noise pollution. The impact of natural vegetation cover, artificial light intensity and noise (dBA) were investigated on the bat community on the opencast Venetia diamond mine using mixed-effects models.
#Bat auditory sensitivity free
2Afromontane Unit, Department of Zoology and Entomology, University of the Free State, Phuthaditjhaba, South Africaīats are known to be sensitive to changes in their environment.1Department of Zoology, School of Natural and Mathematical Sciences, University of Venda, Thohoyandou, South Africa.
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