Social organization of the Alaotran gentle lemur (Hapalemur griseus alaotrensis)

Knowledge of the social organization of lemurs is still limited for most sp ecies. Where there is sufficient information, it has been shown that lemur social organization differs in essential points from that of other primates . In the field study reported here, demographic structure and life-history processes were investigated in order to characterize the social organizatio n of the Alaotran gentle lemur (Hapalemur griseus alaotrensis). Data were o btained through captures and observations. Alaotran gentle lemurs were foun d in small groups of up to nine individuals. Although most groups contained just one breeding female, a substantial proportion of groups (35%) had two breeding females. Therefore, Alaotran gentle lemurs cannot be classed as b eing organized in monogamous family groups. An extended birth season was fo und, and groups with two breeding females had significantly higher breeding output per adult than groups with a single adult female. Limited data sugg est that females emigrate from their natal group while still subadult, wher eas males can stay in the natal group until they are fully grown and disper se as adults. Variability in group composition, significantly higher reprod uctive output per adult in groups with two breeding females, and delayed di spersal of males suggest that Alaotran gentle lemurs pursue a resource-defe nse mating strategy, rather than a female-defense mating strategy. The sugg estion that extant social lemurs may have evolved from a monogamous system, could explain the differences between lemur social systems and those of ot her primates. (C) 2000 Wiley-Liss,Inc.