The influence of snakes on the foraging behavior of gerbils

Examined the response of Gerbillus allenbyi and G. pyramidum to the presence of the desert diadema snake Spalerosophus diadema, and to added illumination (a factor associated with increased risk of predation from owls). Fewer seed trays foraged and higher giving-up densities (GUDs) are indicative of higher perceived predatory risk. Both species foraged fewer seed trays in response to illumination, and G. pyramidum foraged fewer trays in the bush microhabitat. In response to the presence of snakes, G. pyramidum foraged fewer resource patches in the absence of added illumination. Overall, this species preferred the open microhabitat and may have intensified its use of the open in the presence of snakes. G. allenbyi intensified its use of the bush microhabitat in the presence of added illumination. Both gerbil species left resource patches at a higher GUD in response to illumination and to snakes. While the GUD of G. allenbyi did not differ between microhabitats, G. pyramidum had a higher GUD in the bush than open microhabitat. Predator facilitation is a higher order interaction in which the presence of one predator species makes it easier for another predator to capture prey. Results support the hypothesis that owls exert a greater risk in the open microhabitat, and snakes may pose a greater threat in the bush microhabitat. -from Authors