Female Mate Choice Based On Male Age And Phenotype In Golden Snub-nosed Monkeys(Rhinopithecus Roxellana)

In many species,age is a key factor affecting sexual selection,as many aspects of individual physical and social status are strongly associated with age.Especially in the monogamy system,the high rate of physical injury caused by frequent aggressive behavior between males accelerates rapidly with age,leading to a high rate of physical injury and mortality.Although studies of mate choice in primates often consider particular traits related to age,few consider the collective effects of male age per se.The social system of the golden snub-nosed monkey(Rhinopithecus roxellana)is a multilevel society with one-male unit(OMU)and all-male unit(AMU)as the basic unit.Long-term behavioral studies have found that individuals transfer,extra-unit copulation,and male takeover occurred frequently in the troop.However,the social mating system does not match with the actual genetic mating relationship,females maybe have different strategies when choosing the social males or extra-unit males.Therefore,it is important to explore age-based mate choice preferences of golden snub-nosed monkeys from behaviour for understanding of their strategies of mate choice and the formation of the mating system.We examined the relationship between females mate choice and males age during a3-year study of a troop in the Dapingyu region of the Guanyinshan National Nature Reserve(GNNR)in the Qinling Mountains,China.We tested females preference for male age when choosing mates in this group and the correlation between male age and some phenotypes was analyzed.The influence of some phenotypes on the female mate choice of this species was also explored.We found that:1.the number of females of the resident male in an OMU tended to increase up at the age of 7 or 8,and to decline after about the age of 12,such that prime age resident males had more females than other resident males.In other words,prime age males were more likely to be resident males of OMUs than males of other ages.2.extra-unit copulation data indicated that females chose 10-15 year old males more than others.Nevertheless,evidence from female transfers showed that females tended to move from older,prime age resident males to younger resident males(7-9 years).Although resident male rank was positively and linearly correlated with male age,such that young males were lower ranking than prime aged males.We speculate that females may perceive early signs of aging in males and trade off the benefits and costs of high rank vs.male senescence.Thus,females appear to use different strategies when choosing social mates and extra-unit mates.3.we found that the age of males is significantly correlated with the granulomas and sharpness of canine teeth through examining the phenotypic characteristics,such as weight and secondary sexual traits of males.It suggested that certain phenotypic characteristics of males changing with age.However,the result of the correlation between the number of females and the male phenotype characteristics indicated that the male characteristics did not have a significant influence on the number of females in this troop.This study lays the groundwork for the in-depth study of the mate choice mechanism of the golden snub-nosed monkey and provided a certain theoretical advice for the conservation and management of this species.