Use of animal-operated folding perches by rhesus macaques (Macaca mulatta)

Providing captive or laboratory animals with the best possible living conditions has led to many ideas about how caging environments can be enhanced and the animals' lives can be enriched. This study focused primarily on 2 issues: more efficient use of existing caging and providing animals with a measure of control over their environments. We designed a new springloaded folding perching apparatus that, when modified for size, could be added to almost any caging system. Experiment 1 measured usage by animals in standard laboratory caging for rhesus macaque monkeys (Macaca mulatta). Experiment 2 measured usage by this same species in social groups in a 5-acre outdoor-indoor field setting, where several other forms of enrichment were available to the animals. Results indicated that the folding perches were used in both environments. Animals quickly learned to fold down the devices to use as a place to perch, even in the presence of permanent fixed perches. The folding perches did not significantly affect existing behavioral repertoires, but they altered how the animal used the cage. Increased animal presence near folding perches during experiment 2 suggests that these devices actually were preferred. The preference results can only partially be explained by novelty. The folding perches afforded animals a measure of control over their immediate environment without interfering in research or animal care efforts. Including at least 1 folding perch per cage satisfies both the letter and the spirit of regulations on environmental enhancement for captive primates.