lives in troops, or groups, of up to 40 monkeys (mean 16, range 4–40) and has a male/female adult sex ratio of 0.71 on average (range 0.54–0.88). With rare exceptions, females spend their entire lives with their female kin. Males migrate to new social groups multiple times during the course of their lifetimes, migrating for the first time between 20 months and 11 years of age. The median age of migration in the Santa Rosa population is 4.5 years. Males sometimes migrate alone, but more often they migrate in the company of other males who are often their kin. One of the unusual features of the kinship structure of the white-headed capuchin, relative to other primate species, is the high degree of relatedness within groups that results from the long tenures of alpha males who sire most of the offspring. Alpha males have been known to keep their positions as long as 17 years in this species and this puts them in the unusual position of being available to sire the offspring of their daughters and granddaughters, who produce their first offspring at about 6–7 years of age. Typically, however, alpha males do not breed with their own daughters, even though they do sire virtually all offspring produced by females unrelated to them. Those subordinate males who are allies of the alpha male in group defense are the males who sire the offspring of the alpha male's daughters. The high degree to which alpha males monopolize matings results in an unusually large number of paternal half-siblings and full siblings in this species relative to other primate species.