Gibbons are generally reported to live in small socially monogamous family groups in which both sexes disperse when they reach maturity. For the first time, we documented the dispersal pattern in a population of gibbons living in stable polygynous groups (Nomascus concolor) integrating 16 years’ field observation and genetic information from fecal DNA. All subadult males except for one dispersed at 9.8 ± 1.4 years of age (range: 8–12, N = 10). The last male remained in his natal group and obtained the breeding position at age 11 by evicting the original dominant male. Females reached sexual maturity (as evidenced by the change in body color from black to yellow) at 8 years (N = 4). Three of them dispersed and one obtained a position as a breeding female and bred in her natal group. We also observed one female returning to her natal group with her infant after her presumed father was taken over by a neighboring male. We identified only three mtDNA haplotypes from 22 individuals at Dazhaizi. Individuals in one group shared the same haplotype, with only one exception. Genetic results showed that the two breeding females were mother‐daughter pairs in all three study groups at the end of this study, implying some degree of female philopatry. We argue that in the case of black crested gibbons, dispersal decisions appear to represent highly opportunistic events in response to reproductive opportunities in their natal and neighboring groups.

Abstract:The genus Trachypithecus is the most diverse langur taxon, distributed in southwestern China, south and southeastern Asia. In this study, we include 16 recognized Trachypithecus species to reconstruct the phylogeny with particular concern to the taxonomy of the three subspecies of T. phayrei using multiple genes. Our results support a sister-relationship between T. p. phayrei and T. p. shanicus. However, the mitochondrial CYT B gene supported T. p. crepuscula as a distinct species, but the nuclear PRM1 gene suggested a closer relationship between T. p. crepuscula and T. p. phayrei. The incongruence between nuclear and mitochondrial genes suggests that hybridization may have occurred, a fact that would benefit from re-examination using multiple unlinked nuclear genes.

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