Effects of sex and early rearing condition on adult behavior, health, and well-being in captive chimpanzees (Pan troglodytes)

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.