When Night Becomes Day: Artificial Light at Night Alters Insect Behavior under Semi-Natural Conditions

Abstract

ABSTRACTLight is the most importantZeitgeberfor temporal synchronization in most organisms. Artificial light at night (ALAN) disrupts the natural light-dark rhythmicity and thus negatively affects animal behavior. However, to date, ALAN research has been mostly conducted under laboratory conditions. Here, we used the field cricket,Gryllus bimaculatus, to investigate the effect of ALAN on insect behavior under semi-natural conditions. Male crickets were placed individually in outdoor enclosures and exposed to ALAN conditions ranging from 0 to 1,500 lux intensity. The crickets’ stridulation behavior was recorded for 14 consecutive days and nights and their daily stridulation activity patterns were analysed. ALAN impaired the crickets’ stridulation rhythm, evoking a light-intensity-dependent increase in individual free-run behavior, and in the population’s median activity cycle period. The observed ALAN-intensity-dependent desynchronization occurred despite the crickets’ exposure to almost natural conditions. Our findings reconfirm and further establish the severe impacts of ALAN on animal behavioral patterns.SIGNIFICANCE STATEMENTIn most animals, the rhythmic cycle of day and night serves for timekeeping and for synchronizing daily activity within the individual animal and among the population. Artificial light at night (ALAN) disrupts this natural diurnal cycle. However, our knowledge on the negative impacts of ALAN on insect behavior is still limited. To this end, we exposed adult male crickets to different ALAN intensities under shaded natural lighting and temperature conditions and monitored their stridulation behavior for two consecutive weeks. Despite the semi-natural experimental conditions, our findings reveal ALAN-induced light-intensity-dependent free-run behavior, and thus loss of timekeeping and an ALAN-intensity-dependent desynchronization of the population. This demonstration of anthropogenic effects on animal behavior in natural settings underscores the ecological threats of ALAN.