Postural origin theory predicts that body postures are related to hand preference in nonhuman primates due to hemispheric specialization.Foot preference,especially in manipulating objects,is also a good predictor of hemispheric specialization in humans.We studied limb(hand and foot)preferences in 11 captive adult black-and-white snub-nosed monkeys(Rhinopithecus bieti)to see how limb preference is influenced by postures and foot manipulation.Hand preference was significantly different for this group between quadrupedal standing and clinging postures,and sitting and clinging postures,but not between bipedal standing and clinging postures.Individuals were significantly more likely to use the right hand in the clinging posture than in quadrupedal standing or sitting postures.In the sitting posture,individuals maintained their respective hand preference even when the food was on the other side of the body.There was a gender difference in the sitting posture,where females preferred their right hand but males preferred their left.Individuals who did not routinely use their feet to manipulate objects,compared to those who did,shifted to greater right hand use from the clinging posture to the bipedal posture.One male individual and his offspring were more likely to use their feet to manipulate objects than the rest of the monkeys.In the present study,we reveal the first evidence of a postural effect on hand preference in R.bieti as well as a foot preference in this species.Our results mostly agree with the postural origin theory and hemispheric specialization.
Non-human primates often live in socially stable groups characterized by bonded relationships among individuals. Social organization can be used to evaluate living conditions and expansion potential. Bisexual group size, ratio of males to females and group composition are essential elements determining the type of social organization. Although the first report on Shortridge’s capped langurs（Trachypithecus shortridgei） was in the 1970 s, until now, the species only inhabits forests of the Dulongjiang valley in northwest Yunnan, China, with c. 250-370 individuals in 19 populations. To understand its social organization, we collected data from five groups of Shortridge’s langurs at Silaluo in the Dulongjiang valley during August 2012-October 2013. Family groups consist of one adult male, 2–3 adult females and up to five young. Group size averaged 8（7-9） individuals. The ratio of adult males to females（M/F） was 1：2.9, infants to adult females was（I/F） 1：2.2; and ratio of adults to immatures was 1：1.2, indicating the potential of a population increasing. Birth season was during March-July and the inter-birth interval was two years.
Ying-Chun LIFeng LIUXiao-Yang HEChi MAJun SUNDong-Hui LIWen XIAOLiang-Wei CUI
