Foraging behavior of pigeons (Columba livia) in situations of diminishing returns using a reinforcement schedule that controls the energy expenditure of responses

Abstract

Animal foraging behavior has received much attention in the fields of biology and psychology. Many studies have examined this behavior using optimal foraging theory as the theoretical framework, which explains that animals behave in a way that optimizes net energy intake (calculated by dividing the difference in energy obtained from prey and energy expended for foraging by the total time engaging in these behaviors). This study simulated the foraging situation assumed in Charnov’s (Theoretical Population Biology, 9, 129–136, 1976) marginal value theorem—namely, where food is located in patches separated by areas without food. To quantitatively analyze the behavior of homing pigeons (Columba livia) in terms of the marginal value theorem, we conducted a series of experiments using a reinforcement schedule that controls the energy of responses (Kono, Learning & Behavior, 41,425–432, 2013). Experiment 1 revealed that pigeons’ behavior was qualitatively consistent with the prediction of the marginal value theorem, but the energy schedule weakly controlled the energy expenditure of behavior. In Experiment 2, the procedure was modified to more strictly control energy expenditure. The results showed that the pigeons’ behavior was relatively close to that of the predicted value of the marginal value theorem. Overall, then, pigeons behaved optimally in foraging as predicted by the marginal value theorem. However, individual differences were observed, particularly when schedule requirements were high. Future studies should examine the underlying cause of this result.