Impact of artificial light at night on the distribution and behaviour of nocturnal micromammals.

Details

Supervisors

Pierre Bize ; Hans Van Dyck

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

Natural light cycles allow living organisms to synchronise their behaviour and physiology with their environment. However, the frequent use of artificial light at night (ALAN) for human activities alters the perception of these natural cycles. Living organisms are therefore affected in many ways by this human-induced rapid environmental change (HIREC). From bacteria to mammals, but also plants, crustaceans, fish, birds, insects, or amphibians: most forms of life are known to be disturbed by ALAN. As they are mostly nocturnal, mammals are relevant models to study light pollution at night. In particular, small mammals are useful study models due to their small size and high diversity. According to a growing body of research, ALAN can alter many behaviours in small mammals, such as foraging or exploratory behaviour, or physiological processes, such as melatonin production. ALAN may therefore mask the natural light cycles of small mammals or increase their perceived risk of predation. However, some of the underlying mechanisms of these changes remain unclear. In this project, I investigated the effects of ALAN using an observational approach where I assessed the activity density of small mammals using track plates laid down in lit and unlit meadows. I also used an experimental approach where light poles were installed in fallows to create lit and unlit fallows. I also investigated the effects of ALAN on taxon composition and individual characteristics by capturing small mammal in these experimental fallows using longworth traps. Finally, the trapped individuals were also used in an openfield experiment where I investigated the effects of ALAN on the risk-taking score and activity level of small mammals. My study of the effects of ALAN on the presence and activity density of micromammals in experimentally lit fallows and correlated data in meadows suggests that, although micromammals are as likely to be found in lit and unlit areas, ALAN is nevertheless modifying their behaviours, with micromammals being less active in lit areas. The trapping experiment showed that the three different trapped taxa (voles (Microtus sp), mice (Apodemus sp) and shrews (Crocidura sp)) did not respond differently to ALAN and that ALAN had no influence on their body mass. Follow-up behavioral analyses of Microtus in openfield showed that although Microtus individuals showed similar levels of activity and risk-taking regardless of their origin, individuals from lit fallows were more cautious when the light was on, in particular by limiting their activity and risk-taking, reflecting a tendency towards greater behavioural plasticity.