Most studies of partner choice and preferences in nonhuman primates have been concerned with male social rank. Females select high-ranking males, and high-ranking females can more readily gain access to males. Although researchers have mentioned males’ choices and their preferences for females, papers that focus on male preferences have been few. Past studies suggested that male primates prefer older females. We analyzed data collected by the every-other-day mating system in which a male alternately lived with each of two females. This allowed us to compare the biological and/or physical characteristics of pregnant females with those of nonpregnant females and to minimize social factors. Multiparous and/or older females were more frequently pregnant. In the nulliparous group, females that became pregnant for the first time tended to be younger than the other nonpregnant females paired in the mating set. While males generally prefer parous females, males prefer to mate with younger females among females that have never been pregnant. A female that gets pregnant at a young age could become pregnant again later in life. Such a mating preference would guarantee higher reproductive success for females in the wild as well
