THE SPECTER OF PREDATION - THE EFFECTS OF VIPERS ON THE FORAGING BEHAVIOR OF 2 GERBILLINE RODENTS

Predation may have profound effects on individual growth rates, popula tion dynamics, and species interactions via its influence on prey fora ging behavior. Here, we examine the response of two gerbil species (Ge rbillus allenbyi and G. pyramidum) to greater sand vipers (Cerastes ce rastes) and to added illumination (a factor associated with increased risk of predation from owls). We measured gerbil foraging behavior usi ng the number of seed trays (resource patches) foraged and amount of s eed resources left in each tray (giving-up densities; GUDs). Fewer see d trays foraged and higher GUDs indicate a higher perceived risk of pr edation. Accordingly, G. allenbyi foraged fewer seed trays in response to illumination and in the open microhabitat. In addition, vipers may have affected foraging activity in both gerbil species and caused G. pyramidum to forage in fewer trays in the bush microhabitat Viper acti vity also caused both species to abandon seed trays at higher GUDs. Ov erall, gerbils altered their use of resource patches in response to th e risk of predation. Comparison to results from previous experiments i ndicates that the response of the gerbils to predators depends on the nature of the threat posed by the predator.