Abstract
In a rapidly changing landscape highly impacted by anthropogenic activities, the great apes are facing new challenges to coexist with humans. For chimpanzee communities inhabiting encroached territories, not bordered by rival conspecifics but by human agricultural fields, such boundaries are risky areas. To investigate the hypothesis that they use specific strategies for incursions out of the forest into maize fields to prevent the risk of detection by humans guarding their field, we carried out video recordings of chimpanzees at the edge of the forest bordered by a maize plantation in Kibale National Park, Uganda. Contrary to our expectations, large parties are engaged in crop-raids, including vulnerable individuals such as females with clinging infants. More surprisingly chimpanzees were crop-raiding during the night. They also stayed longer in the maize field and presented few signs of vigilance and anxiety during these nocturnal crop-raids. While nocturnal activities of chimpanzees have been reported during full moon periods, this is the first record of frequent and repeated nocturnal activities after twilight, in darkness. Habitat destruction may have promoted behavioural adjustments such as nocturnal exploitation of open croplands.