The monthly daytime and night-time diet, activity and feeding height of an habituated black lemur group were compared by ‘auditory group sampling’ for a total of 561 daytime hours and 472 night-time hours in Lokobe Forest, Madagascar. Both the daytime and night-time diets were dominated by fruit, but the former was more diverse than the latter and included more leaves. Some food items were eaten mainly or solely at night or during the day. The proportion of total time spent feeding was variable and was lowest between March and June, coinciding with a dearth of ripe fruit. The proportion of night-time spent feeding exceeded the proportion of daytime spent feeding during August, September, October and December. The group fed more frequently in the undercanopy during the day and the canopy during the night. The ratio of time spent feeding to time spent travelling was significantly smaller during the day compared to the night. These differences can be best explained by the group preferring to feed in the undercanopy during the day and the canopy at night.