We investigated the vocal repertoire of a Malagasy primate: the black lemur (Eulemur macaco macaco). The first study allowed the characterization of 16 different vocal signals on the basis of acoustic parameters. Black lemurs emit sparse harmonic sounds, dense harmonic sounds, spectrally structured noise (Beeman, 1998) and a wide variety of grunts. The second study focused on the behavioral context of emission of these signals and used the pre- and post-event histogram method (Douglass and Sudd, 1980; Preuschoft, 1995a). It provides statistical demonstration of the association between a signal and other behaviors of the emitter, thus giving insight into the latter’s motivations. Four signals are linked to affiliative and agonistic interactions. Three signals express a state of alarm, and two appear related to discomfort. Most grunts are linked to contact and signal precisely the emitter’s level of vigilance. Other interdisciplinary communication studies could benefit from methodology and software used here.

Although the brown lemur (Eulemur fulvus) and the black lemur (Eulemur macaco) share many life parameters and are genetically closed, they show considerable difference in social organization. Dominance relationships with no systematic effect of gender characterize the former, whereas the latter is based on female dominance. The present study was done on two captive groups of brown lemurs and one semi-free-ranging group of black lemurs. To reveal links between the specific pattern of social organization and agonistic behaviors, agonistic interactions were analyzed for each species as for their context of occurrence, symmetry, initiation, and outcome. The effect of gender in the initiation of conflicts appeared as the only notable interspecific difference, aggression being mostly initiated by females in E. macaco and by males in E. fulvus. Conflict outcome was generally in favor of the initiator, regardless of gender in both species. The analysis of postconflict behaviors revealed conciliatory processes in the brown lemur, whereas reconciliation seemed to be absent in the black lemur, a characteristic shared with the ring-tailed lemur (Lemur catta), another lemur species with female dominance. Aggr. Behav. 28:62-74, 2002.

Third-party interventions in conflicts have revealed complexity in primate social relationships. This type of intervention has seldom been analyzed in prosimians, although many of these species exhibit complex (multimale/multifemale) social organizations. The present study on captive brown lemurs (Eulemur fulvus fulvus) shows that dominant individuals were more likely to intervene in conflicts. Both males and females intervened aggressively in conflicts. Female aggressive interventions occurred mainly on behalf of close kin, whereas males mainly intervened on behalf of juveniles. This study also provides the first record of neutral or peaceful interventions in lemurs. Although females intervened neutrally, almost all neutral interventions were by dominant males. Dominant males intervened in conflicts neutrally more often than aggressively, principally in conflicts between adults and juveniles or between juveniles. Neutral interventions by males always ended the conflicts and were often followed by affiliative contacts between participants (intervenors and opponents). In lemurs, female interventions can be explained by kin selection, while the nature of dominant males' interventions suggests a control role. Interventions by males on behalf of juveniles may increase the formers' fitness.

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