Leland, S. P., West, A. M., Shaver, C. K. et al. 2008. Longitudinal comparison of rates of species-typical behavior of chimpanzees (Pan troglodytes) in an enriched laboratory environment. American Journal of Primatology 70(S1), 51. (31st Meeting of the American Society of Primatologists Scientific Program, Abstract #92)

Behavioral observations were conducted as an ongoing program of monitoring psychological well-being of chimpanzees involved in IACUC-approved preventive medicine studies. The chimpanzees were housed in a facility that provided a variety of enrichment objects, climbing structures, and glass-walled enclosures that permitted visual and auditory access to conspecifics. Seventeen chimpanzees ranging in age from 19 to 83 months were each observed one hour per day for 15 days, using five-minute point-sampling. Fifteen of the seventeen chimpanzees were singly-housed in accordance with research protocols, while the two youngest were paired together. An average of 92.6% of observation time included no abnormal patterns of behavior. Additionally, special attention was given to observations of seven individuals for whom this was the third set of intensive observations (Phase 3). These three phases of observations were conducted over a two year period (approximately one year apart). During Phase 1, five of these seven individuals were housed in direct social contact situations (one triad, and one dyad), while two were individually housed. All seven subjects were housed individually during and between Phase 2 and Phase 3. An average of >90% of observation sessions included no abnormal behavior during any of the three phases. No species-typical pattern of behavior significantly changed between or across the 3 phases in pair-wise repeated-measures tests [Wilcoxon Signed Rank Test; α=0.05]. These enriched conditions did not increase atypical behaviors.