Diurnal pattern of allogrooming in a group of japanese macaques (macaca fuscata fuscata blyth)

SUMMARY Diurnal variation of allogrooming was studied in a social group of Japanese macaques (Macaca f. fuscata Blyth). Over 150 hr of observation, using the « complete record » sampling method, allowed us to detect a basic diurnal pattern with the highest mean levels in the early afternoon. Such a pattern proved to be fairly uniform under a wide variety of conditions. Statistical analyses showed that only rain and feeding activity influenced it whereas temperature and humidity, in contrast to previous reported studies, failed to prove affective factors. Unlike sex, age affected the daily cycle of allogrooming in that juveniles followed a diurnal pattern different from that of mature individuals. A comprehensive evaluation of these findings suggests that the in-group factors prevail over environmental variables in shaping the diurnal pattern of allogrooming. The nature of such in-group factors (social? physiological?) remains to be investigated.