RELATIONS BETWEEN SEASONAL-CHANGES IN WAT ER METABOLISM, ESTIVATION AND REPRODUCTION IN GERBILLUS-NIGERIAE AND TATERILLUS-PETTERI (RODENTIA, GERBILLIDAE)

Seasonal variations in total body water, body water turnover rates, an d body water balance were determined in wild Gerbillus nigeriae and Ta terillus petteri studied from 1984 to 1991 in the Oursi region (Burkin a Faso). In the 2 sympatric species: (a) body water turnover rates wer e minimum from March to May, maximum from June to October, and medium from November to February; (b) a slight water deficit appeared in Janu ary and February, whereas the water balance was evened out during the rest of the year. With regard to our knowledge on estivation and repro duction in the 2 species, the results suggest that: (1) the reproducti ve offset would result from a decrease in water turnover rates related to dietary changes; (2) the decrease in mobility, characterizing the beginning of estivation would result from a transitory deficit in the water balance which in this case may act as a physiological cue; (3) t he recovery of the water balance during estivation would be necessary for a recovery of the previously demonstrated gonadostimulatory effect of daylength.