Variation in Social Structure: the Effects of Sex and Kinship on Social Interactions in Three Lemur Species

The effects of sex and kinship on agonistic and affinitive interactions in Lemur catta, Eulemur fulvus, and Eulemur coronatus were examined to provide information on the social structure of these primates. All adult males and females of three captive forest‐living groups served as focal animals for one year. In contrast to many anthropoid primates, social interactions in these lemurs are characterized by predominantly competitive relations among closely related females, with low overall rates of polyadic conflicts. In L. catta, same‐sexed dyads and pairs of closely related individuals had higher proximity‐corrected frequencies of agonistic interactions than male‐female and non‐kin dyads. Grooming interactions, on the other hand, occurred significantly more often than expected in male‐female pairs and between unrelated animals. The top‐ranking male monopolized the majority of male‐female interactions. In E. fulvus, neither sex nor kinship had significant effects on the distribution of grooming and agonistic interactions. Unlike L. catta, grooming and conflicts were observed in all dyads, resulting in more complex social relationships. Male‐female relationships in E. fulvus were characterized by strong affiliative relations between individual male‐female pairs. Social relationships in E. coronatus were generally similar to those in E. fulvus, except for a significant sex effect on the distribution of interactions, but small sample size precluded a final characterization of this rare species. Collectively, these results suggest that there may be intense competition among individual female lemurs for group membership, even among close relatives in the same matriline. Moreover, interspecific contrasts in male‐male and intersexual relationships indicate fundamentally different male roles in these species. This study revealed that patterns of agonistic and affinitive interactions are not generally predictable from sexual selection theory and interspecific differences in life histories, indicating a need for more quantitative descriptions of social relationships in diverse taxa to identify other ecological and social determinants of social structure.