title: Observation of intra-group and extra-group copulation and reproductive characters in free ranging groups of western black crested gibbon (Nomascus concolor jingdongensis).
abstract: Black crested gibbons (Nomascus concolor) are 1 of only 3 gibbon species that have been observed in long-term polygynous groups, but their mating behavior and reproductive characters have never been reported. Based on population monitoring over 7 years and direct observation for 26 months of the study groups in Wuliang Mountain, central Yunnan, we describe for the first time the copulation behavior and breeding pattern of free-ranging western black crested gibbons. The gestation period of black crested gibbons is estimated to be between 6 and 7 months. The average breeding interval is 3.5 years, with infant independence at approximately 2.5 years. We observed 2 intra-group copulations and 5 extra-group copulations. Copulations were initiated when a female gave a 'solicitation' gesture. When a male made any mating attempt, the female might refuse it. These results demonstrate direct female mate choice. Both male and female gibbons dispersed from their natal groups and sometimes replaced paired adults in other groups. We observed no evidence of infanticide during inter-group conflicts or after replacement of adults. Together with extra-group copulations, these phenomena indicate a flexible social organization and complex mating system. We also observed a male-biased sex ratio among offspring. More genetic work is necessary to describe the effects of inter-group copulation and the genetic diversity of this population.
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China; Graduate School of Chinese Academy of Sciences, Beijing, China.
authors.forename: Bei
authors.initials: B
authors.lastname: Huang
authors.forename: Zhenghua
authors.initials: Z
authors.lastname: Guan
authors.forename: Qingyong
authors.initials: Q
authors.lastname: Ni
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Orkin
authors.forename: Pengfei
authors.initials: P
authors.lastname: Fan
authors.forename: Xuelong
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000818:Animals; D002681:China; D003307:Copulation / Q000502:physiology*; D005260:Female; D006922:Hylobates / Q000502:physiology*; D008297:Male; D019370:Observation; D011247:Pregnancy / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D012737:Sex Factors; D012744:Sex Ratio; D012919:Social Behavior
keywords: Nomascus concolor; Wuliang Mountain; copulation behavior; mating system; reproductive characters