Rodent's Foraging Behavior in Coastal Dunes

Predation risk in prey can be more important to an ecosystem than a direct kill by a predator. It can influence the behavioral choice of whether to feed on a food patch and risk being eaten or forgo that feeding opportunity as a safety trade-off. This optimal foraging phenomena can be measured using giving-up densities (GUD). GUDs measure the amount of food left over in a food patch once the prey stops foraging. GUD trays will be placed in the coastal dunes of the Humboldt Bay National Wildlife Refuge in Arcata, CA between June and August. In this experiment, we will determine if GUDs of rodents differ where European Beachgrass, Ammophila arenaria is present and absent. Rodents are predominant seed foragers in this ecosystem, understanding their foraging habitat selection has important conservation implications. The trays will consist of a container filled with 1.0 L of sand with 10.0 g of sunflower seeds. Two grids of 25 trays each spaced 5 m apart will be placed where A. arenaria is present and absent. Trays will be checked at sunrise and sunset providing nocturnal and diurnal GUDs. This will be replicated for six days in up to four study sites within the dunes. We hypothesize that GUDs will be higher in the absence of A. arenaria because of the predation risk it presents of being detected by a predator in an open habitat. This information can help to better understand predation risk and foraging behavior of rodents in a coastal dune system.