A twenty-one-year study of maternal dominance and secondary sex ratio in a colony group of stumptailed macaques (Macaca arctoides)

Trivers and Willard's theory of sex‐ratio adjustment, as applied to cercopithecines, predicts that the ratio of male to female offspring will be greater for dominant than for subordinate mothers. A local‐resourcexyhcompetition hypothesis predicts the reverse. To date, results from several species of macaque are inconsistent and often not statistically significant. In this 21 year study, a colony group of stumptailed macaques is added to the species previously studied. Seventy‐five offspring were born to eight mothers for whom long‐term dominance was established. Chi‐square analyses of data from these 75 offspring failed to yield a significant relationship between sex‐ratio and mother's dominance; consequently, consistent with a growing body of cercopithecine literature, neither of the competing theories was supported. © 1994 Wiley‐Liss, Inc.