Hanniba, D., Beisner, B., Nathman, A. et al. 2018. Removals based on low within-matriline relatedness can reduce severe aggression in captive rhesus macaques. American Journal of Primatology 80(S1), 48 (40th Meeting of the American Society of Primatologists Scientific Program, Abstract #151).
Previous observational research of captive rhesus macaques suggests that higher coefficients of relatedness within matrilines are associated with lower rates of severe within‐matriline aggression and more cohesive grooming communities. We tested whether experimental removals targeted to increase the relatedness coefficient of remaining matriline members leads to fewer grooming communities and a lower ratio of severe aggression within matrilines. The study sample was comprised of 100 adult females within 13 matrilines in 1 mixed‐age‐sex group. The Girvan‐Newman method was used to detect communities and modularity (score Q) within matrilines. We used generalized linear regression models to determine the best model predicting the ratio of severe within‐matriline aggression. Seven matrilines received experienced removals and results show fewer grooming communities in those matrilines (Beta = −1.33, p = 0.04), but not a reduction in modularity (Beta = 0.04, p = 0.99). The coefficient of relatedness was negatively correlated with number of grooming communities (rho = −0.52, p < 0.001) and modularity (rho = −0.58, p < 0.001), so these had to be tested separately rather than in one model. The number of grooming communities (Beta = 0.11, p = 0.03) within matrilines was a better predictor of the ratio of severe aggression than coefficient of relatedness (Beta = 0.72; p = 0.36) or modularity (Beta = −0.14, p = 0.82). These results show that the coefficient of relatedness can be a useful management tool to selectively remove individuals from captive rhesus macaque social groups as long as it results in fewer grooming communities within targeted matrilines.