Pair housing large adult male cynomolgus monkeys is possible!, the use of telemetry to assess the benefits

Long term pair housing of sexually mature, cynomolgus monkeys in male-male pairs is a common practice based on social needs of the species and research design. This housing paradigm does include risks of aggression, trauma, and impact to studies. Some facilities may forgo attempting to socially house males due to these risks. We sought to leverage the often-easier task of male-female pairing to create longer term, stable pairs as an option to address the social housing needs of sexually mature males. To understand the risk/benefit of this practice, seven vasectomized male monkeys previously implanted with telemetry devices were housed with female counterparts. These animals were selected based on good health, and a history of single housing in a male only study room. The pairing process was gradual with increasing levels of interactions between the male and female occurring over 45 days. At various stages of the pairing process, telemetry data was collected to characterize heart rate, blood pressure, activity, and temperature with data averaged into 2 timebins, 12 am–4 am and 2 pm–6 pm. Initial telemetry was collected when female monkeys were not present in the room and was used for baseline values. A second and third study with different male monkeys were conducted to assess male-male pairing and the influence of cage size on the parameters collected previously. When the females were paired with the males, decreases in blood pressure (−9 mmHg), and increases in body temperature (+0.7 °C) were observed. No significant pairing effects were found for heart rate or physical activity. During the second study, when male animals were re-paired with their male counterparts, blood pressure decreased (−5 mmHg) similar to the male – female pairing study. In the third study, no significant cage size effect was noted on physiologic parameters. These reductions in blood pressure indicate a lower stress in paired animals unrelated to sex or cage size. This further supports the benefits of pair housing monkeys in a research environment. In conclusion, pairing vasectomized male monkeys with female monkeys is a viable option for long term telemetry colonies using single housed male animals.