Seasonal changes in the population dynamics of hairy-footed gerbils in theNamib Desert

The dynamics and demography of gerbil populations at three study sites in t he Namib Desert dunefields are reported. Low and fluctuating rodent biomass resulted from low primary and insect productivity caused by extremely low levels of precipitation. Reproduction was strictly seasonal and temporally associated with the occurrence of seeds in the diet. However, although seed s likely triggered reproduction, they did not sustain breeding. The gerbils were primarily insectivorous but also consumed some green plant material. Insects supply the protein, and plant tissues the vitamins and minerals, ne cessary for the maintenance of reproduction. Precipitation drove the system , regulated primary production, and hence determined gerbil population dyna mics; plane of nutrition or a reproductive trigger initiated breeding, but requires experimentation. Juvenile recruitment was postponed, despite an ap parent sufficiency of food resources during reproduction, and was likely in hibited by reproduction-related aggression of adults. Extrinsic and intrins ic factors are implicated in controlling the demographic processes of gerbi ls in the Namib Desert dunefields.