Martine Perret Département d'Ecologie et gestion de la Biodiversité, Muséum National d'Histoire Naturelle, Brunoy, F Title Olfactory communication in mouse lemurs: mechanisms and sociobiological consequences Abstract The gray mouse lemur, a Malagasy prosimian, exhibits particular life history traits that represent adaptive responses to seasonal environmental constraints. Large variations in spatial distribution, density and degree of home-range overlap within and between the sexes have been depicted suggesting a high plasticity of social responses to ecological constraints. All biological rhythms studied so far demonstrate high seasonal changes primarily entrained by photoperiodic variations but modulated by social communications that, in this nocturnal species, mainly rely on chemical signals. Reproductive and energy balance strategies represent two main examples of functional interactions between environmental conditions and social signals. In mouse lemurs, reproductive strategies are based on scramble competition polygyny, sperm competition, temporary mate guarding and possibly female choice. Chemical signals enhance sexual coordination between sexes but have also clear effect on individual reproductive fitness within sexes. These effects go through pheromonal modulation of sexual hormones leading to changes in sexual efficiency of males and in offspring production of females. Chemical signals interfere also on seasonal fluctuations of body mass especially on the autumnal fattening reducing individual survival during the winter season. More, energy saving strategies, within which the capacity to enter daily torpor is crucial for survival, are adjusted to local conditions including social sleeping associations. Lastly, mechanisms linking sensory information and metabolic/hormonal responses rely on neural pathways connecting sensory processes to biological clocks. In conclusion, social interactions that depend on population density have dominant modulator effects on population dynamics, through individual physiological responses, explaining in part the diversity of wild mouse lemurs populations.   CV 1971 - Ph.D. in Biology (speciality Endocrinology), University of Paris VI. 1980 - Doctor es Science (speciality Endocrinology), University of Paris XI. 1972 - 1974 - Research position, CNRS. 1974 - 1982 - Research assistant, CNRS - Studies on Prosimian biology (CNRS-MNHN ERA 0410) 1982 - 1990 - Assistant professor, CNRS - Adaptive mechanisms in mammals (CNRS-MNHN 1183). 1990 - 2006 - Professor, CNRS Head of Ecophysiological studies unit Manager of the breeding colony of primates in Brunoy Head of the laboratory «Functionment, Evolution and adaptive strategies of tropical Ecosystems" (CNRS-MNHN 5176). Selected recent publications: Perret M 2005 - Relationship between urinary estrogen levels before conception and sex ratio at birth in a primate, the gray mouse lemur. Human Reproduction, 20: 1504-1510. Aujard F, Schilling A & M Perret 2005 - Gonadotrophin-releasing hormone (GnRH) immunoreactive neurons in male mouse lemurs following removal of the vomeronasal organ. Brain Research, 1043:247-250. Génin F, Schilling A & M Perret 2005 - Social inhibition of seasonal fattening in wild and captive gray mouse lemurs. Physiology and Behavior, 86:185-194. Séguy M & M Perret 2005 - Factors affecting the daily rhythm of body temperature of captive mouse lemurs. Journal of Comparative Physiology B, 175(2):107-115. Institution address: Dr Martine Perret Département d'Ecologie et gestion de la Biodiversité Muséum National d'Histoire Naturelle UMR CNRS-MNHN 5176 4 avenue du petit château F - 91800 Brunoy martine.perret@wanadoo.fr