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.
To understand the effects of the chemical and physical properties of plant leaves on food choice in Rhinopithecus bieti,we collected mature leaves of nine food and five non-food plant species at the southernmost part of the species's range.Chemical properties such as fat, ash, crude protein (CP), total phenolics (TP), and fiber content including neutral detergent fiber(NDF), acid detergent fiber (ADF), lignin, celluloses and hemicelluloses, and physical toughness were measured. R. bieti tendedto choose leaves with lower fiber content, higher ash, a higher ratio of CP/ADF, and lower toughness. No difference was foundfor fat, crude protein, total phenolics, hemicelluloses and lignin between food and non-food leaves. Even though the ratio ofCP/ADF is generally regarded as a good indicator for colobine food choice, the difference in the ratio of CP/ADF between foodand non-food leaves was only the result of differences in ADF. Since positive correlations were found between ADF and toughnessfrom all leaves (both food and non-food species), and toughness of leaves was likely easier for R. bieti to sense than fibercontent via mastication, the toughness of leaves may function as a predictor of food choice in this species.
