This paper analyzed seasonal and diurnal differences in feeding, locom
otion, inactivity, and social grooming of adult and subadult free-rang
ing vervet monkeys in Natal (38 degrees 35'S and 31 degrees 46'E). Bre
aking down hourly activity budgets from the perspective of reproductiv
e seasons (birth, premating, and mating seasons) which correspond to e
nvironmental conditions in Natal, ive obtained several results. First,
there were diurnal Variations for all the behaviours in all seasons s
tudied, except for inactivity during the mating season when days were
shorter and there was greater food shortage and sexual competition. Se
cond, the seasonal influence on the hourly periods of increased activi
ty could not be explained solely by the photoperiod or by the other cl
imatic factors analyzed. Finally, over-all seasonal differences in act
ivity were mainly reflected by the hourly distribution of feeding in t
he morning and the pattern of inactivity throughout the day. Therefore
, rhythms in activity should be understood in terms of adaptation to b
oth climatic constraints and other unrelated metabolic requirements.