Influence of food enrichment on cage side preference

A preference test paradigm was used to assess the value of two enrichment techniques for rhesus macaques (Macaca mulatta): 1) a Kong toy stuffed with food treats and 2) a fleece board covered with particulate food. The duration of time spent in the enriched cage side was compared with that spent in the unenriched cage side. Additionally, the number of cage side changes made during an observation interval and the duration and frequency of occurrence of select behaviors were recorded. Half the subjects altered their cage side preference during the experimental condition, and a fifth animal reversed side preference in the postexperimental phase. Subjects spent a mean time of 14% of a session engaged with the foraging devices. The occurrence of several behaviors, including self-directed and locomotor activities, varied significantly with the experimental condition. These results were compared with data from a previous preference study of nonnutritive enrichments, and a hypothesis regarding the relative value of different types of enrichment was developed.