Illuminance preferences of nocturnal primates

Abstract

Laboratory tests reveal a preference for illuminances in a broad range of night light by individuals belonging to four species of nocturnal primates (Aotus trivirgatus, Galago crassicaudatus, Galago senegalensis, andNycticebus coucang). In volitional tests the animals altered the light level very frequently, in one case as often as every 7 sec. In these tests the animals tended to avoid total darkness and extremely dim light as well as moderately bright light. These avoided levels, particularly extremely dim light and darkness, inhibited locomotor activity. The greater bush babies preferred dimmer light for manipulative activities than for locomotion. Nocturnal primates differ from nocturnal rodents in being much more highly motivated to seek variety and frequent stimulus change when in deprivation conditions, and in their avoiding and being markedly inhibited by darkness.