Pair housing of macaques in research facilities: a science-based review of benefits and risks.

Despite the enactment in the early 1990s of regulations requiring social housing of nonhuman primates (NHP), single housing is still prevalent in American research facilities. The publication of the 2011 edition of The Guide for the Care and Use of Laboratory Animals has increased emphasis on the implementation of social housing as the default housing method for NHP. Overestimation of the risks inherent in social housing coupled with underestimation of both the benefits of social housing and the risks inherent in long-term single housing has prevented large-scale transitions to social housing. Available caging and housing space often requires research facilities to use isosexual pairs to accomplish social housing. Pair housing presents unique challenges but can be used safely with a thorough understanding of macaque ethology. Here we review literature on the risks and benefits of pair housing macaques in research facilities and provide a concise best-practice approach to pair housing.