The specter of predation: The effects of vipers on the foraging behavior of two gerbilline rodents

Predation may have profound effects on individual growth rates, population dynamics, and species interactions via its influence on prey foraging behavior.Here, we examine the response of two gerbil species (Gerbillus allenbyi and G.pyramidum) to greater sand vipers (Cerastes cerastes) and to added illumination (a factor associated with increased risk of predation from owls). We measured gerbil foraging behavior using the number of seed trays (resource patches) foraged and amount of seed resources left in each tray (giving-up densities; GUDs). Fewer seed trays foraged andhigherGUDs indicate a higher perceived risk of predation. 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 activity also caused both species to abandon seed trays at higher GUDs. Overall, gerbils altered their use of resource patches in response to the risk of predation. Comparison to results from previous experiments indicates that the response of the gerbils to predators depends on the nature of the threat posed by the predator.