Studies have shown that social housing of compatible pairs leads to positive social interactions and the expression of species-appropriate social behavior not possible in single housing. The Guide for the Care and Use of Laboratory Animals recommends that social animals be housed with members of the same species whenever possible. Rhesus macaques are social animals by nature and for this reason their social needs must be addressed under federal regulation. The most commonly used nonhuman primates in biomedical research are rhesus macaques.

The results of this study may be of practical use for designing and monitoring social introductions and suggest that managers should not dismiss the feasibility of successful pairing of adult male rhesus macaques. The fact that reductions in abnormal behavior did not persist over the long term may have been confounded by increasing duration of time spent caged. Fecal cortisol levels were lower in settled pairs than in single housing. Heart rates during introduction fell significantly in the settled pair phase, and also varied predictably with time of day. Levels of abnormal behaviors, psychological indices of distress, locomotion, inactivity, and affiliation showed improvements within several weeks after introduction these changes were still present 5–9 months later for the latter two categories. Agonism was minimal throughout the introduction process and over the subsequent months only one wound was incurred over the course of the study. All introductions were successful and subjects showed no physiological or behavioral signs of stress, such as increased heart rate, abnormal behavior, or psychological indices of distress (depressive/anxiety-related behavior).

Fecal cortisol was also measured for the baseline, post-introduction, and settled pair phases. One hundred and seventy-six hours of behavioral data and 672 hr of heart rate data were analyzed. Socially experienced subjects, all implanted with biotelemetry devices, were studied in five successive phases: baseline (singly housed), 1 day each of protected contact and full contact introduction, post-introduction (1–3 weeks after introduction), and settled pairs (≥20 weeks after introduction).

Behavioral and physiological data were collected on eight adult male rhesus macaques before, during, and after the process of introduction, in order to measure the initial stress of introduction as well as long-term changes in well-being.

Pair housing of laboratory macaques is widely considered to lead to positive changes in well-being, yet the process of introduction is viewed as potentially stressful and risk-prone.

Her Reluctant Groom by Rose Gordon