Abstract Some wildlife biologists and managers are concerned that ungulate population productivity may decline when hunting causes a bias in the male age structure favoring young males. Young males are assumed to be incapable of successfully courting females, to prolong the mating season, to create confusion during mating because of unstable social hierarchies, or to cause some combination of these. Here, results are presented of a natural experiment involving two bighorn sheep ( Ovis canadensis candensis) populations: one unhunted and the other where most of the mature males were removed during the hunting season. One month later, the remaining young males courted and successfully copulated with adult estrous females. Comparing courtship behavior of these young males with that of males more than three times their age in the unhunted population with a “typical” male age structure, showed no significant qualitative or quantitative differences. However, young males in the unhunted population not only failed to copulate with estrous females but also performed mainly immature patterns in male-male interactions, even when they were the largest males in the interaction. Social maturation in mountain sheep is not simply a function of chronological age but is related to a population's social structure and composition.