Female fertile phase synchrony, and male mating and reproductive skew, in the crested macaque

High social status is the primary determinant of reproductive success
among group-living male mammals. Primates living in multimale–multifemale
groups show the greatest variation in the strength of this link, with
marked variation in reproductive skew by male dominance among species,
dependent on the degree of female fertile phase synchrony, and the number
of competing males. Here, we present data on two groups of wild crested
macaques (Macaca nigra), living in the Tangkoko Reserve, Sulawesi,
Indonesia. We investigated male monopolization of fertile females in 31
cycles of 19 females, and genetic paternity of 14 offspring conceived
during the study period. We show that female fertile phase synchrony was
low, that females had few mating partners in their fertile phase, and that
dominant males monopolized a high proportion of consortships and matings,
resulting in marked and steep mating and reproductive skew. We conclude
that female cycle asynchrony provides the opportunity for strong direct
male–male competition in crested macaques, resulting in monopolization of
females by dominant males, consistent with their marked sexual dimorphism.
Our study provides a test of the underlying factors that determine the
relative occurrence and strength of different mechanisms of sexual
selection, and the phenotypes that evolve as a result.