Abney, D. M., Toscano, J. E., Poor, L. L. et al. 2014. Successful social housing of adult male cynomolgus macaques with similar bodyweights. American Journal of Primatology 76(S1), 86. (37th Meeting of the American Society of Primatologists Scientific Program, Abstract #151)

At Charles River Laboratories, we are committed to ensuring all animals have the highest level of care and welfare. To this end, our social housing program includes placing all nonhuman primates in pairs or groups. We have a rate of almost 100% success social housing juvenile, sub-adult, and adult female cynomolgus macaques (Macaca fascicularis). Social housing of sexually mature males, however, can be a challenge. Some publications suggest a large weight differential among males increases the likelihood of social pairing success, however many scientific projects require a narrowly defined weight range between subjects. Over a one year period, data were reviewed for 82 attempted pairs assigned to 14 different studies to assess the success associated with social housing males of similar body weights. The mean difference in body weight was 1.0 kg ± 0.08 kg. Sexually mature males were defined as 5 kg or greater and pairing success was defined as full contact social housing maintained for a minimum of two weeks. Data were analyzed to assess if there was statistical significance in pairing success by a weight differential within the pair of ± 1 kg and no significance was found (χ2 = 0.36, df= 1, P=0.5). This data suggests that body weight does not seem to play a significant role in determining social success for adult male cynomolgus macaques and should not be seen as a deterrent to social housing attempts.