THE WORK COSTS OF EARNING FOOD AS A DETERMINANT OF PATCH LEAVING

Foraging theorists have long emphasized the role of the energy (work) costs of food items on foraging behavior. However, few experiments hav e measured this variable or demonstrated that animals are indeed sensi tive to work costs. Experiment 1 assessed whether rats (Long-Evans) ca n use the work costs of food to determine whether a food patch is exha usted. Rats performed a fixed amount of work for each food item (fixed -work [FW] schedule), but food was withheld unpredictably to simulate sudden patch depletion. It was found that rats left patches only when the work costs of unsuccessful searches (giving-up work) exceeded the prevailing work costs of food. The time and response costs of unsucces sful food searches (giving-up time and giving-up responses) were not p redictive of patch leaving. Experiment 2 showed how rats regulated wor k in this paradigm by examining the role of exteroceptive stimuli conn ected with fulfilling the FW schedule.