International audience The composition, structure, and reproductive phenology of a community of murid rodents were investigated for 1 year at two sites in an undisturbed forest in southwestern Gabon, Africa. We captured 1531 mice belonging to 11 species and eight genera. At both sites, species richness varied seasonally and tended to be maximal during the period of maximal trap success. For the most abundant species (Hylomyscus stella, Hybomys univittatus, Heimyscus fumosus, and Praomys cf. misonnei), a general unimodal trend in trap success was detected, owing to variations in breeding activity and survival, with a minimum around the long rainy season and a maximum either during the short rainy season or at the beginning of the following long dry season. These fluctuations varied in magnitude among species, and seasonal variations in relative abundance were recorded. Our results support the assumption that in the tropics, rainfall and associated patterns of fruit and insect abundance are important factors which may act directly or indirectly to initiate breeding activity so that lactation occurs at a time of greatest food abundance. Finally, intrapopulational differences in age at sexual maturity were found, both between the sexes and among individuals of the same sex.