FORAGING SUBSTRATE AND ESCAPE SUBSTRATE: PATCH USE BY THREE SPECIES OF GERBILS

Abstract

The three Negev Desert gerbils, Gerbillus pyramidum (greater Egyptian sand gerbil), Gerbillus allenbyi (Allenby's gerbil), and Gerbillus dasyurus (Wagner's gerbil), show strong patterns of habitat selection along a gradient, from sandy to loessal to rocky habitats, respectively. Within a habitat, a gerbil must be able to harvest seeds and escape predators. To test for the habitat-specific processes governing habitat partitioning by gerbil species, we investigated the roles of escape substrate and foraging substrate in affecting patch use. In an aviary, we manipulated predatory risk using artificial illumination and the presence of Barn Owls (Tyto alba). We manipulated escape substrate and foraging substrate by creating habitat and food patches of sand, rock (a mix of sand and small rocks), and loess substrate. In response to owls, all three gerbil species foraged less and increased their giving-up densities (GUDs) in food patches. In response to foraging substrate, all three species had their lowest GUDs ...