Rigid plastic balls as enrichment devices for captive chimpanzees.

The use of rigid, plastic balls as enrichment devices for 16 captive chimpanzees was studied at The University of Texas M.D. Anderson Cancer Center chimpanzee colony. After the subjects were presented with balls, 10 hours of data were collected for each subject using a scan-sampling technique. The mean percentage of ball-use time for all subjects during the study was 7.1%. There was no sex difference in ball use. Age and housing effects were obtained, with younger animals and those housed in more barren environments exhibiting higher levels of ball use. It is concluded that the balls were worthwhile additions to the chimpanzee environments with use stabilizing at a mean of 2.5% of the subjects' time.