Depression-like trait in rescued rhesus macaques (Macaca mulatta) in Central Zoo, Kathmandu, Nepal: Influence of rearing history and social status

Abstract

Zoos serve for education, research, conservation, recreation and rehabilitation for wildlife. Multiple factors including social integration, agonistic interactions and rearing conditions influence the development of depression-like traits among zoo-housed animals. This study examined influence of social status and rearing history on social withdrawal behavior (SWB), a trait resembling depression, among rhesus macaques at the Central Zoo, Jawalakhel, Nepal. The subjects were; two captive-reared males and four females (2 captive-reared; 2 rescued). Observations were conducted using 30-minute focal sampling sessions (n = 443) for four months to record the frequency and duration of key behaviors, such as grooming, agonistic, and SWB. Social network analysis was used to quantify social integration through eigenvector centrality (EC). Results revealed strong heterogeneity in social positions, with withdrawal behavior concentrated in socially peripheral individuals. A significant negative correlation was found between EC and SWB; while log-transformed linear models revealed that individuals with rescued rearing history and EC were the strongest predictors of SWB. Agonistic interaction received was associated with both low social status and increased withdrawal, suggesting an indirect pathway linking social status and behavioral outcomes. These findings indicate social status and rearing history significantly influence SWB in macaques when introduced into established social hierarchies. The study recommends that zoos implement tailored interventions for rescued macaques to mitigate social stress and support their psychological well-being.