Social functions of relaxed open-mouth display in golden snub-nosed monkeys(Rhinopithecus roxellana)

Relaxed open-mouth display serves important social functions in relation to submission, reconciliation affiliation and reassurance among non-human primate societies; however, quantitative evidence on this behavior remains insufficient among multi-level social groups. From July to November 2016, we examined four potential functions of the relaxed open-mouth display during pairwise, intra-unit social interactions among 18 free-ranging adult and sub-adult golden snub-nosed monkeys(Rhinopithecus roxellana) who belonged to three one-male, multi-female units(OMU) at Dalongtan, Shennongjia National Park China. Results showed that: compared with no relaxed open-mouth display,(1) the occurrence of displacement by a dominant individual approaching a subordinate was lower and the distance of the subordinate to the approaching dominant was shorter when the subordinate showed open-mouth display;(2) relaxed open-mouth display reduced the probability of continued attack for victims of aggression and allowed victims to achieve closer proximity to the aggressor during post-conflict periods;(3) relaxed open-mouth display by dominant individuals allowed them to achieve closer proximity to subordinates; and(4) the exchange of relaxed open-mouth display had a greater impact on the outcome of interactions than one individual alone giving this signal. These findings suggest that relaxed open-mouth display serves important functions regarding submission, reconciliation, affiliation and reassurance in coordinating social interactions within OMUs in golden snub-nosed monkeys.

Population structure of the golden snub-nosed monkey Rhinopithecus roxellana in the Qinling Mountains, central China

Environmental barriers and habitat fragmentation can restrict gene flow,leading to genetic divergence among animal populations.The golden snub-nosed monkey,Rhinopithecus roxellana,is endemic to China,and rang­es across 4 provinces.However,over the past 40 years its populations have become fragmented.We investigat­ed the genetic diversity,demographic history and population structure of R.roxellana in 5 reserves in one of its strongholds,the Qinling Mountain forests of Shaanxi.We collected genetic material from 11 monkey bands(a group of individuals containing multiple 1-male units)with a total of 428 samples genotyped at 20 microsatel­lite loci.Allelic richness and heterozygosity suggested a relatively high level of intra-band genetic diversity.We found no evidence of any genetic bottleneck in these R.roxellana populations.AMOVA and Bayesian cluster analysis revealed that R.roxellana in the 5 reserves are highly structured and form at least 3 distinct subpopula­tions.These subpopulations concur with major topographical features in the study area,such as mountain ridg­es,suggesting that dispersal of R.roxellana may be restricted by geographical barriers.

A newly-found pattern of social relationships among adults within one-male units of golden snub-nosed monkeys(Rhinopithecus roxenalla)in the Qinling Mountains,China

Group living provides various advantages to individuals in regards to protection avoidance,intergroup competition,productive success and social information.Stable one-male units(OMUs)consist of relationships between the adult females and the resident male as well as the relationships among adult females.Based on continuous observation of a reproductive group of golden snub-nosed monkeys(Rhinopithecus roxellana)in the Qinling Mountains,we analyzed the relationships among adult individual dyads within 4 OMUs.The results indicated that in golden snub-nosed monkey societies,females not only had no strong tendency to build a relationship with the resident male in the OMU but also had no strong tendency to build relationships with other females in the OMU.In comparison with hamadryas(Papio hamadryas)and gelada baboons(Theropithecus gelada),the relationships within golden snub-nosed monkeys OMUs showed neither the star-shaped pattern observed in hamadryas baboons nor the net-shaped pattern observed in gelada baboons.We concluded that the relationships within golden snub-nosed monkey OMUs indicated a third pattern in nonhuman primate societies.Future research is required to determine the potential mechanisms for such a pattern.

Kinship promotes affiliative behaviors in a monkey

In social mammals, kinship is an important factor that often affects the interactions among individuals within groups. In primates that live in a multilevel society, kinship may affect affiliative patterns be- tween individuals at different scales within the larger group. For this study, we use field observations and molecular methods to reveal the profiles of how kinship affects affiliative behaviors between indi- viduals in a breeding band of wild golden snub-nosed monkeys （Rhinopithecus roxellana）. We use a novel nonparametric test, the partition Mantel test, to measure independently the correlation between kinship and each of three affiliative behaviors. Our results show that more closely related females are more likely to groom each other. Average relatedness between adult females within the same onemale unit （OMU） is higher than that between adult females from different OMUs. We suggest that closely related females may reside in the same OMU in order to attain inclusive fitness benefits, and that kinship plays an important role in maintaining the social structure of this species.