Diurnal and seasonal variations in vervet monkeys' activity

This paper analyzed seasonal and diurnal differences in feeding, locomotion, inactivity, and social grooming of adult and subadult free-ranging vervet monkeys in Natal (38 degrees 35'S and 31 degrees 46'E). Breaking down hourly activity budgets from the perspective of reproductive seasons (birth, premating, and mating seasons) which correspond to environmental conditions in Natal, we obtained several results. First, there were diurnal variations for all the behaviours in all seasons studied, except for inactivity during the mating season when days were shorter and there was greater food shortage and sexual competition. Second, the seasonal influence on the hourly periods of increased activity could not be explained solely by the photoperiod or by the other climatic factors analyzed. Finally, over-all seasonal differences in activity were mainly reflected by the hourly distribution of feeding in the morning and the pattern of inactivity throughout the day. Therefore, rhythms in activity should be understood in terms of adaptation to both climatic constraints and other unrelated metabolic requirements.