Reproductive patterns in the Baluchistan gerbil, Gerbillus nanus (Rodentia: Muridae), from western Saudi Arabia : the role of rainfall and temperature

There is little information pertaining to the reproductive biology of the Baluchistan gerbil (Gerbillus nanus) despite a broad distribution throughout the Middle East. In the current study, body mass, reproductive–tract morphometrics plus gonadal histology and endocrine profiles of males and females were studied over 12 consecutive months in a field population of Baluchistan gerbils from the western region of Saudi Arabia in an attempt to gain insights into a) the environmental zeitgeber(s) that correlate with reproduction as well as b) to assess if reproduction is seasonal or aseasonal in this species. With the exception of testosterone all male reproductive indicators varied seasonally and were lower during winter than the rest of the year and most increased with rainfall. In contrast, ovarian mass and volume as well as immature follicle counts showed no seasonal patterns and were independent of rainfall or temperature. First pregnancies were observed in late spring coinciding with the increased progesterone concentrations and peaked in summer. This was accompanied by seasonal peaks in the number of Graafian follicles and corpora lutea in females and these parameters were significantly correlated with temperature, but not rainfall In the Arabian Peninsula male, but not female Baluchistan gerbils show seasonal recrudescence and this appears to be correlated largely to rainfall.