Although nonhuman primates have highly developed visual cognitive abilities, they have few opportunities to exert such abilities in captivity. Video presentation can reproduce multiple features of the complex real visual world. Therefore, video presentation can be expected to act as environmental enrichment for captive primates. The present study evaluated the enriching effects of novelty and content of videos as well as control over videos using newly developed technology including network-shared YouTube videos and an infrared distance sensor. Baseline data were obtained for 10 days without video display and then 10 days with the display showing no videos in four individually housed monkeys and six pair-housed monkeys. The monkeys were then exposed to videos of conspecifics, people, and animation and observed for 30 days. In some days, the monkeys had control over videos such that videos played only when subjects sat directly in front of the display. Observations were then taken for an additional 10 days with no videos. Behaviors such as time watching videos, abnormal behavior, and time spent in front of display were recorded for 60 min per day using instantaneous sampling with a 30-s interval. Monkeys displayed fewer abnormal behaviors when the video was playing (individually housed: 11.3 sampling points, pair-housed: 7.7 sampling points) than when the video was not playing (individual housed: 22.5 sampling points, pair-housed: 10.8 sampling points) (P < 0.001). The abnormal behaviour over the course of the observation days Video system enrichment for Japanese macaques 3 showed no evidence of habituation to videos. The frequency of watching the videos and abnormal behaviour differed depending on the presented contents of videos (P < 0.001). The subjects spent more time in front of the display in the days in which they could control the videos (individually housed: 89.1 sampling points, pair-housed: 17.6 sampling points) than in those in which they had no control (individually housed: 70.1 sampling points, pair-housed: 7.3 sampling points) (P < 0.001), suggesting that they were preferentially choosing to watch the videos. These results suggest that video presentation can be a useful technique to decrease abnormal behaviour of captive Japanese macaques. The content and controllability over videos were influential on their behaviour, suggesting that implementation of video enrichment that includes conspecifics videos and controllability over videos can improve animal welfare. Implementation based on an understanding of species-specific characteristics can contribute to effective environmental enrichment.

Contrafreeloading, which means that animals work for food even though identical food is freely available, has been reported in animals' feeding behavior. This phenomenon has been assumed to be explained by the information primacy model, in which the information about a food resource as well as the food itself is valuable for animals. This study confirmed a contrafreeloading-like phenomenon using movies as rewards rather than food in Japanese macaques (Macaca fuscata) and investigated the motivational system that exists behind contrafreeloading. In the experiment, movies that were presented dependently on subjects' responses (earned movies) and movies that were presented automatically (free movies) were supplied simultaneously. The subjects continued to make responses to obtain the presentation of the earned movies although identical movies were available as free movies. These results provide the first evidence of contrafreeloading that occurs with movie rewards. The motivation maintaining the contrafreeloading behavior for movies may be control over the environment according to the competence theory.

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