WATER REDISTRIBUTION AND THE LIFE-CYCLE OF SAHELIAN RODENTS

In the North of Burkina Faso (Oursi: 14 degrees 20'-14 degrees 50'N/0 degrees 10'-0 degrees 40'W), in Mastomys huberti and Arvicanthis nilot icus which experience a rich diet all year round in unrestricted habit ats, water metabolism is constantly high, reproduction is continuous a nd animals are sedentary throughout the year (only A. niloticus shows a short sexual rest period induced by some nontrophic factors: dayleng th and temperature). In A. niloticus which experience a constantly ric h diet, but face an annual flooding period (in flooding habitats), ann ual dispersion and sexual rest phases are induced by some non-trophic factors: daylength, temperature and air humidity. In Taterillus gracil is and Mastomys erythroleucus which experience an annual rich-food per iod twice as long as the annual poor-food period (in semi-arid habitat s), the annual dispersion and sexual rest phases are both related to a reduction in water metabolism, while the annual sedentarization and b reeding phases are both related to an increase in water metabolism. Tn Gerbillus nigeriae which experience an annual poor-food period twice as long as the annual rich-food period (in arid habitats), the annual dispersion and sexual rest phases are both related to a reduction of w ater metabolism, but the annual sedentarisation and breeding phases ar e both induced by non-trophic factors (mainly daylength).