Reinhardt, V., Cowley, D., Eisele, S. 1991. Serum cortisol concentrations of single-housed and isosexually pair-housed adult rhesus macaques. Journal of Experimental Animal Science 34(2), 73-76.

Possible social distress was evaluated in 20 adult rhesus macaques housed in compatible isosexual pairs (5 female pairs, 5 male pairs) for the purpose of social environmental enrichment. Serum cortisol concentrations of paired animals were compared with serum cortisol concentrations of individually housed adult rhesus macaques of both sexes (5 females, 5 males). In both sexes, cortisol concentrations of paired animals showed no significant difference with those of single animals. Both in male and in female pairs, dominant partners had cortisol concentrations that were equivalent to those of their subordinate counterparts. It was concluded that neither female nor male adult rhesus macaques experience more distress when sharing a cage with a compatible partner of the same sex than when living alone.