PREDATION RISK AND COMPETITION AFFECT HABITAT SELECTION AND ACTIVITY OF NAMIB DESERT GERBILS

Microhabitat partitioning based on microhabitat-specific predation rat es has been well documented as a mechanism of coexistence in desert ro dents. In the Namib Desert, two species of rodent, a nocturnal dune ha iry-footed gerbil, Gerbillurus tytonis, and a diurnal striped mouse, R habdomys pumilio, co-occur in a vegetated island in the dune sea. The species show a marked preference for the same microhabitat, although g erbils also inhabit a second microhabitat where predation risk is grea ter. We provide direct experimental evidence for the role of predation risk and both inter- and intraspecific competition in affecting forag ing behavior and habitat selection of gerbils. Using two techniques (t racking and seed trays), we were able to show that gerbils decrease fo raging activity in vegetated areas during periods of increased illumin ation (full-moon periods). Removal of a potential competitor, the stri ped mouse, as well as removal of conspecifics, resulted in a significa nt increase in gerbil foraging activity. We propose that high suscepti bility to predation results in a shared preference for the safest habi tat and leads to competition for limited resources.