RELATION OF INTERGROUP VARIATION IN ALLOGROOMING TO GROUP SOCIAL-STRUCTURE AND ECTOPARASITE LOADS IN RED HOWLERS (ALOUATTA-SENICULUS)

We compare the allogrooming behavior of 5 troops (average size = 8.2) of red howlers (Alouatta seniculus) from the Venezuelan Llanos with th at of other A. seniculus and Alouatta spp. of the genus. lit 126.9 obs ervation hr, we recorded 118 allogrooming events, with an average bout length of 109 sec. Females groomed more frequently than males did, bu t as groomees there is no significant differences between sexes. Adult males groomed adult females mostly in a sexual context (before copula tion). Allogrooming rates differ significantly among groups. There are also significant differences among members of the same troop both as groomers and groomees, which we explain in the context of the social b ehavior and history of each troop. There is no significant correlation between weight of the groomee and duration of the grooming bout. Howe ver, the examination of grooming rates and ectoparasite load suggests that allogrooming may have hygienic consequences. Differences in allog rooming rates among species of Alouatta are related to differences in group kin structure and patterns of female competition in particular c oalition formation. We conclude that the social structure and the degr ee of relatedness among individuals within a group (or among individua ls in a population in interpopulation comparisons) is a more important determinant of allogrooming rate than body size or group size. Our re sults emphasize the importance of considering intergroup and interpopu lational variation in behavior.