Food-pellet size modifies the hoarding behavior of foraging rats

Abstract

Rats were allowed to forage for different-sized (20- to 500-mg) food pellets from a cage attached to a straight alley or from a cage placed in the center of an 8-arm radial maze. In both tasks, food-pellet size influenced motor responses. Small food pellets were swallowed at the food source. Medium-sized food pellets were grasped by mouth, and, after the rat stepped away from (dodged) the food source, they were eaten as the rat adopted a sitting posture. Large food pellets were hoarded to the adjacent enclosure. The food-related motor patterns prevailed despite changes in the distance to the food source, despite changes in the rats’ deprivation level, and after visual occlusion. If hoarding was frustrated by blocking the home cage entrance, dodging angle and distance were still proportional to food-pellet size. Food size did not, however, influence selection of arms on an 8-arm maze with arms consistently associated with food pellets of given size. The novel contribution of this study is the demonstration that stimulus features associated with food size influence motor behavior, including the complex motor sequence involved in hoarding food. This paradigm not only provides new information about factors that influence hoarding in the rat, but also should prove useful for the study of food-related motor behavior of the rat and its neural control.