Effects of pair housing on behavior, cortisol, and clinical outcomes during quarantine‐like procedures for rhesus macaques (Macaca mulatta)

Background Compatible pair housing of macaques in research settings increases species‐typical behaviors and facilitates beneficial social buffering. It is not yet established whether these benefits are maintained after intrafacility transfer and domestic quarantine, which are two stressors that can lead to behavioral and clinical abnormalities. Methods We evaluated 40 adolescent male rhesus macaques who were single‐ or pair‐housed immediately following an intrafacility transfer. We measured behavior, fecal cortisol, body weight, and diarrhea occurrence. Body weight and diarrhea occurrence were also retrospectively analyzed in an additional 120 adolescent rhesus who underwent a similar transfer. Results and Conclusions Pair‐housed macaques exhibited less of some undesirable behaviors (e.g., self‐clasping) and experienced less diarrhea than single‐housed subjects; however, no significant differences in cortisol levels or alopecia measures were found. The demonstrated beneficial effects of pair housing for rhesus macaques following intrafacility transfer and adjustment suggest pairing upon arrival at a new facility will bolster animal welfare.