Using preference-assessment tests with humans in conjunction with behavioral modification sessions has been a regular component of almost all operant conditioning programs with mentally challenged humans. This has been very effective in improving the efficiency of behavioral training in these settings and could be similarly effective in zoological and research environments. This study investigated the preferences of 9 captive orangutans for different food items. The study used a pairwise presentation to record each nonhuman animal's preferences for 5 different foods on 6 different occasions over the course of 6 months. Results of a Friedman's 2-way ANOVA indicated that the orangutans showed a clear overall preference for apple. However, there was significant variability among different orangutans in preference ranking for the 5 foods, as shown by a Kendall's tau. In addition, there was variability in preference rankings across time for each orangutan. Because the orangutans' preferences change over time and vary according to individual, regular assessments should identify items to be used as rewards in behavioral husbandry training or as part of feeding enrichment strategies.

Scientific evaluation of management strategies for captive species is part of the establishment of best practices for animal welfare. Here we report the effects of sex, rearing, and a sex-by-rearing interaction on adult, captive chimpanzees' (Pan troglodytes) behavior, health, well-being, personality, and orientation towards humans based on multiple methods (observation, animal records, and surveys). Chimpanzees raised in three conditions, mother-reared (MR), standard nursery (ST) and an experimental nursery (RC), were assessed approximately 20 years after their differential rearing experiences concluded. Sex had a significant effect on behavior towards conspecifics (aggression [M > F]; affiliation [F > M]), on abnormal behavior (rocking [M > F]), and on likelihood of incurring at least one injury (between ages 6 and 10 [M > F]). Rearing condition had a significant impact on behavior towards humans (negative solicitation [RC = ST > MR = ST]; neutral behavior [RC > ST > MR], yawning (RC = ST > MR = ST), subjective well-being (MR = ST > RC = ST), and on GI illness frequency (RC > ST = MR). Sex interacted with rearing on aggression towards humans (for males, RC > MR = ST), frequency of upper respiratory infection (URI: for males RC > MR = ST)) and likelihood of at least one URI between the ages of 11 and 15 (RC males > ST males). Our findings support the conclusion that there are long-term effects of both early rearing and sex on captive adult chimpanzee welfare.

A survey was sent to zoos, research facilities, and sanctuaries which housed chimpanzees. Data collected included information about 1122 chimpanzees’ age, sex, social group-size, rearing history, and enclosure. Respondents were also asked to indicate if certain behaviors had been observed in each chimpanzee over the prior two years. Species- typical behaviors (STBs) were queried, including copulation, tool-use, nest-building, and social grooming. Tool-use was reported present for 94.3% of the sample (n = 982), active social grooming for 85.7% (n = 1121), copulation for 68.3% (n = 863) and nest-building for 58.9% (n = 982). Of the subjects for whom we had data regarding all four STBs (n = 860), 45.6% were reported to engage in all four. Logistic regression analyses using forward Wald criteria were conducted to determine the best model for each STB based on the predictors of age, sex, rearing history, group-size, facility-type, and a sex-by-rearing interaction. The best model for copulation (χ²(6) = 124.62, p < 0.001) included rearing, group-size, facility-type, and the sex-by-rearing interaction. Chimpanzees were more likely to copulate if they were mother-reared, in larger groups, living in research facilities, and, if not mother-reared (NOTMR), more likely to copulate if they were female. The best model for tool-use retained the predictors of age category, facility-type, and sex-by-rearing (χ²(5) = 55.78, p < 0.001). Chimpanzees were more likely to use tools if they were adult, living in research facilities, and if NOTMR, were female. The best model for nest-building included facility-type and rearing (χ²(3) = 205.71, p < 0.001). Chimpanzees were more likely to build nests if they were MR and if they were living in zoos or in sanctuaries. The best model for active social grooming retained the predictors of age, sex, rearing, and type of facility (χ²(6) = 102.15, p < 0.001). Chimpanzees were more likely to engage in active social grooming if they were immature, female, mother-reared, and living in zoos. This research provides a basic behavioral profile for many chimpanzees living under human care in the United States and allows us to determine potential methods for improving the welfare of these and future chimpanzees in this population.