Climate, trophic factors, and breeding patterns of the Nile grass rat (Arvicanthis niloticus solatus): a 5-year study in the Sahelian region of Burkina Faso (formerly Upper Volta)

From 1984 to 1989, five populations of the Nile grass rat, Arvicanthis niloticus solatus, living in five different habitats of the Sahelian region were studied in northern Burkina Faso (Oursi, 14°N). The following were investigated: (i) seasonal variations in the percentages of sexually active males and females and the percentage of the population less than 6 weeks old, and (ii) seasonal variations in testis and seminal vesicle masses and plasma testosterone levels in adults. Both the large form of A. niloticus occupying habitats with stable trophic resources and the small form of the species occupying habitats with fluctuating resources showed seasonal breeding, mainly in the dry season, in contrast with what we have observed elsewhere in other species in this region. In dry years with normal rainfall (rains between June and September), breeding occurred from mid-October to mid-July in habitats with constant trophic resources and from mid-October to mid-April in habitats with fluctuating resources. In 19...