Artificial light at night makes guppies more courageous during the day, according to a behavioural study led by researchers from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Max Planck Institute for Human Development. Exposing fish to artificial light at night made fish more active during the night, and also made them emerge quicker from hiding places during the day, which could increase their exposure to predators. Nocturnal lighting, however, did not affect their swimming speed or social behaviour during the day.