Enrichment object preferences in laboratory rhesus monkeys (Macaca mulatta) (2013)

Carey, M. C., West, A. M., Diaz, B. et al.

Abstract

To promote the psychological well-being of captive non-human primates, facilities develop and implement an environmental enhancement plan (Animal Welfare Act, Section 3.81). Enrichment options described in the plan should be selected to demonstrably promote species-typical behaviors. Too often, enrichment choices are based only on anecdotal reports or just what people think might be interesting. That is a start, but a better course is to carefully evaluate use and effectiveness of enrichment objects to enable evidence-based enrichment. To this end, non-disposable feeders were constructed by drilling holes into Manzanita wood (MW), filling them with peanut butter and foraging mix. The disposable feeders were constructed by coating pine-cones (PC) in peanut butter and foraging mix. The colony of adult male rhesus macaques (n=20) were simultaneously provided both MW and PC foraging devices three times a week for three weeks. Observations were recorded for a total of 45 minutes per individual over five weeks (including pre and post-test observations) and frequency of foraging behaviors were scored to determine preference. The null-hypothesis of no difference between mean foraging with disposable and non-disposable enrichment was rejected as the PC devices were used more than three times the MW devices with minimal decline in use across three weeks (PC =8.11 +/- 0.058 > MW =2.74 +/- 0.057; p<0.0001). Pine-cone feeders appear to be a preferred device to encourage natural foraging behavior in captive rhesus.