Rates of Agonism by Diurnal Lemuroids: Implications for Female Social Relationships

Sterck and colleagues (Behaviour 134:749-774, 1997) focused attention on the evolutionary ecology of female social relationships within and between groups and proposed a model that distinguishes 4 categories of female relationships, which correspond to particular types of intra- and intergroup competition. They emphasized literature on haplorhines in their model because of numerous, detailed studies conducted on a range of species in the wild; in contrast, strepsirrhines such as the lemuroids are poorly represented. We evaluate more closely their classification of lemuroids as Dispersal-Egalitarian using a greater number of species of Lemur, Eulemur, Varecia, Hapalemur, Indri, and Propithecus. For the focal species we found that female philopatry occurs rarely, agonistic rates are relatively low, female dominance hierarchies are not stable and do not exist year-round, and intra- and intergroup female-female competition is infrequent. Therefore, our results support the suggestion that a majority of lemuroid taxa we surveyed correspond to the Dispersal-Egalitarian category with 2 probable exceptions: Lemur catta and Propithecus edwardsi. Because female Lemur catta are philopatric, have year-round dominance hierarchies with female matrilines, exhibit the highest rates of agonism in studied lemuroids, and have frequent intra- and intergroup female-female competition, it would seem that they more closely correspond to the category Resident-Nepotistic. However, maternal Lemur catta rarely support their offspring in agonistic contests and matrilineal rank is not inherited, which leads us to state that the species does not fit into any existing category that explains the nature of female social relationships. The relationships of female Propithecus edwardsi are also a challenge to categorize under the current model because some of their characteristics -typical female dispersal and low agonistic rates- fall into the Dispersal-Egalitarian category, yet other behaviors -intense targeted aggression and stable and year-round female dominance hierarchies- do not.