Characterizing abnormal behavior in a large population of zoo-housed chimpanzees: prevalence and potential influencing factors

Abstract

Abnormal behaviors in captive animals are generally defined as behaviors that are atypical for the species and are often considered to be indicators of poor welfare. Although some abnormal behaviors have been empirically linked to conditions related to elevated stress and compromised welfare in primates, others have little or no evidence on which to base such a relationship. The objective of this study was to investigate a recent claim that abnormal behavior is endemic in the captive population by surveying a broad sample of chimpanzees (Pan troglodytes), while also considering factors associated with the origins of these behaviors. We surveyed animal care staff from 26 accredited zoos to assess the prevalence of abnormal behavior in a large sample of chimpanzees in the United States for which we had information on origin and rearing history. Our results demonstrated that 64% of this sample was reported to engage in some form of abnormal behavior in the past two years and 48% of chimpanzees engaged in abnormal behavior other than coprophagy. Logistic regression models were used to analyze the historical variables that best predicted the occurrence of all abnormal behavior, any abnormal behavior that was not coprophagy, and coprophagy. Rearing had opposing effects on the occurrence of coprophagy and the other abnormal behaviors such that mother-reared individuals were more likely to perform coprophagy, whereas non-mother-reared individuals were more likely to perform other abnormal behaviors. These results support the assertion that coprophagy may be classified separately when assessing abnormal behavior and the welfare of captive chimpanzees. This robust evaluation of the prevalence of abnormal behavior in our sample from the U.S. zoo population also demonstrates the importance of considering the contribution of historical variables to present behavior, in order to better understand the causes of these behaviors and any potential relationship to psychological wellbeing.

A Model Quantitative Assessment Tool for Nonhuman Primate Environmental Enrichment Plans

“…Research on the effects of EE has often focused on the reduction of what are termed "abnormal" behaviors, including stereotypies (i.e., rocking, body flips), self-directed behavior (i.e., digit-sucking, hair pulling ), self-injurious behavior (i.e., self-biting, selfwounding) that occur in a some primates in a broad range of captive settings (for review c.f., Jacobson, Ross, & Bloomsmith, 2016;Lutz, 2014;Mason, 1991;Novak, Hamel, Ryan, Menard, & Meyer, 2017). We view this type of research as approaching evaluation of EE from a "clinical treatment" model, one that is focused on reducing behavioral symptoms that can be associated with compromised psychological and physical welfare.…”

“…In reports published after 2000, estimates of prevalence of abnormal behavior are wide-ranging. For instance, a sampling of reports on the percentage of animals exhibiting abnormal behavior include: 13% of prosimian primates in a US zoo (Tarou, Bloomsmith, & Maple, 2005); 48-64% of chimpanzees in 26 accredited US zoos (Jacobson et al, 2016); 89% of singly-housed rhesus macaques in a former US research facility (Lutz, Well, & Novak, 2003) ; and 90% of singly-housed cynomolgus macaques in a Chinese research facility (Camus, Blois-Heulin, Li, Hausberger, & Bezard, 2013).…”

“…A study of 231 rhesus monkeys reported that over 50% exhibited what the authors termed "self-abuse," but there was insufficient detail to yield prevalence estimates for SSIB (Rommeck, Anderson, Heagerty, Cameron, & McCowan, 2009). In a study of chimpanzees in 26 accredited US zoos, roughly 2% were reported to exhibit self-injurious behavior (Jacobson et al, 2016). Similarly, roughly 2% of 540 primates housed in 35 zoos and including prosimians, New and Old World Monkeys, and apes in British and Irish zoos were reported to engage in self-biting (Hosey & Skyner, 2007).…”

“…For instance, some animals imported for zoos, breeding, or research may have lived in facilities with large outdoor housing and then been transferred to smaller indoor housing. In the case of zoos and sanctuaries, some animals may have lived in private homes and then been transferred to social groups and facility housing (Jacobson et al, 2016) .…”

“…Hook and her colleagues (2002) have provided evidence from a study of 8 chimpanzee groups and 21 rhesus macaque social groups that: "Variance in the expression of abnormal behaviors across groups of chimpanzees and rhesus monkeys suggests that social learning processes are involved in the propagation of these behaviors and thus, the study of abnormal behaviors may be a suitable method for further examining the question of culture in non-human primates." In the same vein, others have concluded that a high prevalence of a specific NSSIB behavior indicates that it is social transmitted and should not be considered abnormal (e.g., coprophagy in zoo chimpanzees; Jacobson et al, 2016).…”