The effect of rainfall on population dynamics in Sahara-Sahel rodents

In arid and semi-arid regions, rainfall is scarce, limiting primary productivity and animal reproduction. As long-term population monitoring is limited in remote arid areas, indirect and remote technicals are needed. We investigated if and how populations of rodents in Sahara-Sahel responded to past events of rainfall. Using short field surveys and remotely sensed rainfall data, spanning between years 2010 to 2015, we tested if rainfall prior to field surveys affected populations of Gerbillus rodents. Generalized additive analysis showed that amount of moonlight (the effect of number of days away from full moon) negatively correlated with number of trapped animals. When controlling for moonlight and geographic and temporal variation, rainfall up to 1 year prior to surveys positively and rainfall 2 years prior to surveys negatively correlated with number of trapped gerbils. We suggest that the effect of increased number of gerbils resulted from reproduction and population density increase after bursts of primary productivity. Negative correlation with rainfall could be related to increased predation or other ecological effects (e.g., resource collapse, pathogens spread) on prey population densities and activity levels. Our results suggest multiphase delayed effect of gerbils population response to rainfall implying interactive model of population regulation in rodent communities on Sahara-Sahel. Presented indirect method and results are readily applicable to population monitoring and management of remote and understudied areas.