Genetic determination of paternity in captive grey mouse lemurs: Pre-copulatory sexual competition rather than sperm competition in a nocturnal prosimian?

Among nocturnal Malagasy prosimians, the grey mouse lemur (Microcebus murin us) is considered as a solitary species having a promiscuous mating system, Indirect evidence, such as the lack of sexual dimorphism, the high relativ e testes size of males and the high synchronism in oestrus occurrence among females. supports the presence of a sperm-based scramble competition. In c aptive animals, we used genetic determination of paternity to define the re lationship between mating success and reproductive success of males kept in a group with several females during the mating period. Within each group, an intense sexual competition arose among males for priority of access to o estrous females. High ranking males, as deduced from the direction of agoni stic interactions displayed a significantly higher frequency of marking beh aviours, chemosensory investigations of females, and sexual behaviours. A r obust relationship was found between male rank and reproductive success sin ce 16 out of the 17 litters (35 young) produced. have been sired by the hig hest ranked male of the group. Moreover, the finding that female aggression was related to both male sexual solicitations and to male rank, suggests t hat females could exert a choice. Under specific captive conditions, grey m ouse lemurs, showing all traits of post-copulatory sperm-based scramble com petition, exhibit a mating system relying on pre-copulatory aggression-base d competition. Olfactory signals rather than morphological traits might he used. in this nocturnal primate. for both sexual co-ordination between sexe s and partner choice.