The effects of age and sex on interest toward movies of conspecifics in Japanese macaques (Macaca fuscata).

Previous studies have suggested that images of conspecifics are useful for environmental enrichment for nonhuman primates, but whether the age and sex of the animals alter the effectiveness of such images is unclear. We investigated preferences to movies in Japanese macaques (Macaca fuscata; male and female; age, 2 to 19 y). Each monkey was housed individually in a cage outfitted with a touch-sensitive computer display. A subject monkey that touched the display was shown 1 of 30 movies that were recorded at an open enclosure containing their conspecifics. During the experimental sessions, 25 of 38 subjects touched the display at least once. The response duration was longer when monkeys appeared in the movies. The response duration decreased with age in male monkeys but not female monkeys. The results suggested the movies of conspecifics are useful for environmental enrichment, but further consideration seems appropriate for various subpopulations, particularly aged monkeys.