Bayne, K., Dexter, S. L., Mainzer H et al. 1992. The use of artificial turf as a foraging substrate for individually housed rhesus monkeys (Macaca mulatta). Animal Welfare 1, 39-53.

In this study artificial turf was used as the substrate for a particulate food given to the subjects as an environmental enrichment technique. When their cages were not enriched, eight single-caged subjects exhibited abnormal behaviors approximately 37% of the time. An increasing trend in time spent foraging with a concomitant decline in aberrant behaviour over a time period of six months was particularly noteworthy [in the single-housed subjects]. Subjects spent on average 15.7 minutes per 30 minute observation sessions foraging from the device. Stereotypic abnormal behaviours and excessive repetitive locomotion are perhaps the two most frequently observed behavioural pathologies in laboratory primates.