Abstract
Differences in natural light conditions caused by changes in moonlight are known to affect perceived predation risk in many nocturnal prey species. As artificial light at night (ALAN) is steadily increasing in space and intensity, it has the potential to change movement and foraging behavior of many species as it might increase perceived predation risk and mask natural light cycles. We investigated if partial nighttime illumination leads to changes in foraging behavior during the night and the subsequent day in a small mammal and whether these changes are related to animal personalities. We subjected bank voles to partial nighttime illumination in a foraging landscape under laboratory conditions and in large grassland enclosures under near natural conditions. We measured giving-up density of food in illuminated and dark artificial seed patches and video recorded the movement of animals. While animals reduced number of visits to illuminated seed patches at night, they increased visits to these patches at the following day compared to dark seed patches. Overall, bold individuals had lower giving-up densities than shy individuals but this difference increased at day in formerly illuminated seed patches. Small mammals thus showed carry-over effects on daytime foraging behavior due to ALAN, i.e., nocturnal illumination has the potential to affect intra- and interspecific interactions during both night and day with possible changes in personality structure within populations and altered predator-prey dynamics.
Highlights
When animals show foraging behavior, they constantly have to face the trade-off between acquiring food and avoiding predation (Sih, 1980; Lima and Dill, 1990)
In a previous study we found that bank voles reduced their home ranges in outdoor enclosures under relatively homogeneous nighttime illumination (Hoffmann et al, 2018) but could not determine if this was due to voles opportunistically exploiting food resources from insect attraction to lighting or if it was due to reduced activity through perceived predation risk
Time in trays – sum of time spent in trays per side of arena, N Visits in trays – number of visits in seed trays per side of arena, variation in giving-up densities (GUDs) – difference in giving-up density between the two seed trays on either side of the arena, treatment – light treatment, latency body – latency to leave the nest box for the first time, Rm – marginal R2 value based on fixed factors, Rc – conditional R2 value based on fixed and random factors, df – degrees of freedom
Summary
When animals show foraging behavior, they constantly have to face the trade-off between acquiring food and avoiding predation (Sih, 1980; Lima and Dill, 1990). Animals often reduce foraging activity itself (Daly et al, 1992; Kotler et al, 2010) or shift their activity toward safer habitats with a higher amount of cover (Bowers, 1988; Perea et al, 2011) This shows that higher levels of nighttime illumination lead to an increase in the perceived predation risk in many species, especially in small mammals. In a previous study we found that bank voles reduced their home ranges in outdoor enclosures under relatively homogeneous nighttime illumination (Hoffmann et al, 2018) but could not determine if this was due to voles opportunistically exploiting food resources from insect attraction to lighting or if it was due to reduced activity through perceived predation risk.
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