Rats (Rattus norvegicus) and pigeons (Columbia livia) are sensitive to the distance to food, but only rats request more food when distance increases

Three experiments investigated foraging by rats and pigeons. In Experiment 1, each response on a manipulandum delivered food to a cup, with the distance between the manipulandum and the cup varying across conditions. The number of responses made before traveling to collect and eat the food increased with distance for rats, but not for pigeons. In Experiment 2, two manipulanda were placed at different distances from a fixed food source; both pigeons and rats preferentially used the manipulandum closest to the food source. Experiment 3 was a systematic replication of Experiment 1 with pigeons. In different conditions, each peck on the left key increased the upcoming hopper duration by 0.5, 1.5 or 2.5 s. Completing a ratio requirement on the right key of 1, 4, 8, 16 or 32 pecks, depending on the condition, then produced the food hopper for a duration that depended on the number of prior left pecks. As the ratio requirement increased on the right key, pigeons responded more on the left key and earned more food. Overall, the results replicate previous research, underlining similarities and differences between these species. The results are discussed in terms of optimal foraging, reinforcer sensitivity and delay discounting.

► Rats adjust the amount they will receive before travel to a distant patch as a function of the distance; pigeons do not.
► Both rats and pigeons prefer to work close to the source of food, and that preference is a power function of the relative distance.
► Pigeons will differentially increment the size of a deferred reinforcer as a function of the number of key pecks required to obtain it.