Light or flight? The impact of artificial light at night on insect predation risk

Artificial light at night (ALAN) affects over 23% of Earth's land surface, blurring the natural light–dark cycles and celestial cues that animals and plants depend on for orientation and internal timing. This thesis investigates how ALAN contributes to insect declines by altering predator-prey interactions, examining how ALAN impacts predator and prey activities in space and time in relation to anti-predator colouration and behaviours.
Research on three lepidopteran species revealed that under dim light pollution, aposematic caterpillars exposed themselves more on leaf surfaces while cryptic species hid underneath; behavioural shifts that likely affect predation exposure. However, predation experiments revealed no increase in predation rates under ALAN. Despite increased nocturnal activity of great tits under artificial light, predation on cryptic caterpillar larvae did not increase, possibly because light levels were insufficient for efficient foraging. Similarly, community-wide predation on both cryptic and aposematic caterpillar models showed no difference between illuminated and dark forest transects, suggesting that long-term light exposure may diminish the short-term predation increases previously reported. In contrast, jumping spiders extended their nocturnal activity and hunting capability, but only under high-intensity, cold white light, indicating sensitivity to specific light conditions.
In urban settings, dimming streetlights effectively reduced insect attraction and benefited insect populations, though densities remained higher than in dark areas. Pipistrelle bats avoided light and showed no response to light dimming. Automated AI insect detection improved monitoring efficiency for this study, though such methods require careful application depending on light conditions and study objectives.