Shades of gray mouse lemurs: Ontogeny of female dominance and dominance-related behaviors in a nocturnal primate

The ontogeny and establishment of dominance relationships in young individuals have been investigated in various group-living, diurnal primates but respective information is almost entirely lacking for nocturnal, non-gregarious species. As in many other mammals male primates often represent the dominant sex, but the opposite phenomenon (female dominance) is particularly frequent in lemurs, although almost nothing is known about its development. Therefore, we investigated the development of intersexual dominance in parallel to age-related changes in other relevant behaviors in the gray mouse lemur, a solitary forager with female dominance. In particular, the temporal trajectories of social play, marking behavior, social tolerance, and agonistic behaviors were characterized in captive dyads of three different age categories (ACs), among juveniles (ACI: 4-5 months, N = 6), adolescents (ACII: 8-9 months, N = 8) and young adults (ACIII: 12-13 months, N = 8). Data were collected during a series of three encounter experiments between one male and one female per dyad and age category (total observation time: 49.5 hr). Play behavior was observed in all age classes, although the number of playing dyads decreased with increasing age. A significant age-dependent increase in marking behavior was found in females, especially in substrate rubbing and urine washing, but not in males. Although conflict rates did not differ significantly between ACs, females started to win more conflicts from ACII onwards, and social tolerance decreased partly with increasing age. Clear dominance relationships were not observed in ACI and first indications of dominant females were found in ACII with an increasing number in ACIII. This study provides first information about the ontogeny of female dominance in a nocturnal primate and shows that this behavior develops relatively late during ontogeny. In conclusion, this study provides evidence for significant changes in the social lives of maturing mouse lemurs and a rather late social maturation in this species.