Heagerty, A. L., Coleman, K. 2018. Amount and reciprocity of affiliative behaviors can predict pairing success in captive rhesus macaques (Macaca mulatta). American Journal of Primatology 80(S1), 47 (40th Meeting of the American Society of Primatologists Scientific Program, Abstract #148).

Socialization is one of the most important forms of enrichment for rhesus macaques. However, pair introductions can result in aggression and injury if partners are incompatible, even days after the initial introduction. Identifying predictors of long‐term compatibility early on can reduce potential stress and injury to animals. We analyzed data from ten‐minute focal observations during the first Day of 641 female‐female and 472 male‐male rhesus macaque introductions to identify predictors of pairing success (i.e., co‐housed in full contact without inappropriate aggression or fear for over 14 days). 73% of female‐female pairs and 74% of male‐male pairs were successful. Behaviors coded included grooming, rump presents, mounting, and tandem threats (cooperative threat to another individual) and were recorded as present/absent for each animal during 30 20‐second intervals. We found that both the total amount of affiliation and the amount of affiliation reciprocated between partners predicted success. Successful female pairs showed more tandem threats (t = 9.3, p < 0.001), grooming (t = 3.5, p < 0.001), and reciprocal grooming (t = 2.3, p = 0.02) than unsuccessful pairs. Successful male pairs showed more tandem threats (t = 5.7, p < 0.001), grooming (t = 4.8, p < 0.001), mounting (t = 6.8, p < 0.001), reciprocal mounting (t = 4.7, p < 0.001), and reciprocal rump presents (t = 2.6, p = 0.01) than unsuccessful pairs. Although the specific behaviors differed for males and females, these results show that the amount of affiliation and the reciprocation of particular behaviors early in the introduction process can predict pair compatibility.