Variables influencing the origins of diverse abnormal behaviors in a largesample of captive chimpanzees (Pan troglodytes)

The developmental origin of abnormal behaviors is generally associated with early rearing environments that lack sufficient physical and sensory stimu lation. However, other factors should also be considered. A large sample of captive chimpanzees (128 males and 140 females) was surveyed for the prese nce or absence of 18 abnormal behaviors. Origin variables included the subj ect's source (zoo, pet, performer, or laboratory), rearing (mother- or hand -reared), and sex. Animals were assessed while held at the Primate Foundati on of Arizona, University of Texas M. D. Anderson Cancer Center, or White S ands Research Center. There was a confound among origin variables; more han d-reared animals than expected were from laboratories. Logistic regression tested the relationship of rearing and source, with sex as a secondary pred ictor variable, to each of the abnormal behaviors. There was no clear assoc iation between any abnormal behavior and source. However, for coprophagy, r elative to animals from the laboratory, zoo animals tended to show a higher prevalence, while performers tended to show a lower prevalence (when reari ng and sex were controlled). Rocking and self-sucking were significantly mo re likely in hand-reared animals. Coprophagy and depilation of self were si gnificantly more likely in mother-reared animals. When rearing and source w ere statistically controlled, the only significant sex difference was a hig her prevalence of coprophagy in females and a higher prevalence of rocking in males. In a second, smaller sample of 25 males and 33 females from South west Foundation for Biomedical Research, no significant sex association was found for coprophagy, urophagy, rocking, or self-depilation. In this secon d sample, coprophagy was also significantly more likely in mother-reared th an hand-reaped subjects. The association of some abnormal behaviors with mo ther-rearing suggests that some form of social learning may be involved in the origin of some of these behavior patterns. This indicates that some abn ormal behaviors may not be always be indicative of reduced psychological we ll-being in captive chimpanzees. Am. J. Primatol. 48:15-29, 1999. (C) 1999 Wiley-Liss, Inc.