A cross-species comparison of abnormal behavior in three species of singly-housed old world monkeys

Abnormal behavior occurs in a number of captive nonhuman primate species and is often used as an indicator of welfare. However, reported levels of abnormal behavior often vary across species, making general welfare judgments difficult. The purpose of this study was to assess differences in levels of abnormal behavior and associated risk factors across three species of Old World monkeys in order to identify similarities and differences across species. The subjects were 415 (109 females) cynomolgus macaques (Macaca fascicularis), 365 (181 females) rhesus macaques (Macaca mulatta), and 331 (187 females) baboons (Papio hamadryas) that had been singly-housed for 30-120 days. A 5-min observation using one-zero sampling recorded the presence or absence of abnormal behavior for each animal. Macaques exhibited higher levels of abnormal behavior than baboons (29% vs. 14%; χ²(1) = 24.849, p < 0.001), but there was no difference between macaque species (30% vs. 28%; χ²(1) = 0.263, p = 0.608). Risk factors also varied. Overall, males exhibited greater levels of motor stereotypies (b = 0.425, p < 0.05), females greater levels of abnormal appetitive behavior (b = 1.703, p < 0.05), and older animals greater levels of self-directed behavior (b = 0.065, p < 0.05). However, macaques exhibited greater levels of motor stereotypy (b = 2.527, p < 0.001) and self-directed behavior (b = 2.968, p < 0.005) than did baboons. There was also a genus × sex interaction for abnormal appetitive behavior (b = -2.379, p < 0.01) and a genus × age interaction for motor stereotypy (b = -0.167, p < 0.05). These results demonstrate that differences in abnormal behavior exist across closely-related primate species. Therefore, a single species cannot be used generally as a model for abnormal behavior or animal welfare.