Social Housing of Previously Single-Caged Adult Male Cynomolgus Macaques (Macaca fascicularis).

Cynomolgus macaques (Macaca fascicularis; Mf) serve an essential role in the advancement of biomedical research. Aged macaques, in particular, are highly valued as animal models for the study of geriatric diseases. While social housing has become the default for nonhuman primates (NHPs), socially housing sexually mature males poses a unique challenge. Moreover, socially housing aged males that have been previously kept in single housing may pose even greater challenge and risk due to a higher likelihood of aggression. Temperament assessment plays an integral part in determining the success of social housing arrangements of NHPs. In this paper, we report our work at the Primate Research Center of IPB University in integrating behavior observation and veterinary management to socially house adult, male Mf. We describe our experience in successfully housing young-adult, male Mf (n = 8-10, aged 6 years) for over 2.5 years, and the multiple efforts to socially house a small group of previously singly housed aged, male Mf (n = 6, aged >15 years). The temperament of each Mf was considered in the planning and implementation of social housing attempts. While a simplified behavioral observation was performed for the young adults, a more rigorous PAIR-T assessment was performed on the aged Mf. A group formation was initially attempted, aiming to achieve a small group of six aged, male Mf. While this group at first showed promising outcomes, significant incidents of aggression required regrouping as pairs or triads wherein the subject combinations were determined based on temperament and dominance. A total of three attempts were made to house these aged Mf in a small group throughout the course of 17 months, and the results showed that at our facility, aged, male Mf are best housed as triads or pairs, with selections based on their temperament and dominance compatibility. We concluded that behavioral assessments and veterinary management are pivotal in supporting the social housing efforts of adult, male Mf in order to optimize their well-being.